1990 Force 50 - Good power from engine but not being transferred to prop

[dwe]

I've got a 1990 Force 50 hp on a Bayliner Capri.
It was working great until I was fishing in the weeds for awhile.
On the way back from fishing, it didn't click in my brain :redface: to clean out the weeds so I probably rev'd it up pretty good while the weeds were wrapped around the prop and of course we didn't go very fast.

Came back home and took prop off and cleaned out all weeds. So I thought I'd figured out my problem. But the boat would still not go any faster than about 4-5 mph. The motor really revs up but the water just churns and the boat won't go any faster.

Then, I thought it was a prop issue so I took off prop and had someone notch it to see if it was slipping around the bushing. Went out and rev'd it up again and came back. Took off the prop and the notch lines still lined up. So that kind of ruled that out. Then I tried a different prop and the same thing happens. So it doesn't appear to be a prop issue.

Did I ruin something by running it with weeds wrapped around the prop or is that coincidence?

What else could it be?

Is there another place where slippage could be happening so the power from the motor isn't being transferred to the prop?

Can anyone help?

Thanks very much.

 

[jerryjerry05]

Re: 1990 Force 50 - Good power from engine but not being transferred to prop

Could be a broken shaft.Or the hub is spun,maybe the shear pin.
Turn it off.Put it in gear.Try turning the prop.It should make the flywheel turn.J

 

[dwe]

Re: 1990 Force 50 - Good power from engine but not being transferred to prop

Thanks for the reply!

I will try turning the prop tonight. I'm assuming I need to put it in gear first?
Will this test tell me if the shaft is broken?

As to the hub being spun, wasn't that what was tested by notching the inner and outer hubs on the prop to see if there was any slippage? The notches lined up perfectly as they were before I tested it again.
Or are you describing something else?

As to the shear pin, what should I look for? I'm assuming the shear pin is the one inside of the shaft that goes through the hole of the prop. That appeared to be fine but I have another spare one I can try but it looks the same as the one that's in there.
Thanks again.

 

[emoney]

Re: 1990 Force 50 - Good power from engine but not being transferred to prop

He could be talking about the shear pin that connects the lower unit
to the drive shaft. If you lower your lower unit by taking out 6 bolts
(two under snout, 4 holding the unit to mid section), the lower unit should
drop down and you can see where it connects to the drive shaft. There's
a shear pin holding them together with a cotter pin keeping it in
place. That could've broken and hence no true connection. If so,
it should be an easy fix. If you do this, make sure the water tube is
reseated when you put it back together. It's only a "lining it up" thing.
(Wow, how I've grown. To the point of giving good advice!)

Good luck and keep us informed.

 

[dwe]

Re: 1990 Force 50 - Good power from engine but not being transferred to prop

jerryjerry05:
I took your advice and spun the prop by hand and the flywheel does move. Does that tell me that the shaft is not broken?

emoney:
Is dropping the lower unit something that a novice could do? I'm pretty good at taking things apart, but sometimes getting boat motors back together has been a challenge for me. Do you know of a good diagram that might help?

I think I've pretty well ruled out a spun hub (unless I've got more than one problem going on here). I tried out a third prop which was brand new and still had problems. The performance was a little different, however it did not fix the problem. I can still tell something is slipping. At low RPMs, you can feel the motor wanting to catch. If I accelerate slowly, sometimes I can build up a pretty good speed (still I don't think it is top speed). Unfortunately, I broke off the sensor of my speedometer so I can't tell how fast I'm going.

I could sometimes notice an improvement if I shifted my weight (165 lbs) to the front of the boat. I also played around with the trim with no real noticeable change that was consistent. The one thing that was consistent however is that every time I punched it from a stop, the RPMs went up but the boat wouldn't go more than about 2 mph.

Can anyone give me any more tips or advice?
Anything is much appreciated.

 

[jerryjerry05]

Re: 1990 Force 50 - Good power from engine but not being transferred to prop

Go to boats.net Look this up.(Mercury Force Outboard Parts 50 H.P. (1990) 507F90D GEAR HOUSING Diagram)This will show what you have in the drive.
#24 clutch dog might have gone bad.Is it making any clunking or grinding?


Change the oil and see if there is any metal in the lower.Make sure you drain from the right hole.#27-28 Don't touch#29.
If 3 props are ok then something inside is wrong.

emoney??? The only pin is a water pump impeller retaining pin.There is no shearpin or other pins in that section.Post a pic of what your talking about.J

 

[Frank Acampora]

Re: 1990 Force 50 - Good power from engine but not being transferred to prop

Is the exhaust snout still there? Is it possible that the mass of weeds broke it off? A missing exhaust snout will let exhaust ventilate the prop, allowing the engine to rev, but little to no forward thrust will be delivered.

 

[dwe]

Re: 1990 Force 50 - Good power from engine but not being transferred to prop

Hey Frank,
You may have hit the nail on the head!
The exhaust snout is missing. Could that really break off due to weeds??
Interestingly, I also noticed that the plastic piece holding on my speedometer sensor is also broken. Possible they both broke at the same time? It's just curious how a metal piece could break off the motor. Maybe someone else had a Force 50 hp and needed the same piece so they "borrowed it" permanently.

In any case, since the exhaust snout is obsolete for this motor, I found a used one at the local boat salvage yard and will install it tomorrow. I am very optimistic that it will make a big difference. Thanks for the tip! I'll let you know how the water test goes.

 

[dwe]

Re: 1990 Force 50 - Good power from engine but not being transferred to prop

Oh, man (Frank), I can't say thank you enough.
The exhaust snout was the ticket!!
(imagine a choir singing "Hallelujah")

This entire summer has been wasted (for boating anyway) limping along with this boat and in and out of repair shops, paying highly trained "professionals" $110/hr to do nothing. Getting the kids all hyped to go knee-boarding or fishing just to have them be disappointed... AGAIN.

And now my two main motor problems have been fixed for free (except for a few parts) by the kindness of strangers. One was an auto mechanic at the lake where we were staying who found debris in my carburetor and a few loose hoses. The other was a missing exhaust snout which was pointed out to me on this forum here.

Many thanks to Frank Acampora who hit the nail on the head with his recommendation, as well as to jerryjerry05 and emoney who took the time to try and help. Keep on doing what you're doing because your time is greatly appreciated!!!