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View Full Version : changed thermostat, one riser hot, temp guage all over


jdeml
06-26-2011, 11:23 AM
Ok weekend filled with this issue that has me confused (as always). I have a 2004 xtar with mcx 350 just to clarify. I replaced the thermostat this week due to overheating issues last week. I started her up in the driveway using a hose and bucket method, pulls water just fine but tmp guage is all over the place. sometimes start and shows 160 and shutting down it stays there then on the next start it will peg out past 240. After a couple ign. on and off will move it slightly one way or the other. My boat is a tad off on the trailer, left side a inch or so higher and the exhaust riser on that side is noticably hotter then the other. water is coming out less also on that side. I have dug around in there and could not find any blockages. impeller looks fine. no blockages in oil cooler screen. what do yall think. should the risers be hot to the touch? On my other boat they are always warm but never HOT. Im thinking mayeb the sending unit or guage is faulty but how should I trouble shoot. I dont want to start throwing money at it without knowing and the 4th is right around the corner.

73blue
06-26-2011, 11:46 AM
What exactly were your overheating issues last week? Are you sure it was the thermostat then? You can test the thermostat by putting it in a pan of hot water to see if it opens (full disclosure, I installed my thermostat upside down once and it did some crazy things. Could this be it?) Other than that, disconnect all hoses and run water thru them to check for blockage. The only way I know to check the gauge accuracy is with a thermometer. Someone else may have another idea there. If its pulling water good, then your impeller should be ok, but you can pull the hose off above the pump and check the flow to be sure.

jdeml
06-26-2011, 11:51 AM
What exactly were your overheating issues last week? Are you sure it was the thermostat then? You can test the thermostat by putting it in a pan of hot water to see if it opens (full disclosure, I installed my thermostat upside down once and it did some crazy things. Could this be it?) Other than that, disconnect all hoses and run water thru them to check for blockage. The only way I know to check the gauge accuracy is with a thermometer. Someone else may have another idea there. If its pulling water good, then your impeller should be ok, but you can pull the hose off above the pump and check the flow to be sure.

I was overheating and just thought to check the tstat last wekk which I found to be all rusted and worn out. So I just figured that was my problem. It was acting like it was sticking. Running 130-140 then one day ran pegged. Now new tstat and wanted to make sure so I hooked her up to make sure no leaks. It is pulling water but guage is acting all over now. Just want to make sure I dont have some faulty numbers Im looking at. In refernece to the risers being hot, whats normal. should i get a temp gun and shoot em to see what they actually are?

73blue
06-26-2011, 12:09 PM
I would think the riser temp should be pretty close to the temp on the gauge. Not sure about that tho. It still sounds like your tstat may not be opening consistently (or is upside down). IIRC you can run it without the tstat. The engine should run a little cool but it might show if your gauge is ok.

jdeml
06-26-2011, 12:34 PM
I would think the riser temp should be pretty close to the temp on the gauge. Not sure about that tho. It still sounds like your tstat may not be opening consistently (or is upside down). IIRC you can run it without the tstat. The engine should run a little cool but it might show if your gauge is ok.


Im positive that the tstat is in correctly. just went out to the boat and turned ign on and presto guage is showing 160 after sitting all night. turned it off and back on and wham-o showing 240. hmmm.

73blue
06-26-2011, 12:56 PM
Yep, sounds like the gauge

jdeml
06-26-2011, 02:22 PM
any ideas on how to check to determine guage or sending unit. Also I think I found the sending unit but it has 2 wires coming off it, a black with white stripe and a yellow. sound right? all the stuff Ive read says one wire.

jdeml
06-26-2011, 08:22 PM
im going to lowes to get a ir temp gun. I plan on using it on the risers and manifold to make sure my guage is broke and not really reading super hot. anyone have an idea of what normal riser or manifold temps should be?