Replacing a 2 stroke outboard head gasket 

Thanks Stu! Just started my yamaha 15hp 2 stroke after replacing the head gasket. I'm alone, on anchor in Panama and you were my only friend for the project. Obviously it went well. Living on a sailboat in remote places, I must learn new skills every time something breaks. Thanks to people like you, it's become quite easy. Liked and subscribed!

Thanks, I swear Dangar Marine's videos are keeping my 1983 Mariner 25M running!

I lost it at "couldn't find a longer straight edge, so I guess we'll have to use this one" (holding a yard long ruler) 😂 Gotta love the dry-pan aussie humour! Great videos, keep it up!

These are easily the most helpful marine vids on RU-vid. Thanks for making them. :)

Thanks Stu for all these videos. Working on an old 2 stroke at the moment and watching your posts is great.

Once again, a brilliant video, you’re so easy to watch, down to earth, and extremely informative

I recently purchased a seized 55hp Sea King/Chrysler outboard for cheap and while I am mechanically inclined, I had never worked on a boat engine before. I started watching your videos last week and while I have done most things right so far, I have also learned a lot that will help me with the rest of the repair process. Hopefully pulling the head won't be necessary but if so, this great information will help!

Nice vid Stu, just got my head gaskets in the mail from MarineEngine to do my old 100hp Evinrude, It's amazing how often you've upload videos of the exact thing that planned to do my outboard its a big help thanks

I am 68. Been an auto mechanic, 62B10 heavy equip. mech. & small engine mech. I knew nothing about out board engines until I found your channel! Thank you so much!

You make it look so easy...Great video. Hope this will be an easy fix. Stay dry. Thanks for posting.

straight up your comment about rachetting spanners and about oiling the head bolts for proper torque are absolute key! Thanks again!

Brilliant teacher, I have always had no confidence with Engines , You give me confidence, alas I do not have the Tools you have but you explain things very well . Thanks .

Awesome as always. When I couldn't reach the lowest two bolts on the head cover to remove it, (they were really stiff & started to burr over with spanner use) I actually drilled two 22mm holes in the outer casing to provide access to them. It seems a bit radical, but I got 2 grommets to fill the holes for water-tightness, so it should be ok. I then could use a socket to remove them (one broke close to the head, which was a whole other adventure!). However, I now have much more chance of tightening all the bolts accurately with a torque wrench...

I just found your channel and I love it, I use to work at a Yamaha dealership but I wasn't a mechanic but I wanna be one day I love working on boats

Changed the thermostat and cleaned out the water pump area. Was overheating constant. Now she runs like a dream. Yamaha 80hp 2 stroke on a Shetland black hawk. Your channels amazing mate.

Thank you vary much you are getting vary popular in the states especially in Florida and the coastal s.

Great video. One comment about oiling head bolts: I was told that too much oil on the head bolt (or on the internal threads of block) can result in problems. For example if there's a pool of oil at the bottom of the bolt hole, and the bolt hits the oil - there's nowhere for that oil to go and it can throw off the torque (ie false reading because of the oil stopping the bolt) OR, more seriously, it can strip the threads on the bolt because of high hydraulic pressure. Perhaps a simple warning not to over-lubricate is what I'm getting at. Yes, oil the threads - but sparingly instead of liberally. Thanks for all your great videos!

Thank you. I bought a very similar one which came with a blown head gasket, without a thermostat and temperature sensor. You have helped me a lot. 👍👍👏👏👏

Another very well explained, step by step, well done again !

Stu - as always, thanks for keeping these old videos around. Found out this last week my 1973 Johnson 50hp is either dealing with a head gasket problem or a water jacket issue. If it's been sitting for several days, it starts and runs without issue. But if it's been run hard and warmed up, it doesn't want to restart. I took it to the shop and they cleaned and tuned the carbs but still couldn't get it to idle. After it had been running for a while, they pulled the plugs and saw that they had water on them. So there's either a leaky gasket or crack somewhere. As AvE would say, it's already fuckered so I can't make it worse so going to pull the water cover and head and see what I can see. Replace both seals and then reset the timing and see what we get ...

@5:50 You removed the coils and put back the bolts into their threaded hole. You are a great professional.

