A Volvo Penta I/O propeller shaft was bent to 0.052" (the propeller was noticeably wobbling), and I was able to successfully repair it to a runout of 0.002" using a jack and a mechanic dial indicator. No heat was used at all.
Many thanks! This worked great! I took my bent shaft from .115 to .003. Your instructions were perfect. I didn't buy the locking flexible type clamp that you had, I had to set up the two swivel system which was much trickier,.... I wish I had the locking flexible clamp! Thanks again!
As a marine mechanic for 30 years I HIGHLY do not recommend this! You are at risk of damaging the seals, bearings, the casting and a whole lot of other things. Just spend the money and have this done the correct way!
@@TheGaboon01 not really, i think; if the bearing did not get damaged with the first underwater hit,it won't get damaged by the SAME force in the other direction; and i find it funny people talking about the seal!! the shaft cannot move much ,where the seal( flexible rubber) is, so the seal will stay as it was before; and another thing: if the force was too grate to the point of the ball bearings/rollers indenting the races, you'd feel it rotating the shaft in neutral by hand, and you'd hear the rumble and whine when you ran the boat in gear on land, on the muffs.
@@josepeixoto3384 And I would replace the seal anyway if I thought it was a problem, that is still a very easy job compared to pulling the lower and then pulling the prop shaft. Don't get me wrong, I have done it, but I would do this if the bend wasn't over .125"
As a marine technician I never seen that before. Haha ok....😅 Hopefully his seals don't leak. The guy's lucky or he would have been paying more money if you would have broke a case. I wish you could have ran the engine and give us an update after running on the lake.
I know this is an old video, but I gotta say it is still working perfectly! I bent the prop shaft on my Suzuki 200 and used this method to fix it. From .0190 to .0017! Time was about 5 beers or so. I still can't believe it works so well for being so low tech; another $800 saved because of this video! Now to find a skeg and prop repair video...
I took a long breaker bar that slid over the shaft and nut and applied manual pressure and got mine less than .002 out but it took about an hour of messing with it.
I commend you on your innovative approach to solving the bent shaft problem. I have A couple of observations based on the video and other comments below... 1) waiting for a period of time while the force is applied does nothing. Steel does not creep at room temperature. 2) Once you reach the elastic limit of the shaft it will start to bend immediately with further force. You always have to overcome the deflection first when making a further correction. 3) Applying force with the dial gage installed is essential. Once you get the feel for how much deflection is elastic any further deflection is actually bending the shaft back into place (called plastic deformation). This is what you're after, but you don't want to bend it too much. 4) A lot of comments warning of damage to bearing, housings, seals, etc. First of all, if you have a bent shaft, the bearings, shaft, and housing have already experienced these high forces due to the event which bent the shaft in the first place. Bending it back does involve risk, but it is a calculated risk. 5) Seals are very compliant, they should handle such displacements easily. 6) Brinelling of the bearing race is a possibility, but the original event would have also caused this if it happens. The prop shaft on my Mercury 850 had 0.040” runout. Bad enough to be very noticeable to the naked eye. Applying this technique using a stubby bottle jack, board, and steel plate to spread the load I was able to get it down to 0.001” runout with no damage to any components! It took only about 1/2 hour and no $$ other than the jack.
Excellent comment. I will be doing this to mine... turning the engine off in the water while it's in drive you can hear the prop contacting the shroud while the prop slows down.
