Sudden Loss of Thrust

I have a 83 Baja20ss with a 350cid Chevy and 260 Mercruiser and stainless steel prop. The motor is brand new. We were on the lake again today and all was going great but after like 30 minutes of boating we heard 2 slight noises, mabye like the prop may have tapped something, possibly, it wasn't real loud but me and my wife both noticed it. I slowed down and we went for a bit more but after like 4 minutes we slowed down and then when we went to give it full throttle again the motor reved up like normal but we could only go like 15mph or so max. The bow would go up but not enough power to plane out. Engine is running great, not overheating, no other strange noises, no other issues except for a loss of power now. The prop does have a nick on one of the blades which I think is new. Could that be causing this big of an issue, I can't even get over 20mph. The prop has slots that it slides on to so I don't think that could be slipping, could something else be slipping someplace. Any helpwould be appreciated! Thanks

 

You may have partially spun your prop hub. If you can turn the prop on the hub by hand with the engine off!!! and the out drive in reverse, (turn the prop forward - lol), that should tell you what's up. Be sure to wear gloves. Stainless props are very unforgiving on outdrives and hubs when it comes to impacts. Unless you race your boat it is really not worth difference in price or the marginal increase in performance.

 

Well it's not that.

Ok you weren't kiddin about wearing gloves!! I put it in reverse gear with the engine off and it would not turn even a little bit clockwise. Tried the same with it in forward gerar and it woulden't spin counter clokwise. So that seems ok. I know that is the way it has been all along. I'm fairly familiar with the inner working of the sterndrive but not sure what else could be going on. Like I mentioned the prop has a ding in it that wasn't there before, could that do this? The engine is running great and no strange noises.

 

The coupler.

The engine has a stainless splined shaft. The outdrive has a coupler that is aluminum. To replace it, you need to remove the engine. Normally, you only need to do this every other year. When you hit something, sometimes you need to do it then.

Its one of those wonderful things about I/O units.

Just a couple of boat units, and you'll be back in business. You know: Break Out Another Thousand. BOAT units.

 

Ok well I looked at the splined shaft and there was no shavings and the rubber looked good. So then I looked for a spun hub on the propeller. I can't say for sure if it spun but the rubber looks good. The prop looks pretty banged up on 2 of the blades so my awesome neighbor lended me a new stainless steel prop he had that was almost the same as mine and we took it out to the lake and I kid you not it took off like a rocket. No more problems. Ran it for a half hour start stop start stop, runs great. I'm not sure if it was a spun hub or the dented prop? But I'm happy it's running again!!! Thanks alot for the advise guys!

 

Your prop is spun, it's rare that you would be able to spin it by hand even if it is bad and there isn't anything else that would give symptoms like you described. Take it to most any marina or boating store and they will have it repaired to like new condition.