V Drive Shaft Bent

Jmoore007

New Member
Mar 8, 2016
3
Knoxville
Boat Info
2003 Sea Ray 320 Sundancer
Engines
350 Mag Mercruiser V drives
I just bought a 2003 sea ray 320. When I drove the boat to the dock to be taken out of the water to be bottom painted I noticed vibrations in the boat at full throttle. This boat has V drives. Once out of the water the mechanic said the both propellers were bent and had nicks in them and needed to go to he machine shop to be reworked. Fine, $700. Then he said he measured the shaft tolerance and one was within the .003 max tolerance and the other shaft was just outside at .004. $2500 to replace shaft. It is so close to max tolerance is this replacement really necessary? If the new props solve the vibration problem do I still need to replace the shaft? Boat has 195 hrs on engines. Thanks.
 
Seems like these problems should have turned up in the survey...

The re-finished props will likely solve most of your vibration issues, but we'll wait for Frank W. to chime in on the shaft tolerances.

Congratulations and welcome to CSR!
 
I am traveling this week and don't have access to my files or manuals so I can't help with the tolerances.

However, only .004" runout isn't a lot. A good machine shop that makes marine shafts should be able to get that one back in tolerance. The problem in not addressing it is that this particular shaft….320DA and 340DA…..is known for metal fatigue snapping off the prop end of the shaft. If the shaft bend is near the prop end, this could be a lot more expensive than just shaft if it breaks and you lose a prop.

Finally, $2500 for a single shaft is stupid money …about 2X what it should be…….haul out $200; Shaft made locally $700 ($1300 from Sea Ray…..freight!) 3 man hours labor ($375)
 
I have a friend who bent his shaft on a strait drive boat. He got it straitened by a machine shop. All is well now.
 
My dock neighbor bought a 320 last year and the shaft broke in the coupler while moving the boat from bow in to aft in at his dock.The place that made the new shaft said it was a popular shaft break and he had them on the shelf ready to ship for $750.
 
I am traveling this week and don't have access to my files or manuals so I can't help with the tolerances.

However, only .004" runout isn't a lot. A good machine shop that makes marine shafts should be able to get that one back in tolerance. The problem in not addressing it is that this particular shaft….320DA and 340DA…..is known for metal fatigue snapping off the prop end of the shaft. If the shaft bend is near the prop end, this could be a lot more expensive than just shaft if it breaks and you lose a prop.

Finally, $2500 for a single shaft is stupid money …about 2X what it should be…….haul out $200; Shaft made locally $700 ($1300 from Sea Ray…..freight!) 3 man hours labor ($375)

Yes - I pulled my shafts last year and had them sent out to check for true and it was $100 per shaft. As part of the service they would take care of any "tweeking" needed.
 
Thanks guys for the advise, very helpful.. Gonna run it with the new props and get another bid regarding the shaft.
 
Can any of you guys recommend a mobile mechanic in the New York metro area that is very well versed in these matters? Il love to have my shafts and seals inspected. My props are reconditioned annually but nothing else.


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Not wanting to beat u anybody but we kind of "glossed over" the survey part. Jmoore007, did you have a survey performed prior to purchase? If no, I just want to use this as a classic example of why surveys are so important. If you did get a survey and the surveyor missed this I think I would be paying them a visit.
 
And from a technical aspect one can't really tell if the shaft is bent by measuring TIR in the boat unless it's a real visible wowie; at best that measurement is a rough indicator to determine if the shaft needs to be pulled and have a more detailed inspection. When in the boat and bolted up the non-linear stresses are not known on the shaft. For example the coupling if not perfectly aligned will show a deflection in the shaft when in fact the shaft may be perfectly straight. Conversely, if you disconnect the coupling the simple cantilevered weight of the shaft will show a very large deflection. The bottom line is the shafts need to be pulled if you feel 0.004" TIR is a problem and sent to a shop that can get them on a set of centers and run them out properly. Lastly, it's important to turn the shaft in the boat by hand; much can be determined by doing this. The shaft should turn smoothly and consistently when rotating by hand; if it's notchy or has sticky areas when turning that is also an indicator that there may be issues.
 
Thanks for the post. The props are getting reworked this week. I will be at the yard next Thursday and talk to mechanic and do the hand test. We are then going to put in the water and run the boat to see if main vibrations have been fixed. The props where in bad shape. The mechanic said when he takes props off he has to do the tolerance test to cover his butt in case the boat is still vibrating when the new conditioned props are put back on. 0.003" being max tolerance. One shaft was 0.004". Sea ray manual says the coupling can be within 0.005" max. So hopefully I am ok without the expense of replacing the shaft.
 
I wonder what a "tolerance test is"? New one on me.. Suggest when you put it in the water to loosen the coupler bolts and take gap measurements all around the coupler mating flanges so you know if the engine/gear are aligned properly with the shafts. It's quick and easy insurance and if aligned correctly will eliminate a potential source of wear, stress, and vibration.
 
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A tolerance test is done with a dial gauge that is mounted touching the shaft. As you spin the shaft, it measures the deflection of the shaft at that point. I believe this is performed at various points along the shaft to determine if any point along the shaft has a bend. I'd like to have mine professionally tested just to know.
 
A tolerance test is done with a dial gauge that is mounted touching the shaft. As you spin the shaft, it measures the deflection of the shaft at that point. I believe this is performed at various points along the shaft to determine if any point along the shaft has a bend. I'd like to have mine professionally tested just to know.

That's actually the shaft TIR (total indicator run-out) from a machinist and tooling aspect.
Here is a video I found https://www.youtube.com/watch?v=s-UG2CZ8VMM
 
I know this is a old form but hoping to chine in a little or get some info.... Last year I hit bottom and dinged the prop up good.... Fixed the prop still had a vibration, so this year i brought the prop and the shafts to the prop guy..... He put them on a dial and says there fine... Didn't check them with the lazer. Now i put everything back in and the hatch still raddles and feet vibrate... I'm thinking the shafts are bent around the shaft seal and he didn't check that part?? Is it possible?? Gonna go down and check alignment and motor mounts tom.... But that bad of a vibration could it be a bad alignment? They look like they meet perfect...
 
I know this is a old form but hoping to chine in a little or get some info.... Last year I hit bottom and dinged the prop up good.... Fixed the prop still had a vibration, so this year i brought the prop and the shafts to the prop guy..... He put them on a dial and says there fine... Didn't check them with the lazer. Now i put everything back in and the hatch still raddles and feet vibrate... I'm thinking the shafts are bent around the shaft seal and he didn't check that part?? Is it possible?? Gonna go down and check alignment and motor mounts tom.... But that bad of a vibration could it be a bad alignment? They look like they meet perfect...


Did you check the cutless bearings for wear when you had the shafts out?
Possibly a cylinder misfiring on one of the motors.
 

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