Mercruiser 5.0 efi-00 cooling problem.

[MattiasJansson]

Hey all!

I have a problem with a sea-ray 215 Mercruiser 5.0 efi engine.

When I run the boat the temperature goes up to operating temperature but drops to pretty much the bottom of the gauge, then it turns back up to operating temperature before dropping again, and so on. I have changed the thermostat and temperature sensor and checked the gauge but nothing helps.

Has anyone experienced this phenomenon and knows what can be done to fix the problem?

 

[dpb]

Is this in the water or on muffs?
At idle or whilst under way?

 

[MattiasJansson]

Is this in the water or on muffs?
At idle or whilst under way?

It Started in the water when I was driving, but have the same problem now with muffs on land, idle.

 

[dpb]

As you have changed the thermostat already I would check the sea water pump impeller and the tightness of hoses on the suction side.
I am thinking that the flow is lower than it should be with a blast of water coming through on a cycle.

 

[QBhoy]

I’d check that thermostat again. Don’t suppose you’ve put it in the wrong way or upside down ?