1) True 2) True 3) True 4) Dead wrong. When a prop strike happens the boat is in the water, the instant it made contact the rubber inner prop hub flexed, (if equipped) the motor was pushed to the other side, and the boat moved in the water, this all equates to a massive amount of "give", or "cushion" to the strike. The bend happens in a fraction of a second of high load at the instant of contact with the rock. What he's doing here is EXTREMELY risky and damaging the bearings for SURE. He's VERY lucky the upper or lower case did not explode in his face, they are NOT designed to have these types of forces applied in this way. 5) Yes and no, they are not designed to have this much prolonged pressure on one side. 6) Wrong again, see 4 above. The prop strike has to be very severe/under high load to damage the bearings, this repair "method" is WAY more damaging to the bearings than the initial strike that caused this slight shaft bend due to the massive, prolonged pressure to one side with zero give/cushion during the event of trying to bend it back. At the end of the day, this obviously works, but almost everyone is causing more expensive long-term damage to the internals (bearings, seals etc) and risking destroying the motor case, and injury. Just don't do this kids. If you can afford a boat, you can afford to fix it right, or pay to have it fixed right. People need to learn when and where to use which type of prop to avoid bending your shaft in the first place! Aluminum props rarely cause bent shafts and are for open water and no hard obstructions like stumps. If they hit anything, wood or rock, they will break/crack/chip/bend (by design to save you from expensive motor damage) and have to be replaced. They are cheap to replace if you clip something. Stainless steel props are for open water speed boats, and shallow water slow/idle speeds (like during fishing) with lots of wood obstructions like stumps. They can handle wood strikes without damaging the prop or shaft 99% of the time if at idle speed and not blatant or severe/under load/on plane etc. I currently live on the SE coast and bass fish inland freshwater rivers FULL of stumps, trees, and wood obstructions all over the place in the middle of the river half the time. I have bumped dozens of stumps/trees with my stainless prop at idle speeds with zero issues. Last Saturday I clipped a rock near a bridge next to I95 that should not have been there, destroyed my SS prop (They can be repaired, aluminum props cannot) and bent my prop shaft, because SS is much stronger than aluminum, so when they get broken from a rock, they also bend your prop shaft and/or do worse damage in the lower unit. I was very unlucky and there are virtually no rocks where I currently boat except this one area and this rock still had no business being out in the open where I hit it. When I move back to inland VA/NC next year where the rivers are all rock and never stumps anywhere let alone in the middle, I will be switching to aluminum as rock strikes are obviously common there, or I will swap on a jet drive lower unit if I can find/afford one to avoid the issue entirely. Right tool for the job people, you don't need expensive stainless-steel props unless you meet the criteria I mentioned above, stop wasting money and risking damage to your motors.
Be better to make sure its straight at the bearing end then find out low spot....heat and quench to straighten in line with low spot on true circle....could bust housing this way.
Stoooopid good video. Thank you. Zero impact on the bearings. This is the way to do it. Sure you could bring it to a machine shop and do it “the right way” but hell… Your way will save you bunches. For my 92 Johnson 40 they want 500+ for the shaft alone. 😂 HARD PASSSSS. Sure, if you’re 90 miles out and your life depends on it…. Maybe? But I’m putting around the lake on a pontoon
How do you know if straightening the shaft at the point that it's bent? The bend could be inside the case (most are) and you're just counteracting it with ANOTHER bend outside the case.
That's a great question! I can't say I know the answer to that! I hadn't really considered that to be possibility, and I know I was taking a big risk in bending the prop shaft, but I was okay with that since my fallback plan was to have a professional replace the prop shaft. I'll be curious to run the dial on it again as soon as it warms up enough to get back on the lake to see how it's doing!
I think the propeller holds most of the shaft straight and the bend comes where the propeller ends where the thrust washer and bearings start..The bending moment is biggest where the bearing is when using the jack. I think...
Are you insane?! You are putting a lot of force on a stainless steel-shaft about a foot long while bearings, oil-seals, transmission etc. mounted in an aluminum housing(!) are what holds it in the other end. Don't do this people!
Great video! I am going to try this on my 90 yamaha four stroke, It’s not really worth the $800 to fix, it has 1800hrs on it, and I’ve been ignoring the wobble for 12 years, but it needs new seals now, so we’re gonna go full cowboy on it!!!
Thanks for the video I never would have thought of this. Got my prop shaft down to .002 from .023. After a couple lighter attempts with no results I decided to apply more force and thats what finally got it to straighten. Thanks again this saved me a lot of money.
100% correct. They just don't understand the simple physics of a prop strike in the water, vs static sustained load using this "repair method". Stupid is as stupid does.
I feel like this is a dumb question, but I'm about to attempt this and am wondering how do you know which spot on the shaft to initially place the dial?