Interesting tip about putting oil on the bolts so they don't bind and give a false reading on the torque wrench, I'm still working on the 50HP Mercury but the delay is that I'm also working on the fiberglass repairs to the boat it will be going on, finally got the stingers and transom dry mounted and there a perfect fit and still waiting on the flywheel puller to arrive so I can properly repair the wires coming from the stator, which at that point I will mesure properly before re-installing it

So dang good. Nicely structured and great clear explanations. Thank you

Awesome video,Keep it up!

Hi Stu I had this on a 1990 Johnson 40 hp 2stroke and I took off the bottom ring to get bottom bolts accessible. Not that I’m saying you’re doing it wrong. After all the end result is what we are after. Thanks for all you do to help other boaters, you’re fan from Missouri. P.S. The motor would run and miss and sneeze after looking at vacuum leaks mixture settings I found the VRO system was one of the problems causing plugs to foul quickly so I bypass it. It was mixing around 20 to 1 and it couldn’t be fixed. I tested it by how much oil used to a gallon of fuel. Also resetting the timing to the factory marks and fine tuning the carburetors Helped as well.

Cheers 🍻 and ThankYou very much for the details that oftentimes these ‘do it yourself’ videos do not include, well done!!!. MoN this Rocks!! My 07’ 25mlh needs that completed soon at 91/90psi

Thank you for a great video Thanks from Canada

Nice work Stu! I'll have an outboard spring start video up in the next couple of days. I have a truck video going up tonight!

another great video!! :D i just changed the diaphrame on my 40 autolube from 93

Tip on removing corroded head bolts: Just after you break them loose - work them back and forth a bit to break up the corrosion. 1/4 turn back and forth 5-6 times will break most of the corrosion on the threads into a fine dust that is much less likely to bind the bolt, and cause it to snap. Penetrating oil after you break up the corrosion helps if the oil will flow into the threads.

Another great vid! Thanks.As to the ratcheting wrench you would like the ones with pivoting heads.Cheers from Canada

Great video Stu. I'm always nervous when removing those head bolts and still nervous when torquing them down. I've broken them in both instances. When it's all back together with no broken fasteners I usually celebrate with a much needed beer!

Great video after wire wheel. I use a pice of 1/2 inch glass with a sheet of sand paper to make it strait. Figure 8 motion. Have a good one

Just became a Patreon- you deserve every penny!

Great video. The cylinder differencal you prove that the labyrinth's were sealed between cylinders. The thermostat being out could lead the top cylinder burning cleaned. Bottom one carbonized. The back firing a sheared key on the flywheel or magnets that have moved from the flywheel. They are glue in.

This video couldn't have come at a better time haha, waiting for my head gasket to come in the mail.

good trick with the hand torque method is to use a scale on the end and read where it clicks, and do the same for the hard to reach one (same length wrench of course). On some outboards dropping the lower cowling gives better access - thanks for the vid!

I've watched this video multiple times and read through all 310 comments before I reassemble my 1991 Yamaha 115 cylinder head that had a thermostat bolt break in it, then the extractor broke despite my best efforts. I have a new cylinder head, cover and gaskets and worked very carefully to clean the block with scraping and then carefully and diligently used a bench stone to clean the remainder. I have checked and rechecked for warpage (over stoning) with an abnormally long straightedge ;-) My SELOC manual states in BOLD text in multiple sections NOT to use sealer. Stating that an even coat is near impossible to obtain and "Never, never use automotive type head gasket sealer. The chemicals in the sealer will cause electrolytic action and eat the aluminum faster than you can get to the bank for money to buy a new cylinder block." All of this conflicting info is causing my over analytical mind to go into convulsions! Since I live in Alaska and can't seem to get Hylomar and Permatex High Tack spray-a-gasket Adhesive Sealant rated to 450 degrees F. (232 C.) is the closest I can find I think I will just opt to go dry. The manual does call for Permatex on both side of the thermostat gasket so I will use the High-Tack there. The next thing to agonize over will be how to set all the bolts for new cover and top. I did get all new bolts and even replacement washers. I think I will clean the threads into the block and use the blue Loctite method, decreasing the torque value by 25% as stated here on Anti-Seize Technology site under FAQ: www.antiseize.com/Content/Images/uploaded/torque_specifications.pdf Stuart, thank you so much for all the videos you have created. Your knowledge and humor have been an invaluable asset to me. I gave you a FB recommendation, subscribed, and ordered a bunch of DM swag from your site so that me and the family can stay warm as we drift aimlessly about as I bollock-up my kicker! I lament that my late father never got the chance to watch your videos. He lived in Australia for a year and had a 39' sailboat in Washington state. He would have loved your channel! He would want me to quote Wind in the Willows and what Water Rat said to the Mole: "Believe me, my young friend, there is nothing--absolutely nothing--half so much worth doing as simply messing about in boats." Cheers Stuart! ~Ben (ps I just signed up as a Patreon, keep up the good work and have a Coopers on me, Mate!)

