Prop Just Stopped Spinning Under Power

njesqs

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Jun 16, 2011
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I have a 1991 Galxie Walkaround with a Mercruiser 4.3 V6 Alpha One Inboard Outboard, my first I/O ever. I know little about this boat as the man I purchased it from had little to no knowledge of boats.

I took my boat out today and after slowing down to cross over a large boat's wake, I throttled back up and ........ nothing! All that I heard was the engine reving but no forard momentum. I immediately shut off the engine to see if I had snagged something. I hadn't. I started the boat back up and put it into forward gear... no momentum but plenty of reving. I then tried reverse. Same result.

After getting the obligatory tow back home, I am stuck wondering what may have happened and whether or not my boat needs to be hauled out for repair. I am able to spin the prop both CW and CCW in neutral. I have also been able to spin the prop CW with the throttle engaged in forward (although it spins smoothly and then gets "stuck" and then spins smoothly) but not CCW in forward gear. I am able to spin the prop both CW and CCW in reverse. I have observed the clutch cable move the clutch mechanism located at the top of the engine. But even though the clutch cable moves the mechanism, there is no engagement of the gears and no movement on the prop.

First and foremost, what are the possible mechanical issues which may have caused this particular set of facts. Secondly, does the boat need to be hauled to fix the possible mechanical problems, and lastly, while I am somewhat mechanically inclinded and wouldn't mind fixing this myself, are the necessary fixes difficult or require the engine to be lifted or anything else that may be well above my level of comfort/skill level.

Thanks
 

JWebber

Petty Officer 2nd Class
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Oct 21, 2008
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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

Pull off prop and see if your hub is spun. I would start there!
 

Don S

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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

It could be nothing more than a spun hub on your prop. Depending on the type hub in the prop, it may or may not move the boat at 700 to 800 rpm.
Did the engine temp ever go up? Did you smell rubber burning per chance?
 

Fordiesel69

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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

Did you just slow, or shift into neutral to cross the wake?

If you went to neutral and then back to FWD and nothing, you have a cable / drive issue.

A spun engine coupler will produce a burnt rubber small, a spun prop hub will make it so spining the prop by hand will be easy.
 

aspeck

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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

Another vote for the spun prop hub.
 

njesqs

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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

Thank you for all of your input. At this point it appears the concensus is that I spun my prop hub. A problem which may require me to pull the boat out temporarily and not lay it up for a major repair. I hope you are all correct. As to the circumstances of the incudent, I did not put the boat into neutral, i just slowed it. I did not smell a burning rubber odor although I will admit that the wind was blowing front to back at at 15-20 so I might not have smelled it. As for the temperature, it was operating in the normal range before this happened and I only turned the engine on for a few brief moments to see if the gears would engage and then kept them off thereafter. The only thing that has me concerned is that when the engine is on and I move the throttle from neutral to forward and/or reverse, I do not hear the gears engaging (making that customary grinding clucking noise). Any thoughts on my circumstances thaking the gear issue into account?
 

Utahboatnut

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Messages
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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

I would start with the prop and move from there if that is not the issue, if you are careful you can remove the prop in the water. Make sure you take off the thrust washer once the prop is off just so it cant get washed off by a wave or current. Have a good look at the hub and splined section(depends on your perticular prop) or have it checked out by someone. If thats not it then yes its time to pull the boat out of the water and start eliminating possible issues further down the chain from the prop. Hope it is just a spun prop...
 

Don S

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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

Look behind the engine at the back of the coupler where the splined shaft from the outdrive goes in. Do you see a lot of metal shavings?
 

njesqs

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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

I looked behind the engine toward the transom. I did not see any metal shavings anywhere including near the shaft which extends out of the engine, through the tansom into the outdrive.
 

04fxdwgi

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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

I looked behind the engine toward the transom. I did not see any metal shavings anywhere including near the shaft which extends out of the engine, through the tansom into the outdrive.

If you busted the drive train between the engine and drive, you would have lost the water pump on an Alpha and the engine would have overheated, post haste, with no water pump. Sounds like the hub, because you never shifted out of gear and it failed.
 

njesqs

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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

Ok so I have been in the water this morning trying to get the prop off the shaft. I was able to unscrew the prop nut and lock washer without putting the boat into gear (I held the prop while turning the nut with a wretch). But I have been unable to get the prop off the shaft. Does the fact that I was able to get the prop nut off without putting the boat in gear change the possible diagnosis. Any suggestions on how to get the prop off of the shaft now?
 

Doernuth

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Re: Damn Prop Just Stopped Spinning Under Power

Re: Damn Prop Just Stopped Spinning Under Power

Tap it with a rubber mallet? The prop should be held on by the washer with the little bendy tabs not the nut. The fact that you could turn it without engaging the gears is just fine.

Do you know if your prop has a removable hub or if it is integral?
 

njesqs

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Re: Prop Just Stopped Spinning Under Power

Ok so the latest developments are that I could not get the prop off while it was in the water. Had the boat hauled and only was able to get the rpop off using a five or seven pound sledge hammer (short shaft). The prop hub was not spun and looked in very good condition. The marina I took it to had me start the engine and asked if the shaft running from the engine through the transom was spinning when it the engine was on. It wasnt. It looks like it is a bad engine coupler. The chief mechanic belives that when I crossed the wake it broke the engine mounts allowing the engine to move and the couple and shaft to become misalligned, causing the problem. I'll keep everyone posted for informational purposes and thank everyone for their help and ideas.
 

HT32BSX115

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Dec 8, 2005
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10,083
Re: Prop Just Stopped Spinning Under Power

The chief mechanic belives that when I crossed the wake it broke the engine mounts allowing the engine to move and the couple and shaft to become misalligned, causing the problem.
Yeah....possibly. But it didn't (the broken engine mounts and subsequent mis-alignment) happen right then. This has probably been brewing for quite some time.

Either way, you'll be removing the drive and engine(in that order) to replace the coupler...... That's a fairly simple job. R&R engine and drive

"Fixing" possible rotten stringers and/or rotten transom...........that might take a little "longer"


Sorry about that!


Rick
 

Wes M.

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Jun 11, 2011
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Re: Prop Just Stopped Spinning Under Power

I just bought a coupler for my 3.0 Mercruiser and the part cost $200.00 at Iboats.com. The outdrive and motor was fairly simple to pull but making the repair on what caused the mechanical failure is going to take me a while. I found some rotten wood that supports my motor mounts that has to be replaced.
 

njesqs

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Jun 16, 2011
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Re: Prop Just Stopped Spinning Under Power

Ok so I went to the marina yesterday and spoke to the chief mechanic. We went over to my boat and spoke with the tech working on it. What they found was almost exactly what he predicted. The engine had shifted and caused the engine coupler to strip. The problem was not because of broken engine mounts, nor rotten stringers. Rather the problem was caused by some one using steel bolts to hold down the engine in their mounts. Those bolts were severely rusted and pulled out of the stringers or otherwise failed. Unfortunately they had to replace the engine mounts which they could not get the frozen bolts out of. However, new engine mounts, new stainless steel bolts and a new engine coupler, gasket and I will be ready to go this week-end. I am impressed with the chief mechanic's knowledge, his and his staff's work ethic and the ability to do the work at the quoted price (although it was minimally more expensive due to the addition of the extra unforseen parts, larger stainless steel screws and new engine mounts, etc). If anyone needs repair on or around the Barnegat Bay in New Jersey, I would highly recommend Jims Mobile Marine Service at Townsend Marina, Forked River. Eventhough I was not someone renting a slip from his marina, he treated me and my boat with courtesy, professionalism and honesty.
 
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