@@mbwtrpolo Got it, so I attempted this the other day and when I spin the shaft the dial pin won't stay put. Looking for opinions, do you think that means my shaft is warped so bad I can't straighten it?
Ben Henson When you put the dial indicator on the shaft, you should be able to identify a low point on the shaft and a high point, with a linear difference between the low and high as you measure it.
Tried this on my bent shaft Mercury 25 HP and got it down to .003. I stopped at that point and called it good enough. I didn't measure how bent it was at first, but it was pretty bent.
I tried this on my 150 Yamaha, didn't work. Nearly caused further damage. 2.5 ton jack can explode your lower unit. That's more than a few grand at best. As Christan said, spend the money and do it right. In NY my scag replacement was $325 and the ss prop fix was $285 at the prop shop. The dealer performed prop shaft replacement (prop shops don't dis and re-assemble) is $920, included new shaft, new water pump housing and impeller no new gears and 3 hrs. labor. If you boat, at some point, you will find the bottom! Tight Lines
Hi Thomas I am located in NY as well and just stumbled on this video. It is that time of the year and would like to correct my shaft. Are you able to forward the shop info to me. Thanks Soo Much!!
Great ingenuity brother. I was waiting for the BIG POP but success. Who says you can`t fix it with house hold tools, saved you a lot of CASH and down time CONGRATS.
+TurboGSR96 Nice work! That's great you were able to get it so close! Yeah, it definitely takes quite a bit of force to bend the shaft. But when you actually look at what the whole shaft length is, you see that only a third or less of it is exposed, so bending just that part is fine since so much of it is still supported in the housing. I'm glad you were successful! My outdrive oil is still water-free!
Wow, I can only imagine the forces exerted on the foot casing and seals and bearings. I realize you didn't want to go through the troubles to disassemble the foot to get to the bent prop shaft and straighten externally, but you really applied a lot of forces on the case and everything else. IDK
I was thinking this same thing but I believe the logic here is the shaft was bent at some point and it survived those forces without cracking the case.
@@ronaldwatson3348 Everyone is looking at this wrong, he's EXTREMELY lucky he didn't explode the case. During a prop strike there is a BUNCH of give, the motor moves, the boat moves in the water, so the force is not that high that bent the shaft. It also happens in a fraction of a second, the motor moves and boat is pushed away in the water. This guy is putting prolonged stress with NO give at all, on the shaft bearings, seals, lower unit gear case, and upper case with the wood and jack. Literally everything about this guys "method" is a bad idea. If that jack where to slip it could kill or maim him, let alone further damage or even total the motor. There are plenty of home mechanic "methods" that work, some are safe, some are not, some are fine and ingenious, most are dangerous and foolish and results are 50/50 at best. Do the job right or don't do it. Don't be a Darwin award participant, let alone winner.
Nice video. A few questions : how is the bearing/seal/gears affected by this ? You think there will be more serious problems in the future? Where did you get the dial and how did you mount it ?
Great questions! So before I went and did this, I did research and read and looked everywhere I possibly could on forums, threads, and websites to figure out how the pros and boat shops do this. I found a few different places (like "The Hull Truth" and "iboats") where people commented in a thread saying that they had used a long piece of pipe to bend the prop shaft straight, or other ways. The one thing I read that finally gave me the confidence to just go ahead and try it was one guy who worked at a shop said that they had bent multiple prop shafts straight again and had seen the boats again at the shop years down the road for other, unrelated to propshaft, maintenance and repair issues, and the propshaft they had repaired was still true and the bearings and seals were holding up just fine. I figured if that was true and I was just bending the propshaft straight again with no heat and very carefully with that dial indicator, then the worse thing that could happen was that the seals went out or the bearings went out and I needed a new propshaft anyway. Someone in my town (Boise, Idaho) quoted me $700 to replace the shaft and seals, so that was worse-case scenario. After doing all the reading I've done, I really developed a trust that the Volvo-Penta outdrive is very robust and could take that kind of a beating. When I bought the boat a year ago, I was pretty new to boats (though I'm pretty inclined mechanically, so I checked the engine really closely), so I didn't even know to look at that. I was just happy it had a stainless steel prop and left it at that. The propshaft has probably been bent for years and would probably still be fine for years, but I've read it puts a lot more stress on drivetrain components when its bent like that. I took it out just yesterday and it felt a lot smoother and I've pulled the dipstick for the outdrive oil and there's not a hint of water in it. Of course I wouldn't trust that just once or twice running in the water would prove that the seals were perfect, but if I had ruined them right out of the gate, I would see that looking at the dipstick if the oil was foamy. tl;dr: So I don't think I'll have any serious problems from that in the future! The dial seriously cost my only $27 from Harbor Freight, and its the kind that came with vise-grip-type pliers and a cool flexible arm that stiffens up when you throw a lever. That way you can use a rag to vise-grip to the fin above the propshaft and then use the arm to put the dial indicator right on the shaft. I think it's pretty important for the dial indicator to say on the propshaft as you bend it back so you aren't having to put the indicator back on every time, and you can see just how much you're bending the shaft in the opposite direction from the bend as you go along. Good luck! I hope it works for you too!
