2002 320 Sundancer 320 Overheating 350 Mag MPI

[Aaronpav2001]

Good morning and Happy Easter all,
So I got the boat out on the water the other day after winter repairs and ran here easy for about 20 minutes at low RPMS between 2000-2500 and then ran her good between 3700 and 4000 RPMs for another 20-25 minutes. Boat initially ran and sounded great. Temps remained between 170 and 200 RPMs on both engines but were creeping up towards 200 degrees. When I got back to the dock the starboard engine alarm sounded indicating over heating. (yeah super frustrating). Both engines were pumping water well both at dock and under way. Checked coolant it was very low on starboard engine. Mechanic went through it and said there was not water in the engine??? I don't know what that means. He also added coolant as it was very low. I had the same issue when I pulled at end of season. We topped off coolant and water (again I don't know what that means) but it did correct the issue for a couple more trips.

In the off season I replaced plugs, caps, IAC valves, circulating water pumps, oil changes impellers both engines and generator and both shaft seals.

I went out yesterday for about a 40 minute ride. I had no issues but only ran her for about 5-10 mins at higher RPMS but I had no issues.

My next step was going to replace the thermostats as it seems easy and cheap and probably should have already been done. Does anyone have a part number for the kit? I see one ending in 5 and one ending in 3. Any other suggestions what to check? Tough to get under the boat and check in takes right now as water is freezing. Any suggestions would be great! Thanks all!

 

[superwa]

You may be leaking coolant somewhere? You added coolant at the end of the season and again at the beginning of this one? Maybe check the heat exchanger? May need to be cleaned or replaced. Also as the temp goes up do you still see water pumping or switches to mostly steam? That could be a sign that you need a new hose somewhere.

 

[Lazy Daze]

First thing... need some clarification as there seems to be a discrepency. Do you have fresh water cooled engines or raw water cooled engines? Do you have a heat exchanger and a coolant overflow bottle? The standard engines would have been raw water, while the optional "Horizon" engine would be closed cooled.

"Assuming" Horizon engines... The reason it didn't overheat yesterday was becasuse enough coolant hadn't yet leaked out.

You shouldn't be losing coolant and having to keep filling up. There's a leak somewhere. Based on what you said you personally replaced over the off season, it sounds like you're up to task of checking things out. First would be a very CLOSE visual inspection of everything. Next would be to remove the heat exchanger and inspect.

FYI... the time to get this fixed would have been in the off season... you may run into a big wait time at this time of year. I know, hindshight is 20/20

 

[Aaronpav2001]

The boat is raw water cooled and seems to be pumping consistent water on both engines. I'm sure you guys can tell I am no mechanic. The boat has the two containers for antifreeze above both engines. Hoses have been inspected with no leaks and minimal antifreeze in bilge.

Is it worth replacing thermostats?

 

[Lazy Daze]

OK, I think I see where the confusion is - you're confusing certain terms.

Raw water cooled means "raw" water (whatever you're sitting in) goes through the engine. Closed cooling means there's AF in the engine and the AF is cooled by raw water. If your mechanic added coolant and you have two containers for AF, you have closed cooling engines.

No, t-stats won't solve the issue. There's a leak. There should be ZERO AF in the bilge. In light of your Post #4, best bet is to just have your mechanic do his thing.

 

[Aaronpav2001]

You are correct. It is closed cooling. I was confused.

 

[Aaronpav2001]

Also manifolds risers etc were all replaced in 2015. Moved the boat to fresh water ever since.

Praying this is not the issue

 

[Aaronpav2001]

Looks like it was just a leaky valve. Replaced and appear to be good to go. Thanks for the help all.