Overheating M35-B

[epaolino]

I was wondering could a fouled prop cause overheating?

Took the boat out after an extended period at the dock to have a riser pipe installed. I felt the prop was fouled as we moved forward ( seemed sluggish ). Worked ok in low rpms. Plenty of water coming out of exhaust. warmed up and pushed past the no wake zone... in about a mile...over heating, blaksmoke and steam. I shut it down, check the antifreeze, ok checked oil, ok. let the engine cool a little, restarted water coming out exhaust, cooled down to normal. Kept it below 1500 limped back to the slip. Checked the raw water stariner, clear Ok, Checked Impeller, Ok no broken vanes.

Could it really be just a badly fouled prop?

[MarkSF]

Interesting, as mine behaved exactly the same yesterday. It was fine heading out at 2K rpm, but on the way back the temp started to rise until it hit 190. At that point I throttle back to 1400rpm and the temp dropped right down.

Haven't checked the strainer yet though.

But in answer to your question, I think it could cause overheating yes.

[epaolino]

Thanks for the reply mark....

I thought that a fouled prop would act like a "freewheeling" prop with no bite and would do no work.

[emoney]

I'm no expert, but I'd think a fouled prop might show other signs/symptoms as well??
What about the "cooling pump" (I may be misnaming this part) that's belt driven on the top-front of the engine? Is your drive belt tight enough? Just throwing out suggestions.

[epaolino]

The belt driven engine water ( antifreeze ) pump, checked belt tension and is not leaking. Raw water pump impeller is intact and ok.

[MacGyverRI]

It could have algae or barnacles on the through hull (usually a slotted intake) restricting the flow.

[eherlihy]

The answer to your question;

could a fouled prop cause overheating?

is YES.

Growth on the prop adds to the drag. Depending on how much growth, it could require SUBSTANTIALLY more torque to spin the prop at a given RPM. The prop could even be restricted by growth.

Think of it as if you were towing a heavy load with your car. The engine has to work much harder to accomplish the same amount of work.

[emoney]

Originally Posted by MacGyverRI

It could have algae or barnacles on the through hull (usually a slotted intake) restricting the flow.

^this, is a great thought. Very easy to check; grab a snorkel mask and jump in. Also, simple to solve too. Hopefully this is the case. I would suggest, however, that in the future you think about installing a temp gauge. By the time the "smoke billows", it can be way too late. Just a though. Good luck.

[epaolino]

Bottom kind of clean.... Prop loaded!

[epaolino]

I would suggest, however, that in the future you think about installing a temp gauge. By the time the "smoke billows", it can be way too late

Good Point.

Temp gauge is at ankle level....was hot enough to wiff some steam not hot enough to trigger hi temp alarm... I need to double check the alarm...