Hi Stu, You need to do a video on changing reeds on a 2 stroke. I'm sure there is a bunch of folks who don't know what these are

Nice video man!

Hi. Great video! As far as I know, there are different tork ratings for dry and for oiled assembly. But I could be wrong.

Just got turned on to your site and I appreciate your teaching ability. Head and shoulders above many of the sites I see on RU-vid. Thank You very much.

Thank you for making this videos are helping me

great videos danger marine! learned alot from your videos. 88 40 hp evinrude running great from you're advise

Great video, love this channel !!

Good job...I noticed you put something on the cylinder head bolt threads while reinstalling..In the U.S. mechanics often use a non hardening gasket sealer such as permatex..It prevents salt intrusion on the threads more effectively than greese.Also heads that are slightly warped can often be planed down at a machine shop..or even by hand by using fine Emory cloth sheets..with a figure eight motion..On small engines like this one..(old school) .Another old school trick is remove the inards of the thermostat so you have some restricted flow of the water so it picks up the heat..and yet you don't have the worries of a stuck thermostat..The total removal of the thermostat allows too quick a flow..and might explain the top cylinder carbon.. Carburetion adjustments and cleaning should do the trick unless the intake reed valves are worn out..rare but can cause the issue noted..Disclaimer..The correct repair on the cylinder head cooling is replace the thermostat with a new one..especially if it's a fresh water motor or in a cold climate.There are products to flush through the motor and remove...desolve salt..

Gearwrench does have ratchet wrenches with reversible drive. I have a few and the head is usually still small enough to get in tight spaces. Little pricey though. Great video as always mate.

Danger, Nice Car Buddy!

Kiwi tip: if you wind your ratchet spanner out too far...push it in and use a regular set spanner to wind the bolt back in! lol

I like that calendar!!!

Wow you make it look easy , i have an 1985 johno 70hp the water jacket was rusted on lol

Nice video but you can tell the guy is backyard trained no factory training of any kind. Which is good down to earth personality not stuck up or tryin to talk a big thumbs up bro!

This is great, thanks Stu :)

This is a really good video, thx

Great job. Well done

Cannot thank you enough for your help

I changed the headgasket on my Mariner (yamaha engine) 30hp last summer. The gasket was blown and had less than 50% compression than cylinder 1. Snapped two of the headbolts and it was a bitch to fix it. Luckily it was much material left on the cylinder so i could drill the old remains out and make new threads. Now it runs like a champ!

one way ratchet situation! LOVE IT . i have been there it is hilarious

Great video- thanks

Prying usually works, I find tapping around the edges with a brass hammer loosens it up.

Hey Stu great video very helpful i’m currently in the process of replacing the pistons in my 2 stroke yammy you wouldn’t happen to have a video with some tips an tricks on how to do that?

Awesome video

Nice calendar! Or poster back there... I'm about to pull the cylinder heads off my 1994 200 hp Yamaha. I hope I can get all the bolts out without snapping one off!

