Mercruiser drive or prop?????

[water_rat03]

I was approached by someone today to look at his boat. I don't know a lot about it, but will tell what I know.
It is a 77 Bonanza, 140hp with the older style drive. There is a sticker on the drive with 140 printed on it. The top cover of the drive looks different than most I have seen, it has bolts instead of the philips screws. The bolts that take a 12 point, or star type socket.
The owner said he took the boat out (don't know how long ago) and it ran good but overheated. He replaced the thermostadt, took it out and it still ran hot so he took it to a marina to get it fixed. They put in a new impeller in the drive. He took it back to the lake and it ran good, didn't get hot, but would not as he put it (go fast). Basicaly at wide open the engine rapped up good and ran smooth but the boat would not get up on plane.
He took it back to the marina to have it checked out. They must have pulled the drive off because they only put 2 of the nuts back on. The bellows also have a hole. The mechanic told them it would be 1700 to fix, that it needed a new drive.
While I was there he started it and it ran good. Went in and out of gear fine, the prop turned like it was supposed to. He said when it was on the lake running slow there was no noises from the drive. It wasn't grinding or jumping out of gear.
He said the mechanic told him that it was running slow on the water even at wide open throttle because the gears were worn. He told them it needed a new drive upper gearbox and a new lower drive because it needed a new prop shaft. I didn't see any oil leaking, and grabbing the prop shaking and turning it it felt solid.
So, is it possible that worn gears in the drive will cause it to run slow on the water? Without any noises of gears grinding? Can the mechanic tell it needed new gears by taking the drive off the boat or the top cover off? Or is the mechanic wanting to replace the drive because the bellows were worn out and water may have entered the drive?
I have heard the prop has a hub that can go bad that will cause this. Is this more likely the problem with not getting up on plane? If so, is there a way to test these and see if they are bad?

Thanks for all the help!

 

[water_rat03]

Re: Mercruiser drive or prop?????

Anyone have any ideas?

 

[jerryjerry05]

Re: Mercruiser drive or prop?????

Yea go back and kick that mechanic/previous owner.You do not loose speed because the gears are worn down!!!He saw $$$$$ signs.
The gears that he's talking about.They don't wear down they get destroyed.
You need to find a mechanic that ain't gonna lie to you.
You can't tell if the prop shaft is bad by looking at it.
If it runs and the motor revs up then it's probably the prop needs re-hubed.Put on a different prop.
Drain the oil in the lower unit.Check for water/milky oil.chunks of metal.
You can remove the top cover and see what condition the gears are in.When you replace it,tourqe it to 20ft#.
What bellows has a hole in it?The u-joint or the exhaust.You need to remove the drive and see if there is water in the u-joint area.That's not an easy fix but can be done.Keep us posted.J

 

[water_rat03]

Re: Mercruiser drive or prop?????

Thanks a lot for the reply.
It isn't my boat, although the owner is talking about selling it. The interior is removed completely, so I don't know if it would be worth the $300 he wants for it.
I am not sure which bellows is bad, I think the U-joint bellows. With the drive lifted all the way up you can crouch down and look up into the space between that and the boat and see the bellows. It is about 4 inches around, and very dry and cracked. That is why the hole is in it, it just wore out. I never thought too ask him if the drive oil had water intrusion.
I will tell him to find another prop to put on it for a test run.
I just could not believe the drive would be that bad, it started and ran good, shifted smooth, and the drive ran very quiet. He shut it off when it was still in gear with the prop spinning, and of course the prop clicked as it wound down to a stop. It made the ratcheting clicking sound as it stopped spinning, which in his mind confirmed the drive was bad.
I am also wondering if he did not understand what the mechanic was telling him. He said it needed new U-joints, new bellows, and what he thought was the drive, all for $1700. That sounds cheap for all that work.
I think I will tell him to get a second opinion from another mechanic.

Thanks again for the replies, you have been a big help.

 

[Bt Doctur]

Re: Mercruiser drive or prop?????

unless it was run low on oil

 

[water_rat03]

Re: Mercruiser drive or prop?????

unless it was run low on oil

Did it grind and make noise, or did it run smooth and quiet? That is what stumps me about the bad drive gears diagnosis, it run like usual, quiet no grinding noises but ran slow. Normal engine RPM but low speed.