Boat guys - Overheating problem
 

I have a 31' boat with twin 7.4 liter Mercs. The port side motor runs significantly hotter than the SB side. 160 deg VS 190. at a constant 3100 RPM

I have recently done the following:

cleaned out the intakes (they were pretty gummed up - engine ran 205 degrees prior to cleaning)
new impellers
cleaned risers
checked thermostat

Not sure what to do next.

Here is a picture of the old girl.

http://forums.pelicanparts.com/uploa...1245881303.jpg

I/O drives? counter rotation?
equal water flow out? [I bet not !!]
you did reverse the impeller on the non-standard motor?
remember if it runs backwards the pump needs to run backwards too

Thanks for the reply.

Boat has I/O with counter rotating props.

I guess I would have to check the water outflow with the boat out of the water?
Not sure about the reversing the impeller... I'll check on this.

I dont know power boat engines, I'll ok with sailboat engines. Have you flushed the block? Vinegar does wonders.

Also, any chance the hot engine is lean? Clogged jet/injector?

Co-incidently one of the carbs was rebuilt recently - I'll check with the mechanic.

I know a guy that tried to run a car carb on his boat. Even with the fattest jets it melted the pistons. Make sure it's setup right.

Check the sensors too - they are famous for being off on the mercruisers. That said - I'd check mixtures first. Sea Ray?

Impellers are just those rubber-vane guys, right? No right or left when new..
So Bravo3 drives?
Didn't say where you play, lotsa sand?
I/O's are sand vacuums. Pretty easy to pack a motor full...
Pull some of the block and manifold drain plugs and poke a screwdriver up there, any exhaust restrictions?

The mechanic is going to look at the mixture today. Not sure where the sensors are but I'll ask him about these too. The boat is a Formula.

Impellers are indeed those rubber vaned deals. No sand where I am.

Thanks again.

Sensors are on the thermostat housings - at least they are on the 5.7's, I'd also pull your hoses - as I had one that put on that was an auto 1" hose that had partially collapsed - and gave me about the same temp difference.

How about heat exchangers? When were they replaced? or cleaned? You can get them cleaned at a radiator shop - you can also run white vinegar through them that will remove some of the scale. I'd get em cleaned or replaced if they haven't been lately (last 5 years)

Nice looking boat.