High RPM, heat and no acceleration in wet conditions

[sandysage]

Hello Everyone,

I am a brand new boat owner. 1989 Sea Ray with a Mercruiser 3.0 I/O. 870 hours on the engine. My boat has been in the water since late May. I have been using it frequently and it has been running fine.

Yesterday was about 60 degrees and rainy. I took it out. I was in canals and at a low speed (5mph) for quite a few hours. At the end of my trip I attempted to accelerate once I reached the lake. The engine got up to about 10 mph, the RPMs went way up but the speed of the boat would not increase. Over a short period of time the temperature went up to 220.

My plan was to take it to the mechanic tomorrow if I needed to.

Today it is warm and sunny. I wondered if the performance yesterday had something to do with the wet weather. I just took the boat out and it ran great! No acceleration problems, high RPMs or heat.

I want it to be able to perform in wet weather. Any ideas?

 

[mvoellinger]

Sounds like the engine coupler. If the coupler goes, the engine will "slip" and the u-joint won't spin, along with it the impeller, causing the engine to overheat.

Could also be the prop hub, but if its overheating, sounds like a coupler. Notice any burning rubber smell or anything?

 

[sandysage]

Update....

Just took the boat out again - beautiful conditions.

It ran great for about an hour but I started to feel the boat struggle and then the problems started up again. RPMS up to 4 but the boat only goes around 6 MPH. Sounds stuck. I tried to push through it but the engine just whined. The heat stayed normal today.

No, no smell of rubber.

Putting it on the trailer and taking it to the mechanic tomorrow.:smt089

 

[mvoellinger]

Update....

Just took the boat out again - beautiful conditions.

It ran great for about an hour but I started to feel the boat struggle and then the problems started up again. RPMS up to 4 but the boat only goes around 6 MPH. Sounds stuck. I tried to push through it but the engine just whined. The heat stayed normal today.

No, no smell of rubber.

Putting it on the trailer and taking it to the mechanic tomorrow.:smt089

If its not overheating this time, might just be a spun prop hub.

 

[Larry]

I would 2nd. the hub as the problem....

 

[sandysage]

Thanks for the ideas.

My boat has been at the mechanic and he just called to tell me that the problem is a bad anti siphon valve.

I hope this fixes the problem!