Nice a new video I've been waiting

Interesting video!

thanjs for the video but now i am in the middle of fixing one AND I HAVE TO WAIT for another video so i can fix it, Just kiddingn and really enjoy the videos keep them coming

Keep up the good work stu, I think it's brilliant that you do this for the public but you gotta put some batteries in your work shop clock 😉

I have a 15hp yammy that sometimes revs out and mostly won't, this started after replacing a stuck thermostat, it was a $100 motor that seems to have had zero maintenance for its 25 year life, I figured for a $100 it was worth it as I do all my own work. After cleaning carb, and replacing the thermostat I tasted the tips of the sparkplugs and found one was salty indicating water on the plug. It would also occasionally be seized after standing for a day or two but loosened up easily, also indicating water in the cylinder. The strange thing is compression was 125 even on both cylinders. I popped the head off to find the water jacket almost completely blocked, yet the head gasket doesn't look blown. I have ordered a new head gasket and given the cylinders a light deglazing with 320 emery paper on a drill to return some cross-hatching (I have had luck in the past doing this on small 2.5hp tohatsu/mercury's) and hopefully, this will sort the issue. My only hope is that the water is not from a crack somewhere I haven't found yet.

Nice video Stu, when changing cylinder head gaskets I usually remove the entire powerhead, take advantage to clean all water paths, decarbon piston heads, exhaust area. Install a new lower base gasket with s slight grease coating at both sides, and torque to specs. that's to be able to remove the powerhead again without harimig the gasket My motor has 4 lower head bolts impossible to be torqued with a torque wrench if powerhead reamins screwed on its base.I'm a manic about torquing all head bolts to same torque spec whichever they are. Other issue, on 2 strokes 2 cylinder motors have never seen both plugs to come out in same clean cond, the lower one usually comes out bit darker than the upper one, and that's on new out of the box motors with few run hours on them., seems it's the nature of the beast. When you torque a cylinder gasket with a torque wrench, say needs to be torqued back to 25 NM, you torque it in a single torque straight to 25 NM or in a 2 step process, say 13 on first one, 12 on the second torque adjustment.?

Great video thank you

Master of masters.. I love being ur student

In my apprenticeship the instructors always said the torque settings were for 'dry on dry' threads and to never use lubricant on the threads because you will over torque the threads, plus the bolts can vibrate loose easier due to the low friction. Where I work now we use blue Loctite or 'thread sealer' that looks like ATF and sets like a gell and the torque settings are all redone to allow for the fluid being on the threads. Looking at the tables for a 'dry' thread use and a 'sealed' thread use, 12mm bolts with fine threads are roughly 15Nm lower for wet threads, 10mm are 12Nm less, 12mm course thread are 10Nm less and 10mm are 8Nm less. Actually , those are for 'screws' , we don't put thread lock on bolts, we use the sealer on the shank of the bolts and none on the threads, but that is being picky:-) - anti vibration is by spring or star washers.

good video!

On the 2 lower head bolts. You can use a torque wrench with a dog bone wrench at a 90 degree angle and get accurate torque.

Great video. I have a suzuki dt25 1984 and its really hard to start it when cold. When hot engine starts very easy. I am thinking the CDI causes the problem. If that doesnt change the problem i will take a compression test and move onto a head gasket replacement since the outside seems rusted.

yo great vid bro love your channel. Peace

Thx so much,,,I hope that spray stop the leaking,,,

Great and informative are the old 65hp 3cld Mercurys easier to replace the Cooling Head without taking Cylinder head off and having to reseal and replace the cylinder head Gasket.

Marine engine don't ship to Sweden yet but when they do I'm gonna order!

Thanks for the Video, I'm working on changing the cylinder head and head gasket on my 90hp yamaha 2 stroke and ive been having some trouble removing the old gasket material. Ive been using plastic scrapers and a rubber wheel for removing decals off of vehicles that attaches to my drill. I still have some material left and I saw that you used a brass wire wheel for your process so i purchased one and tested on the old cylinder head but it seems to be sratching the surface so i was hoping you could suggest exactly what you used to accomplish this. Thanks in Advance Wes

If the cylinder head is stuck you can put back the spark plugs and cranck the engine (leave one or two cylinder head bolts in place but loose)

Hi Stu this video has helped me immensely chAnging my old DT25 gasket, I’m just wondering if I can use a brass wheel attached to my drill to get rid of the crud. Have you any videos on a break down and rebuild of older style Mikuni carbs?

Hey mate love the videos. Just curious if you can use a home made paper style gasket for a water jacket? (I have an old 9.8 merc that had a blockage in the water channels). Also any chance you could do a video on how to remove broken bolts if you break off a head bolt etc. that would be super interesting and something many people encounter.

