Engine runs hot...

[Duff]

I took the boat out this past weekend and something interesting happened... actually this is the 3rd time in a month. I'll be running about 4500 - 5000 rpm's and suddenly the hot light comes on and the motor cuts down to the safety zone under 3000... so I back down to idle and the motor is sputtering and wants to cut off. The water flow is strong - no problems there. So I idle along for awhile expecting it to cool down but it doesn't. I put it in neutral and within 15 seconds the hot light goes off and I see lots of bubbles coming up from around the prop. I then put in gear and off I go with no further issue. So I'm thinking that maybe I had some line wrapped around the prop making the engine work hard but I see no evidence of that whatsoever. That happened saturday and before that it happened twice while I was in the keys - same exact thing. But yesterday I ran all day long without any problems. I took it to my mechanic after the keys trip and they couldn't find anything wrong. Any thoughts?

[Jack Hexter]

Maybe picked up some grass around the intake. If/when it happens again, put it in reverse for a couple seconds This should clear the intake and help it cool down faster.

When was the last time you changed your impeller?

[Howard/Jax]

I think Jack may have the right answer. We always tell our customers that a water pressure gauge is better then a temp. gauge for determining water flow to the engine. Some times the sensor that sets off the light or buzzers is defective. But, then again we handle only good engines LOL:eek:

[Duff]

That's the odd part... it was peeing strong when this happened. I had full service done in april with an impeller replacement. I get that grass-clog once in awhile but usually the water flow stops when that happens.

[Mont]

Duff, for $30-$40 bux or so, you can buy one of those infrared point and shoot thermometers and see what the actual temps are. I chased down a stopped up vent line on mine rig by comparing temps when the guage showed normal and when it showed hot. Run it once and write down the temps and then when it shows hot, pop the cover again and see if it really is.

You might have something like some scale or an oyster loose in the block and when it gets in the right position, it blocks the flow. When you shut down, it moves and the problem goes away until the next time. That exact thing happened on my Dad's boat.

[Duff]

The thought did cross my mind about it being a false reading somehow, as the water coming out the pee-hole did not feel all that hot. I found one of those thermometers on Overstock... http://www.overstock.com/Auto-Parts/Infrared-Point-and-shoot-Digital-Thermometer/3572521/product.html

Where would I aim it - right on the motor block?

[Mont]

aim it right on the side of the engine block. Be sure to write down the temps when it's showing OK, so you can compare them to what's happening when it shows hot.