Different Shaft Lengths on Inboard

[tullydf]

Last year I had a shaft replaced by a hauler whose trailer bent my previous shaft upon removal of boat from water. When the job was completed and I was prepping the shafts, rudders, and props for launch, I noticed that the new shaft was about 3/4" longer than the other side. I took the measurement from the strut to the prop hub. The original was about 2" and the new shaft about 2 3/4". As a result, the prop is 3/4" closer to the rudder on one side than the other.

Does anyone think this will pose a performace, vibration, or safety issue?

 

[Don S]

Re: Different Shaft Lengths on Inboard

Try it and find out, if you have problems take it back and tell them to fix it right. Or just call them up and tell them it's not right and ask why it's too long.

 

[Ned L]

Re: Different Shaft Lengths on Inboard

Potential issues would would depend on what kind of boat, the shaft diameter, normal operating RPM, ..., ... - I would have them make it right. It's not difficult to do. Pull the shaft, cut off the top end, cut a new keyway, install the shaft. For a 'typical' boat I doubt you'd notice a difference, or if you do it might be in vibration, not in performance or handling.

 

[tullydf]

Re: Different Shaft Lengths on Inboard

Ned,

It's an '88 36' Mainship Nantucket Sedan. It has twin crusader 350's and my normal operating range is between 2000 and 3000 RPMS. I did use it this way last year and could not be sure if it was a factor. By the time I got out on the open water en route to Block Island, the boat had been in the water for weeks and I tried grease on my running gear which was completely ineffective. At Block Island I notice barnacle growth on the shafts, props, and rudders. That could have been the source of lower speed and vibration.

If it is a problem, I am hoping that there is the possibility of having the shaft shortend from the engine coupler end and that there would still be enough of the keyway not to affect anything and then the shaft pushed in to make up the difference.

Does that sound at all feasible?

I also fear that going after the hauler will be like getting blood from a stone.

 

[tullydf]

Re: Different Shaft Lengths on Inboard

Ned,

Also, the shaft is 1 1/2"

Dave

 

[Grub54891]

Re: Different Shaft Lengths on Inboard

My first question would be,is the shaft installed all the way into the coupler? I would hope so. If it is it needs to be shortend as stated above.
Grub

 

[tullydf]

Re: Different Shaft Lengths on Inboard

It appeared to be installed completely into coupling. I'm hoping of the possibility of doing this without removal of the entire shaft. There is good access to it and about 4 feet in length before going out though packing nut.

 

[Capt Ken]

Re: Different Shaft Lengths on Inboard

Have you unbolted the coupling and slid it back far enough to be sure it's all the way in?

 

[tullydf]

Re: Different Shaft Lengths on Inboard

I have not...the boat is on dry dock in Shelton CT under 18 inches of snow right now. I was worried about loosening the coupler thinking I'd throw something out of alignment.

 

[Lyle29464]

Re: Different Shaft Lengths on Inboard

I would not worry a bit about it. ( If your sure it's in the coupling all the way)

 

[Don S]

Re: Different Shaft Lengths on Inboard

I have not...the boat is on dry dock in Shelton CT under 18 inches of snow right now. I was worried about loosening the coupler thinking I'd throw something out of alignment.

Why don't you just ask the shop that installed it, instead of a forum.

They may just say something like, "Hmmm that shouldn't be, let us have a look at it."

 

[tullydf]

Re: Different Shaft Lengths on Inboard

It was not done by a shop, it was done by the hauler who damaged it. I told him about it, and his response was that it shouldn't be a problem. It was tough enough getting him to admit it was his fault. I had to produce pictures of his trailer pad resting on the shaft to finally get him to react. I could likely take him to court but I'd win the battle and lose the war.

I was really hoping just to come across someone in the know who might have the knowlege to know if it would be a problem or not before I take the next steps. If it must be fixed, I could try the hauler, but he takes forever and look what I ended up with in the first place. I just want it fixed by someone who knows what they're doing.

 

[tullydf]

Re: Different Shaft Lengths on Inboard

By the way, he does do shaft work and he used H&H for the new shaft.

 

[Capt Ken]

Re: Different Shaft Lengths on Inboard

Unbolting the coupling will not mess anything up. Just take the four bolts loose and wiggle the shaft back and take a look. I would think the machine shop that cut the shaft used the measurements of the old shaft.

 

[tullydf]

Re: Different Shaft Lengths on Inboard

Ken,

That's what I would have thought also. unless the hauler provided the dimesnions and got it wrong. That is what I fear. When I questioned him about it, you'd have thought he'd of said, let me take a look and make sure we got it all the way in. I hipe to get to the boat in the next week or so. CT roads are a mess from the blizzard. The marina where the boat is may be inaccessible.

Thanks for the input.

 

[Ned L]

Re: Different Shaft Lengths on Inboard

Sorry I didn't stop back here sooner. As for vibration on the way to B.I. I would look at the barnacles on the prop for vibration and loss in speed LONG before one shaft being 3/4" longer than the other. And I wouldn't think 3/4" on a 1 1/2" shaft on a 34' Maineship would be any problem (it certainly wouldn't relate to a loss in speed). If you wanted to take care of it, yes, cutting it off the forward end would be the way to go (as discussed above). Have you checked the coupling alignment since the new shaft was installed? If the coupling face is not 'square' that could cause vibration. (Unbolt the shaft coupling from the engine and see what kind of clearance you have between the two faces as you work around the perimeter. Maximum at any point should not be more than .003",) A wild shot, but is there any chance a strut was bent too?

 

[tullydf]

Re: Different Shaft Lengths on Inboard

Ned,

Strut was fine. I was concerned becasue while there was a vibration, I visually inspected the shaft from inside as I was adjusting the packing nut underway and the shaft had no wobble whatsoever. It was straight as a pin throughout the RPM ranges. I was concerned that with the prop being 3/4" closer to the rudder it might be creating too much prop wash on rudder as viration seemed at extreme end and not from shaft itself.

Like you said, it could have been the growth on the props and shafts combined. I may just have the mechanic at the marina in the yard where I am keeping the boat (Shelton, CT), just go ahead and fix it. I don't want to get into a situation where I launch it and find out it was not the growth and pay to have it hauled again.

 

[Grub54891]

Re: Different Shaft Lengths on Inboard

I know this thread is getting older but I saw one the other day that had a vibration last fall.I inspected it and found the keyway @ the prop was not deep enough for the key,making the prop sit crooked on the shaft,not much but I could see the gap a bit,I removed the prop and fitted a new key,lapped prop to shaft,and I belive it'll be good to go now! Just something to check any time a prop or shaft is changed out. This one had the prop changed in the water late last summer by a diver,I'm shure he could not see the problem from under there.
Grub

 

[tullydf]

Re: Different Shaft Lengths on Inboard

Thanks all for replying...I launced the boat last week. I put fresh paint on the bottom and running gear. It ran beautifully and there was no longer any vibration. It must have been marine growth as last year I used grease on the running gear and it absolutly did not work. I did spend many hours removing the marine growth/barnacles from the running gear prior to painting with trilux. So far so good!

Dave

 

[Ned L]

Re: Different Shaft Lengths on Inboard

Real good news! Enjoy the season.