Thanks, this was helpful!

Gday mate good video ,when i did my 50hp triple i changed the sacraficial anodes in the block ,i didnt see any in this 20 do they not put them in smaller engines ? i also cleaned as much of the water jacket on the block as i could with a wire brush on a dremel tool handy piece of kit that anyway 2 strokes as you say are fairly easy to work on

Thank you, I am taking a 25 hp Nissan apart due to top head gasket failure, leading to top over heating, loss compression, 85 top and 125 bottom. Top cylinder wall scratched lightly. I wish I could bring both to 120 to 125.

Great vid ..Thanks 😊👍🙏

Hi Stu, been reaching these head water passage videos again. I'm diving into this for the first time on a 3hp Evinrude 2 stroke. You mentioned the step on having the carb shutters wide open to preform a compression test. I think the reason for this is to rule out defective reed valves. It may affect the readings. I'm new at this internal stuff but thought I would point out the reeds may affect compression?

Great video your description and explaining is so easy to understand - I’m new to boat engines very familiar to 4 stroke car engines . So you are really helping me to get confident to get a boat and engine and keep it running great 👍 can you recommend a good 100hp outboard and/ or bigger to start my boat life?

17:15 Nice calendar 😅

Thanks for these fantastic videos. I watch them for hours. Please produce a video or link to how I can reseat the heads on my year 2000 Johnson 115 2-stroke motor. It is leaking slightly at the top inside of the starboard head. It uses sealant rather than a gasket and I need to know the best sealant to use, exactly where and how much to put on. Thanks again.

Great Video, i'm replacing a Mercury 60hp head gasket. What does polymer do when you spray on both side of the head gasket? Thank You

I love the videos mabey you could do a video on a dirt bike

Your videos are amazing. My son and I just bought a 2001 Yamaha 15 HP 2 Stroke (15MSHZ) and cleaned and rebiult the carb after seeing your great 40 minute video. Also replaced gaskets in fule pump after seeing your other video. 2 quick questions: 1) You mentioned about danger to the iginition coil if ignition is on and it is disconnected but not grounded. Is that mostly for prolonged periods? I ask since in this (or another video) you removed the plug from each cylinder one at a time while the motor was running to check each cylinder and I have done the same thing a lot on my "new" motor (see point #2). So is it OK to do that as long as not done for a prolonged period? 2) I wish you could do a video (if not already done) where you explain the crankcase breather hoses and what they do and related issues that come up. Especially using that 15 HP Yamaha you have done a lot of videos with. I ask since our bottom cylinder stopped working a week after we bought the motor. It was not spark since the bottom cyl did not run using the same coil switched from the top to bottom. Plugs switched did not help. Carb (only one on this motor) was clean and top cylinder idled and powered up well. When I pulled the top and bottom breather hoses off and sprayed carb cleaner and compressed air through them, the bottom cylinder fired right up!!! So I fixed the problem but do not know why it worked. Please help me understand if you have a minute. Thanks again for your great videos!

I was surprised after seeing vids of people removing the head like you did and looking at the pistons ect...to realize my 50 merc is a "headless" outboard. Its the strongest stock 50 2 stroke ever made at 59ci(yamaha is like 42) which I'm happy about but I think it sucks I can't remove the head like the other motors. Apparently if I ever want to rebuild this motor I have to find a very knowledgeable machine shop who can bore "blind cylinders". Have you ever had to mess around with a headless outboard before, lol?

Thank you

Hey Stu, Thanks to your excellent videos, I just replaced the head gasket and thermostat in a 1984 Johnson 40 HP. I did not do anything to pistons, rings, etc. Do I need to follow all the standard break in practices (fuel mix, stepping up RPMs over time) or is the break in for a just a head gasket change more abreviated? Thanks again !

Stu, I have a Johnson 50 hp. I see some white stuff (salt? corrosion?) around the head gasket near the lower cylinder. Is this the sign that something is wrong or normal occurrence in salt water? Motor starts easy and runs fine. Thanks for the great videos!

good stuff

Lower head bolts might be tighter for reason you said, they Need different tool as in box end wrench. So tightening box end by hand might be tighter than uppers used with torq wrench?