+Cameron Crawford , awesome, thanks for the detailed reply. I have an Alpha 1 outdrive, but I think it can too take the stress of this procedure. Seen a few videos on RU-vid where people do the same to them. sorry for picking your brain so much, but had 1 more question. Does it matter if you measure at the tip of the shaft (where the thread is) or at the middle of it where you did ? I suppose the readings would be consistent but if the bend is closer to end, it would throw them off. thanks again, nice job
No problem! Yes, I think the Mercruiser outdrive is similar in that regard. I think it might be easier to replace a prop shaft on it than the Volvo Penta too (at least that's what I recall from all the research I did). You're definitely right about there being a difference in where on the shaft you measure and the amount of runout you see on a shaft like that. I chose the point on the shaft that was as far out as possible, but where you have a great, smooth surface for the indicator probe to ride on. I recall reading something where someone asked that and that was the point they measure the runout on too, so I figured that even if it wasn't dead nuts at that point, it would be pretty hard to measure a couple thousandths at the very end of the shaft with the threads and everything. So I feel pretty good about getting to the two thousandths, even if the very, very end of the shaft is one or two more because of the extra length. I looked up what a propeller shaft for the Volvo Penta actually looked like outside of the outdrive, and its much larger diameter in the outdrive housing than the shaft that you bend on the outside, so when it bent originally (I hope!), it would have been the outside part of the shaft that bent, not the inside, especially since its got great support by the bearings as well. So bending it back should be bending the length of the shaft outside the drive, not the inside. Thanks for your compliment! I found a couple videos on the topic during my search and felt like I might be able to add a little to the universal knowledge for the next person to benefit from!
Did you ever measure the deflection at the end of the shaft? I know you got yours to within 0.002" but that was in the middle. I used this method to bend mine back after hitting rock (it was out by about 0.130") and i got mine at the end to be within 0.004" which to me was good enough (i don't even know what manufacturers runout spec is). Thanks for posting this it really helped. I come from an aerospace background and i know for a fact the bearing races & balls material are much harder than the shafts that they are fitted onto, so i would not be worried about damaging the bearings with static loading, but i was worried about the seals. fater seeing the comments i was comfortable doing this. Do you have any feedback on your fix? any troubles yet?
Nick325J Hello there! To answer your question about deflection at the end of the shaft versus the middle, where I measured, I did not ever measure at the end. I wish I had now! I think when I winterize my boat in a couple weeks here I'll do just that and let you know what I see and if it's held after the last two seasons. I'm glad you were able to bend yours back so well! 4 thousandths at the end of the shaft seems pretty good to me! Thanks for the input on the bearing races and collars, that definitely helps reassure me in my assumptions and research. As far as whether the seals have been compromised or if there ever has been any ill effect from the repair, I've had no troubles or issues at all! The outdrive oil has never shown a trace of water and everything has been fine. My plan always was to try and fix it and if I broke it, I'd have to pay anyway, so it was worth a shot! Happy Boating!
