2002 Merc Mag MPI Overheats

[BillyZ]

I have a 2002 Tige 22v that has decided to overheat. I have replaced the thermostat, the impeller, checked water flow before and after the oil cooler and everything seems to be working fine. When I run it on a fake a lake in my driveway at a bit of an angle (back end up), the temp gauge goes to about 110 and doesn't move much even if I increase the RPM's. I take it to the lake and run it and the temp goes to 190, 200 after 5 minutes give or take. I can almost rest my hand on the heads and am wondering if maybe there is a sensor issue. The RPM gauge has also stopped working this year, not sure if there would be a correlation but thought I would mention it.

Has anyone seen this before?

Thank you in advance for any help!

Bill

 

[Franzel311]

Get a thermometer gun from Homedepot there like $50 that way u can check actuall temp compared to ur gauges if u think there faulty..I just had a problem like this with my uncle's boat its an Sr272 Thunderbird with twin 350 mags the port engine was overheating in lake under load only ran fine on hose in driveway we replaced everything from the drive to the exhaust except the thermostat housings finally before we droped it off at the mechanic just for fun I switched the housings from port to starboard and the issue followed the housing and the engine that was overheating was cold as can be we had took them off previously when we changed the stats reamed them out and inspected them properly but musta missed something Cuz now with new housings both motors don't go over 150deg ever...hope that helps

 

[alldodge]

Howdy

You can put a piece of clear hose inline between pump and thermostat housing. If you see bubbles ya might be sucking air. Could also have a clogging of the inlet port from the bravo drive. Getting an IR temp gun will help

 

[thumpar]

Since it is a Tige and you are using a fake a lake it sounds like this is a true inboard so you don't need to worry about the drive. When on the hose you are pushing water in. On the lake the pump has to do all the work on its own. I would test the flow on the water.

 

[BillyZ]

Took to the ramp today. Pulled all of the hoses I could get to easily one at a time, started boat for a second and seemed to have good flow everywhere. Got it all back together and ran it at a fast idle for 10 to 15 minutes before it ran up to 190 and I shut it off. I have a buddy with a temp gun I will try tomorrow. In the meantime I am going to pull the thermostat housing and see if there is anything obvious.

Any feedback would be appreciated.

Thanks!

Bill

 

[alldodge]

Pulling hoses and watching water flow is not telling you much. If your pushing water against a restriction it won't show up without being connected.

As before, you need to know IF it is overheating, or is it just the sensor. If you don't want to buy an IR temp gun, or cannot find one to use, then use your fingers. Start the motor, and put your fingers on the thermostat housing, it should heat their first.

Have you pulled the hose off between the pump to the oil cooler? The hose end you want to remove is on the inlet side going into the cooler. Need to feel around in there and see if there are any impeller pieces.

Need to back flush every hose, starting with the transom and work your way around to the thermostat housing. If nothing is found, you need to continue thru the rest of the hoses