www.iFourWinns.com

New question. I have two 305ci Mercs... one runs at 175 degrees and one runs at 100... any idea why one would be running cold? If I am not mistaken, 175 is where they should be with everything running normal. Both sound fine.

any ideas?

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Stacy & Isora in Annapolis, MD
2005 Vista 298

I too have the 305's on my 298 and they run at 175. Two things to check: 1) gauge, 2) thermostat. It is possible that you have a faulty gauge or an open thermostat.

I would tap it hard a few times with my finger to see if it is stuck in position. If nothing changes, you can open up the dash panel and swap the wires one for one from the know good gauge to see if there is a different reading. If not, proceed to replace the thermostat.

The gauges are made by Faria and they stand behind their product from what I have read on other boards.

Hope this helps!

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2002 Vista 298 VP 5.0Gxi

Good suggestion. I'll give it a try. have you changed a thermastat? is it the same as one in a car where you just remove the radiator hose from the block and pull it out?

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Stacy & Isora in Annapolis, MD
2005 Vista 298

No, I have not changed mine to date but it should be a do-it-yourself task.

The housing is similar in design to a car but with additional water connections. Cross reference your engine and model number to determine what the manufacturer recommends. The thermostat will likely be made out of brass. I would purchase from a marine dealer versus the automotive store. Marine thermostat normally have a stainless steel spring. You should also replace your thermostat gasket at the same time top avoid any leaks.

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2002 Vista 298 VP 5.0Gxi

I think you'll find it's your thermostat. It happens to me on one of my two (not necessarily the same) engines each season. When you remove it you might find a grain of sand, a flake of rust, or even some hard water deposits holding it open - it doesn't take much. I don't know how the Merc housings are machined but on the Volvo housings I have the thermostat is held in by an o-ring in the housing rather than sitting between the housing and intake like the automotive version. Either way, it's a diy job.

Joe

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USCG 50 Ton Master Inland/OUPV Endorsement+Towing

1998 278 Vista - Twin 4.3 GLs, Kohler 4KW Gen, AC/Heat.
1999 Yamaha Waverunner SUV
2003 Yamaha Waverunner SUV w/MR-1 HO conversion

Well, maybe it was just a piece of sand or something stuck in the thermostat... and it seems to have flushed on through... this weekend both were just fine sitting right on 175.

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Stacy & Isora in Annapolis, MD
2005 Vista 298

I was going to say, if you haven't had the boat out a lot this season, give it a few outings to see if it will correct itself. I too have one running around 100 and if it does not correct itself this weekend, then time to investigate.

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Current Boat: 2000 Four Winns 298 Vista
Previous Boat: 2000 Carver 406MY