2001 2100v (350 MAG/MPI) overheating/thermostat issue....

[h2osk8er00]

You might double check the Tsat. That sure looks like it might be sticking or a slightly higher temp version vs the original 165. You can either replace it or if you can put it in a pot on the stove. Heat it up and check the water temp at which it opens up. As quickly as it’s bouncing temp I’d say your getting good flow now.

Copy that. Cheap part to replace even with OEM. Pretty sure I bought Quicksilver last time. Have to check my amazon. The weird thing though is that I replaced it due to this same symptom about 2 years ago but it continues to do it. I will wanna check it out though.

I was thinking I might look into the heater core too... I put a union piece there 6 years ago to bypass the core as it corroded from my years back east. Just wanna make sure nothing is blocking flow there.

Any other suggestions please advise! Is there a chance my manifolds are having an issue? Can they be cleared or inspected to ensure no blockage exists? Thanks Ruger!


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[Ruger761]

You can ceck flow by pulling you blue drain plugs on the sides of the block and in the manifolds. Only check them 1 at a time and compare side to side. Be careful as that water will be coming out really hot. They should be pretty equal in the same locations side to side, well assuming the drain port itself isn’t corroded or block a little.

[NICKYPOO]

That salt begins to solidify at 170*. I’d be willing to bet the exhaust manifolds have a ton of build up in them. That’s why your temp gauge is jumping around. It runs out of water to measure. No water at the sensor means no reading. There’s probably just barely enough water getting through the system to keep the motor from burning down.

[oldwakedoc]

Responding late to this thread but did you find the problem yet?

[h2osk8er00]

You can ceck flow by pulling you blue drain plugs on the sides of the block and in the manifolds. Only check them 1 at a time and compare side to side. Be careful as that water will be coming out really hot. They should be pretty equal in the same locations side to side, well assuming the drain port itself isn’t corroded or block a little.

Thanks for the information... I pull them regularly for the winter but never thought about pulling them intentionally and firing up the boat... Do I need the boat to get up to temp before I do such? Thinking this should be done on the trailer...

[h2osk8er00]

That salt begins to solidify at 170*. I’d be willing to bet the exhaust manifolds have a ton of build up in them. That’s why your temp gauge is jumping around. It runs out of water to measure. No water at the sensor means no reading. There’s probably just barely enough water getting through the system to keep the motor from burning down.

Well that is something new I did not know... However, I never had the boat go above 170* in salt water... this was the first time I had really ever experienced an overheating issue... Once I replaced the trans cooler and the impeller pulley, I didn't have any overheating happening.... I am going to check the flow through the manifolds by taking the plugs out though as Ruger761 indicated... I checked at the heater core near the helm and flow rate was good there... Also, water seems to pass through and out the exhaust on the hose just fine... But I know that underload the engine performs vastly different than on a trailer. Not sure if this holds true for water flow as well.

Thanks NickyPoo! This an expensive/difficult thing to replace? They seem readily accessible... Would a check of my flow from the drain plugs indicate anything? Or is it a lost cause? This boat was operated in salt water the first 11 years of its life... but since then it has only been on fresh water lakes. I have about 10 hours on it since the overheating concern and some of that was pulling wakeboards and I have yet to see a decrease in performance but I don't want to assume everything is fine... I may just be getting lucky...

[h2osk8er00]

Responding late to this thread but did you find the problem yet?

I have not... hopefully it is just a faulty gauge.. tried to put an additional gauge but the port i went to open broke when I tried to unscrew it with the 1/2 inch drive! Luckily it didn't move at all but I think a shop would have to use some special tool to get it out now...