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eyekode

98 monsoon thermostat question

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eyekode

Last weekend I took my sportster out and had a great weekend. But I noticed the temperature never made it over 145. I have not owned this boat long but I usually see 160-170.

I am wondering if the thermostat is stuck partially open?

Now to the question: if I remove the thermostat to check it what do I need on hand? Do I need a new gasket? Is there a difference between the automotive gasket and the marine?

If I can source it locally I will check it this weekend. I figure running at 145 for another couple hours shouldn't be damaging. This weekend is it is nice and warm and I don't want to give up time on the lake unless I must :).

Thanks !

Salem

Edited by eyekode

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zone 5

all you need is the gasket. I don't believe that Indmar uses any metal in theirs to ground like Mercruiser does. So any auto parts store will have one. If not you can get away with RTV silicon. The motor running at 145 is not going to hurt anything.

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Andrew63

The potential trap if it is sticking, is it could stick closed.

I picked up a 2011 RLXI with 250 hours & about a month back noticed stem from under the motor box cover.

Temp was up, but not to the point the alarm went off.

Split one of these hoses which rum from the thermostat housing to the exhaust manifolds, the one with the 90 deg bend.

Hose temp prior to the transmission cooler was cold and after quite warm t hot to touch.

Impeller replaced a few weeks prior. Checked the trans cooler for derbies from previous impellers, all clear.

Did not pick up a bag or anything, the boat ran fine back at a normal temp the rest of the day.

Picked up a replacement thermostat as I figured, if I was going to remove the thermostat housing to check, may as we'll replace it.

Before fitting the new thermostat, put the old & new one in a pot on the stove top to check thy both opened.

They did, but the old one opened more, which explained why the old one ran a bit cooler. The old one did not close which let me to believe it may be sticking.

Fitted the new one and temp has been more consistent 160 deg +/- 5 deg.

For the price of a thermostat, particularly if you don't know how old the existing one is, cheap insurance to change it once in there.

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eyekode

Thanks I think I will. We are unlikely to get any more 80 degree days anyway so my season is most likely done :(.

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malibuparadise

all you need is the gasket. I don't believe that Indmar uses any metal in theirs to ground like Mercruiser does. So any auto parts store will have one. If not you can get away with RTV silicon. The motor running at 145 is not going to hurt anything.

I made gaskets for my mercruiser thermostat housing (the style with plastic balls). See below link.

http://www.go2marine.com/product/77627F/thermostat-housing-mercruiser-87290a23.html

With no metal in the gasket is there a problem? Does the metal act to ground the housing temp sensors (alarm and gage)?

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zone 5

With no metal in the gasket is there a problem? Does the metal act to ground the housing temp sensors (alarm and gage)?

Thats what Mercruiser said, but I never had it on my Merc engines, and all the senders worked fine.

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