Am I way over propped?

[MNfuncpl]

Ok. I have a Baretta 17'3" supersport with the Volvo aq131a and the 275 od. The prop is a 14x19L. In the driveway with the muffs on it will turn 4500 rpm easy,with no heat issues. I ran it for 30 minutes at 3500 rpm and it hit 195f. In the lake it gets 3200 rpm wot and builds heat, slow it down and the heat goes away.What prop should be on this boat? Thanks.

 

[skydiveD30571]

Re: Am I way over propped?

Hitting 195 degrees is definitely a heat issue in or out of the water. You should never run the engine out of the water at 3500rpm.
The prop isn't the problem here. You have some sort of cooling problem.

 

[Don S]

Re: Am I way over propped?

When was the last time the impeller was replaced? Should be a yearly maintenance item.
Running an engine fast with no load is a non test and tells you nothing.
Even over propped you should get that hot at 3200 rpm.
Might also look at the hose connection where the cooling water hose hooks to the outdrive. It tends to corrode and go away. On muffs and low rpm it doesn't hurt anything, but at higher speeds when it's out of the water and under load, it sucks air and lets the engine overheat.
That is a few of the more common things. Then there is a defective thermostat, heat exchanger dirty and plugged up. Other suction side cooling leaks and .................

 

[Eddie Ray]

Re: Am I way over propped?

Wow,I can't believe you ran the boat out of the water at that RPM for so long. Hope everything is okay?
No blood , no foul. I guess.

 

[MNfuncpl]

Re: Am I way over propped?

Thanks for the reply Don. I have replaced the impeller and back flushed the heat exchanger.It is not plugged. I did hook up my garden hose directly to the pipe inside the boat and check for leaks at the lower unit and found nothing. I taped up the intake holes and the drain hole and tried to pressurize the system and see no water leaking where it shouldnt. The boat runs nice and no heat issues on the garden hose. 4500 rpms is no problem. In the water 3200rpm is a struggle and it gets hot. It sounds like it is working way too hard for this speed.It stays cool at slower speeds. What prop is common for this size boat with this set-up.

 

[MNfuncpl]

Re: Am I way over propped?

Hi Eddie. Thanks for the concern, but as I told don, I have cold water blasting thru the motor and out the exhaust ten feet behind the boat and the temp gauge never gets close to a point where I would feel uncomfortable about running it. 4000 under a load is a normal number for this motor,so 3000 with no load should not be a problem. I dont recommend doing this for fun, I am just testing to see if it is a heat issue or a load issue. I just think it may be over propped. What prop are you running on yours. Thanks.

 

[Don S]

Re: Am I way over propped?

Since everything engine wise is ok, I will move this over to the prop forum.