Problem caused from hitting a rock with prop?

[ThomW]

Hello all. I have a 2001, 25' tritoon with a 1987 BlackMax 200hp Merc on the back. The motor was running great and would push the pontoon along at a good clip. The other day I hit a rock and tore up the aluminum prop pretty good. I limped it back to shore, and put on a replacement prop. Same pitch and diameter. The prop shaft does not seem to be bent at all, and was not shaking the boat at all. The issue is that now the motor won't idle (unless I adjust the idle screw to a higher RPM which affects smooth shifting) and wont go over 3000 rpm's under load. In neutral it will rev up fine. What could I have done by hitting the rock that would cause this issue? Please, any and all help is appreciated!

 

[flyingscott]

If your motor has a flywheel key check that could be bent

 

[ThomW]

Not sure what you mean by a flywheel key. Where in relation to the flywheel would that be? I'm not aware of the flywheel having any "key".

 

[flyingscott]

What is the serial # of your motor. Look down at the flywheel and see if there is a slot where it sits on the crank shaft. The flywheel key keeps the motor in time, if you hit something they can bend and cause the problems you are having.

 

[ThomW]

The serial number is B211163. I will look at the flywheel tonight an see if I see one. I'm looking at the parts diagram for the motor and do not see a pin on the flywheel or the crankshaft diagrams...but that doesn't mean it doesn't have one.

 

[flyingscott]

Your flywheel looks splined no key and I don't remember if they have a hub or how that works been a while since I have seen one. Somebody will be along with more knowledge on that then me.

 

[ThomW]

Thanks for trying! I hope it is something simple and not going to be a huge repair. Just seems strange that hitting the prop would affect the idle and cut RPM's to 3000. I wasn't going that fast when I hit the rock either. I know the timing could affect the idle, but would that also cut RPM's off at 3000? Fingers crossed that someone here has an idea of what could have possibly happened.

 

[jimmbo]

Does the prop shaft spin smoothly and easily in neutral? The impact may have distorted the gearcase and pinched, or shifted the bearing carrier out of alignment

You did make sure that the thrust hub either stayed on the propshaft or was transferred to the new prop?

 

[ThomW]

Yes. The prop shaft spins very easy and smooth in neutral. I also looked down the shaft while spinning it to see if it was bent at all, seemed straight as could be. There is also no shaking or vibration that would indicate a bent shaft (well no more shaking than is to be expected from a 1987 200hp 2-stroke!)...

I also did make sure the thrust hub was transferred with the new prop. I did notice, however, that there was a bit of water on the prop shaft splines when I took the old prop off. I could tell because of the spline grease that was on the shaft, it was milky like water was getting onto the shaft splines. Any thoughts on that?