Mercruser 190 HP 4.3 Getting Hot

[kcwaterbug]

I have a 2001 Stingray with a Mercruser 190 HP 4.3 that is running around 180-190 degrees with a 160 degree thermostat. The other thing I noticed is that the port exhaust manifold is cool to the touch and the Starboard Manifold is so hot you can't hold your hand on it for more than a second. The boat has 58 hours on it, has only been run in freshwater and I replaced the raw water impeller a little over a year ago when the boat only had 30 hours on it. I am wondering if I could have a blockage issue but I am not sure where I need to start inspecting. Any help would be very appreciated!!

 

[HT32BSX115]

Re: Mercruser 190 HP 4.3 Getting Hot

Howdy,


You probably need to look through the raw water circuit and determine where the restriction is.

Those little white "balls" below, help to regulate and equalize the cooling-water flow to each side.

Hot risers are sometimes due to blockage them from rust or or other debris in the t-stat housing....... (impeller fragments etc ) .........or sometimes the "balls" get stuck or are partially blocked with debris/impeller fragments and cooling water goes to the side with the least amount of blockage.


If there's enough blockage so as to restrict total flow, the engine will also get hotter than it should.


regards,


Rick

 

[Brentathon]

Re: Mercruser 190 HP 4.3 Getting Hot

I just determined that my new Sierra brand impeller was causing my high-rpm overheating issue.

 

[NHGuy]

Re: Mercruser 190 HP 4.3 Getting Hot

Definitely get the hoses off and check for debris! You can check for stuck exhaust flappers or flapper parts in the down pipe too. Also, has it run at the correct temp this year? If not maybe you had a freeze issue that has gone undetected til now.

 

[kcwaterbug]

Re: Mercruser 190 HP 4.3 Getting Hot

I have not noticed it being hot before the last time I took it out and the boat has always being store inside in a heated garage. I guess I will start pulling off hoses and do some inspecting. Will I need to replace gaskets if I remove the thermostat housing? and should I go ahead and replace the thermostat while it is torn apart?

 

[HT32BSX115]

Re: Mercruser 190 HP 4.3 Getting Hot

Will I need to replace gaskets if I remove the thermostat housing? and should I go ahead and replace the thermostat while it is torn apart?

You should get new gaskets if you remove the housing.

When you replaced the impeller before was it intact or was it disintegrated? If it was or pieces were missing, you NEED to find all of them. Those pieces will go downstream and restrict total flow and cause overheats or a hot riser.

loss of water flow to one side will cook (burn/destroy) all the rubber parts in the exhaust system on that side...... (including the shutters)

 

[kcwaterbug]

Re: Mercruser 190 HP 4.3 Getting Hot

When I replaced the impeller it looked fine but I knew that it was 8 years old and I didn't feel comfortable with that.