www.iFourWinns.com

So...my port engine was only getting up to ~125 degrees when it normally runs at 160-170. Starboard is still normal, oil pressure normal on both engines. Thinking it was an open thermostat I replaced it. I've verified with an infrared thermometer that the temp gauge is accurate (8 degrees higher at all temps than the outside of the thermostat housing).
Now, I finally found a chance to take it out on the water, when running at cruising speed my port engine only got up to 140-150 degrees while the starboard runs at 170. After slowing down and coming back into the marina, the port engine moved up to 170 degrees, same as starboard.
Before any of this happened, both engines ran between 160-170 degrees at cruising speed.
What should I be thinking about this? I'd like to make sure there isn't some other issue I should be checking into.

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1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD

It could be a temp sender reading inaccurately, or even some corrosion on the connector for the sender or the gauge. These senders work on resistance and corrosion will throw them off. Usually my issues with 'stats have been sticking open due to rust or sand, when I replace them it goes right back to normal temp 165-170...

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I did check engine temp with an infrared thermometer on the thermostat housing. Looked like it was accurate. So I don't think that's it. Also when I idled the temp slowly rose to 165, not a jump like I'd expect with corrosion

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1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD

I had that same thing happen to me once this summer. Checked the Riser temp with IR gun and it was ok. I didn't worry too much about it. By the time I got back to the dock the gauge was reading ok. Most likely cause is the temperature sender.

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2001 328 Vista "Nauta Dream 2"
AB Inflatable 10AL "Little Dreamer"
2000 248 Vista
1997 225 Sundowner


Mike

Weather,

Did you find out what was causing your issue? I have the same with my 298 using 5.0GXi's. Thanks!

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2002 Vista 298 VP 5.0Gxi

Nope, left it for next year. I was boating all weekend and covered around 105km and the issue remained. At idle speed (in and out of harbour) both engines run at 165, at cruising speed, port goes down to 140 and stays there till I go back to idle speed.
I'm wondering if somehow I put the thermostat in wrong and water is getting past when it's closed, although I'm not sure how I would have put it in wrong.
I can't think of of what else would cause a cold engine.

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1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD