Alpha One, Prop doesn't spin - Any ideas?

[tmh]

I'll be taking my boat to a mechanic for this one, so I'm not looking for anyone here to magically solve my problem.......but I'd like to have some conversational knowledge of the potential issues when I talk to him.

1985 Mercruiser Alpha One recently repowered fro 305 to 350 engine. Out on Monday doing a short WOT run to test new prop had it about 4600 rpm, 48 mph and I was tapping the trim out a little to max out speed (my trim limit is inoperable so i can't be sure i didn't go too far). Anyways, the prop stops and I shut it down fast. When I re-start, the engine sounds fine, but just revs when I try to go into forward, no boat movement at all. When I try reverse same thing except the engine stalls also. So I get towed in.

I tried to move the prop by hand when in gear and it only moves one way with quite a bit of my weight on it, so I assume not a spun prop. I have read here that a misaligned engine install could quickly ruin the coupler so I'm wondering if the guy who installed my 350 engine messed up. he said the engine mounts were very sturdy and the bolts caught fine so I don't think I have mount rot issues (unless he missed it).

The marina guy (not the mechanic) said likely a coupler issue or the gears are fried. Seems reasonable to me. I don't have the boat here so i can't check anything right now but I might tomorrow.

Any other thoughts on what may have happened?

 

[Bondo]

Re: Alpha One, Prop doesn't spin - Any ideas?

Ayuh,....

Looking down behind in back of the Motor,....
The Driveshaft can be observed,...
If the Coupler is Stripped,.... It Won't Turn......
It motor will Overheat with a Blown Coupler......

After That,....
It could be the Upper, or Lower drive.....
Checking it's Oil will usually give you an Idea on that 1...

 

[DayCruiser]

Re: Alpha One, Prop doesn't spin - Any ideas?

I have found that what you learn here really helps when talking to a mechanic about your problem. So its a good idea learn all you can here before going to a mechanic--imo

 

[tmh]

Re: Alpha One, Prop doesn't spin - Any ideas?

Ayuh,....

Looking down behind in back of the Motor,....
The Driveshaft can be observed,...
If the Coupler is Stripped,.... It Won't Turn......

OK, I'll have a look maybe before I go to the mechanic with it. I guess I'd have to start it and put it in gear to do see it move, right?

 

[ziggy]

Re: Alpha One, Prop doesn't spin - Any ideas?

since ya just changed props. ya might put the old one back on just to be sure it aint the prop. or paint a line on the hub and the prop and splash it and see if the lines are still lined up after trying to motivate it....
could be bondos right too.... but i'd double check the prop just to be sure......

 

[BoatinFool]

Re: Alpha One, Prop doesn't spin - Any ideas?

I tried to move the prop by hand when in gear and it only moves one]way with quite a bit of my weight on it

Do you mean it won't free spin in one direction? If so sounds like lower problems. The dog clutches on an Alpha should let the prop free spin in the direction that it's in gear even if the upper or engine was locked up. For example, in FWD, the prop should free spin in the FWD direction but be locked up if you try to spin it backwards due to the gear dogs being engaged to drive it in the FWD direction. Opposite situation applies in REVERSE gear.

 

[tmh]

Re: Alpha One, Prop doesn't spin - Any ideas?

Yes, when in gear it does free spin one way and not the other, just like it always did.

Anyways, just got back from the mechanic and he knew it was the upper gears even before he finished getting the cover off the unit - it had that burnt oil/metal smell like crazy! So the gears are fried.....he'll be taking the upper and lower units apart to see if he can clean it all out or not.

He explained the various options and possible things he may run into, darn those gears or units are expensive!!! he's a great guy and was recommended to me, so I assume he'll do the job well and not rip me off. He may need to get an after market upper unit as he says it can be cheaper than the gear sets with labor to re-seal, etc.

Looking at Sterndrive Enineering's web site it looks like I could buy the whole drive for $1,195 but I don't want to install it myself so any savings would be lost. The upper unit is $595 or so. I hope this is what the mechanic uses for after-market parts as it seems like a good deal.

 

[tmh]

Re: Alpha One, Prop doesn't spin - Any ideas?

Well, the mechanic has the drive apart and he's trying to clean out the lower unit, says the upper is done for so definately need a new upper. He thinks the lube oil leaked out at the pro shaft seal....says no oil in the bellows so it didn't come out the top. Is this a common failure point? Also, what could I have done to prevent it? i did have the drive oil changed at the end of last season so I thought I did what I was supposed to. The boat is in a slip so I never saw an oil leak or drips.

He told me mercruiser now has a device that basically stores some drive oil (thru transom) that can go into the drive via some tube. The oil storage container is on the inside and has some alarm when it gets low. I think he said it's on new units and can be retrofit for older ones. Is this something worth the $$$ to have done? (Of course, as i spend $1K to fix the problem caused by oil leakage it seems worth it to me!).

 

[chiefalen]

Re: Alpha One, Prop doesn't spin - Any ideas?

before u drop it in the water every year u can have it leak tested that way if theres a leak detected u can have it resealed.

 

[brunolund]

Re: Alpha One, Prop doesn't spin - Any ideas?

are you sure it was refilled properly after being changed???

 

[tmh]

Re: Alpha One, Prop doesn't spin - Any ideas?

are you sure it was refilled properly after being changed???

Well, I had the engine changed but I'm not sure the mechanic did anything with the outdrive oil. For all I know my drive oil is sitting on his shop floor! Crap, I should have had it checked before putting the boat in it's slip.

I don't have the inclination to try to find specific blame on why this happened. Truth is, I used a rookie mechanic for the engine swap to save some $$$ and because I liked the kid. He may have screwed up, but he gave me an honest effort for reasonable cost. Yes, it's a lesson learned for me on penny wise/pound foolish, but that's part of life - especially boating life, as i'm finding out!

At this point, my old engine was ruined and now my outdrive, all since last season and all involving non-marina mechanics. What I want now is for my boat to work and work well - no more short cuts. Actually, I almost wish I had just ordered the complete drive from Sterndrive Engineering and had it installed for me. However, the mechanic working on it is very well respected locally and not looking to screw me so if he says new upper but the lower is OK I'll go along with that.