Mercruiser 5.0 Overheating problem.

[ronaca88]

Hello guys. I need some help here.

I have a 2014 Mercruiser 5.0 MPI with Alpha 1 Gen II with no more than 150 hours. I was taking a ride las weekend and everything was normal. We did some wakboarding, cruising and then we anchored at the bay. Couple of hours later, when we want to return to the dock, the engine starts overheating at idle. We had to be pulled to the dock.

First clue was that the impeller need to be changed so I order one and I installed yesterday, bad luck, it stills overheating. I'm thinking about change the thermostat, but is there anything I can do to verify that the thermostat actually needs to be replaced?

​Any more ideas what I should look at?

I appreciate your help in advanced.

 

[indybleck]

Take your thermostat out and put it in a pan of water on the stove, heat the water up and use a baking thermometer to see the temp of the water. If it is working right it should open around 140*-160* depends on what thermostat you have.

 

[Fun Times]

How bad was the old impeller? Was there missing blades that may have flowed upstream causing a blockage somewhere? If so, then back flushing may help dislodge any old parts.

Being 2014, Does your engine have Mercruiser's catalyst exhaust system as they have a different type/style thermostat housing.

Is your engine serial number handy?

 

[ronaca88]

Negative, the old impeller was right, no visible wear, nevertheless i change it. The serial number of my engine is 2A189803.

how I do the backflush proccedure?

 

[camalot]

Is it really overheating,or are the alarms going off and the gauge showing your over heating. A bad ground will do that! For the cost of them get a infra heat measuring gun and see what the temp of the engine and manifolds really are.

 

[nateo]

Heres a simple to do test that doesnt cost anything. Wish i would have started with this as i wasted hours troubleshooting overheat problem. Move sgifter into foward gear and spin prop counter clockwise. Make sure it locks. If it keeps spinning forever it could be a bad coupler. Start with bevause it only takes a minute. If it locks then remove your water inlet house from engine and run it on mufs. Thus will tell you if its something with drive or engine.

 

[keith2k455]

Please note, never touch the prop with engine running. Test while engine off!

 

[Fun Times]

Negative, the old impeller was right, no visible wear, nevertheless i change it. The serial number of my engine is 2A189803.

how I do the backflush proccedure?

Your engine model is a 5.0MPI A EC 2R 5.0L ALPHA MPI. Emissions Control/Catalyst Exhaust.

You also have a new designed thermostat housing that utilizes a poppet valve which may also cause an heat issue should it fail...So inspect that as well. http://www.mercruiserparts.com/Show...desc=Thermostat+and+Housing,+Standard+Cooling

Your cooling system won't be as easy to back flush like some of the other model engines. Guessing you can try finding the inlet hose 'item number 30 at the T/housing and see if water comes out the drive. But since you have a check valve (item 2) it may not work.
http://www.mercruiserparts.com/Show...ling+System+(Alpha),+Single+and+7+Point+Drain

Does your engine have the flushing attachment device on the inside of the boat so you can flush the engine with the engine turned off? < If so, don't run the engine or you'll burn the impeller in the drive.

Does water flow out the exhaust relief holes near the transom?

 

[ronaca88]

PROBLEM SOLVED.

I change the thermostat for a new one and it seems that that was the problem. No more overheating and temperature was stabilized on 175 F.

It seems that the thermostat has to be change YEARLY when running the boat on salt water.

Thanks for your help guys.

Best regards.

 

[nickmo]

Glad your problem is solved, but I never heard of a thermostat having to be changed yearly. I have a 2008 5.0 RWC in salt water. It doesn't have the new design like yours, but I haven't changed the stat yet. Maybe I'm on borrowed time. Anyway glad your ok.