Interesting overheating problem?

[txduckman07]

On sunday, launched the boat and loaded everyone up. Idled around for a few minutes at the ramp to pick my wife up and got under way. Within about 5 minutes, the engine heated up to around 210. Not wanting to ruin everyone's day I said we should stop and swim for a minute. After that, we put a skier in the water and took off. Boat cooled to 180 and regulated flawlessly all day. Fast forward to monday...got on the water early. Got several sets in. Last pull of the day, look down boat has jumped very quickly up to about 220. Shut it down and limped it back in, temp gauge staying around 200-220.

Impeller was replaced at the end of last season. Thermostat was replaced less than a month ago. I will go ahead and change the impeller and see if that does anything. Does anyone know where the temp sensor is located on a carbed Indmar? Given that the temperature swings were sometimes erratic, may try pulling that out and cleaning or replacing it. Anybody had similar issues in the past?

Another piece of history on the boat, the original owners ran it in a river (one that can have a lot of debris at times). They installed a strainer to eliminate problems they were having. I've put about 20 hrs on the boat already, but is it possible there is some residual debris or buildup in the cooling system?

[myster]

You may have an impeller blade that broke off that is intermittantly causing your thermostat to malfunction. It happened to me the other way...ie thermostat stayed open and boat ran cooler than normal. You could easily check for debris from the water pump to thermostat!!:cool:

[papou]

I had an overheating problem boat would heat up on idle my new impeller would only last 40 hours caused by an air leak at the strainer if you see air bubbles in the strainer it's pulling air from some ware I also pressure tested from the through hull fitting to the trans cooler and found more leaks .
(It doesn't have to leak water to be sucking air)

[txduckman07]

UPDATE!

Tried one more thermostat. Seem to have good impeller flow as no water spilled from fake-a-lake (all came out of exhaust). Even ran it briefly with intake house off of thermostat housing and seemed to have good pressure. Ran it on a fake-a-lake for about 25 minutes. Warmed to 185 and stayed rock solid. Problem fixed....so I thought.

Fast forward to saturday. Took it to the lake early in the morning hoping to beat all the traffic. Launched and idled out of the no wake area. Temp climbed to about 190 and stayed for a few minutes, then quickly (1-2 minutes) rose to about 220. Felt the risers and intake manifold. They were warm, but I could hold my hands on them. Look again at the gauge...it jumps to 240. Head back to dock and kill it. Wife backs truck down. Start it back up and its sitting at 190. Beginning to think temp sender or gauge. Regardless, I don't want to risk a motor, so I dropped it off at Malibu dealer (closest Indmar service center) and told them to figure it out.

[deepcove]

txduckman

Are you by any chance running a closed cooling system?

[DOCDRS]

UPDATE!

Tried one more thermostat. Seem to have good impeller flow as no water spilled from fake-a-lake (all came out of exhaust). Even ran it briefly with intake house off of thermostat housing and seemed to have good pressure. Ran it on a fake-a-lake for about 25 minutes. Warmed to 185 and stayed rock solid. Problem fixed....so I thought.

Fast forward to saturday. Took it to the lake early in the morning hoping to beat all the traffic. Launched and idled out of the no wake area. Temp climbed to about 190 and stayed for a few minutes, then quickly (1-2 minutes) rose to about 220. Felt the risers and intake manifold. They were warm, but I could hold my hands on them. Look again at the gauge...it jumps to 240. Head back to dock and kill it. Wife backs truck down. Start it back up and its sitting at 190. Beginning to think temp sender or gauge. Regardless, I don't want to risk a motor, so I dropped it off at Malibu dealer (closest Indmar service center) and told them to figure it out.

your boat and motor would help. fake a lake will not give you real lake experience as you are pushing water thru the system....... in the lake it is all suck from the impeller......check all connections for tightness pre impeller.....and as papou mentioned make sure you have a rubber gasket in your strainer as this is another possible suction failure point as well as the strainer fittings.

[txduckman07]

02 Mobius LSV. 310 Indmar. I've suspected the strainer, but I haven't touched it since I bought the boat, and given this is a new problem, I'm not sure that could be it. Leaning toward temp sensor at this point given its erratic behavior. When the boat is warming up, it climbs slowly to 180. Then once it gets there, it might go quickly to 200+. Last saturday when I killed it, it was reading about 230. After sitting for only 1-2 minutes, it showed 180-190 upon restarting it.

[deepcove]

txduckman

Are you by any chance running a closed cooling system?

[txduckman07]

Negative. Raw water

[deepcove]

I had a similar problem to yourself. Temp would spike from 170 up over 200 and then back to 170 in about 30 seconds. I ripped my entire cooling system apart to check for debris ( I have a closed cooling system) only to find none, changed the thermostat, was looking into the temp sensor still with no sign of the cause. Turned out I had an air bubble in my closed cooling so I had to get the entire system burped and solved the problem. I guess this really does not help yourself but based on your symptoms it sounds like your raw water is getting though freely at times and some times not.

[newty]

Check for debris down stream of the impellar in the trans cooler? That would give you intermittent temp issues.