Guys please help me out.. I have NO THRUST in high rpm's and its not a spun prop

[captainstabin]

If anyone can offer some advice I would really appreciate it.
I have a 23' 1995 sea ray sundancer with a 5.0 merc/ alpha one second gen outdrive. stainless rapture prop
Problem: I have no thrust in higher rpm's and I am not able to get on plane

Possible reasons: 1) I keep the boat in the bay in wildwood without bottom paint, about 4 weeks of algae and barnacles grew on the bottom. Could this slow the boat down from 40 mph to 15? BTW I did pull it out and in the process of cleaning and bottom painting.

2) I also hit some fishing line that was tangled around the prop shaft. I removed prop and cut it out, the shaft seals looked fine without any oil leaking out.

3) Another possible reason is during mid tide near 15th st in north wildwood (needless to say how shallow and screwed up the channel is) I ran into some muc. I tilted the outdrive up a bit and pushed through only about 100ft.

After hitting the fishing line and also having the algae on bottom I was trying to get on plane by pushing the rpms up and the engine overheated. The buzzer came on and after a few boggs I was finally able to shut it off. I originally thought Something was preventing water to be sucked into the engine to cool it. After letting it cool down I removed the hose going to the thermostat and water was pumping through it so water pump is fine. I drove the boat back to my slip at about 1500 rpms, it seems to over heat only in high rpms.

The boat was running perfect about 3 weeks ago now all the sudden it won't move in high rpms?

Things it could be:
I took the prop to a specialist, he tested it said the hub inside prob is not spun. So it can't be the prop itself.
I heard theres a good possibility it could be the engine cupler. If engine is pushing 4000rpms and coupler is bad causing the cupler to slip then the engine will overheat because its not getting enough water to cool it, which had happened.
Or maybe it has something to do with the prop shaft?
Or could the outdrive need a rebuild?
What I will do first is clean and paint the bottom, put the prop back on and test it out.
If anyone has ever run into a problem like this can you please help me out with some advice.
Thank you

 

[kaz911]

yes - growth will do that for you... It will slow you to a crawl.

 

[techmitch]

First post so, Welcome aboard. My first test would be to measure the fresh water supply volume from the outdrive to the engine,

 

[1990-270-da-lover]

Hi and Welcome to CSR. I would bet that the trip through the mud could have sanded down your raw water pump impeller in the outdrive enough that the water volume being pumped to the engine is reduced enough that at higer rpm's the engine dosen't have enough cooling water pressure. Another relatively easy thing to replace before going deeper. Good Luck.

 

[Gary Hill]

If your boat is on a trailer, put the shifter in gear (keys off and out for safety!!!!!!!!!!!) and then try to spin the prop. you should hear and feel clicking in one direction and resistance in the other. In the direction of the resistance, try pushing harder, like with your foot. If your coupler is bad you will be able to spin the prop albeit slowly. Otherwise you would be spinning the engine which would be very difficult to do at the prop. If your bottom side is not too fouled up, like just a small amount of scum, it's probably not the issue based on your description.

 

[testlab]

Lots of growth on the hull will slow you down but it is growth on the prop that kills thrust. Since you're saying you've taken the prop to a specialist I guess it's clean so I think you've got a failed coupler.

 

[Half Fast]

When I did my impeller this spring the one I was replacing was completely shredded with just one of the rubber arm things left. But it was still pumping enough to cool the engine - although in my case it was low RPMs where I was noticing some overheating last fall. If you ran through the muck for even a short time you really want to change that, even if you get your thrust issues worked out.

As for that, I really think you need to get the hull, drive, and prop smooth before you start digging in to other causes.

 

[JimG]

I have spun a coupler and it was obvious... made a loud buzz and couldn't go anywhere. Check your exhaust boot... my brother couldn't get on plane and it turned out to be the boot. Normally the boot runs the exhaust through the drive and out the prop. With no boot or badly leaking boot the exhaust can cavitate the prop and make it ineffective.

 

[Bt Doctur]

check the oil in the drive