www.iFourWinns.com

1995 220 Horizon 5.8 EFI
Made a great run yesterday from Burlington, Iowa to Fort Madison, Iowa on the Mississippi. It is about 40miles round trip. My temperature gauge rairly got above 120. On the way back I ran it at about 4500rmps for about 10 minutes. The gauge made it up to 150 but as soon as I slowed down it cooled to under 120 again.

I am thinking the thermostat is stuck wide open. I'm taking the boat in this week to get winterized. Should I have the shop do it while they are in there or should I give it a try. This was my second trip out with the boat and the temp was acting the same when I took it out the first time.

I know my way around an outboard but I'm a little nervious about wrenching on this one.

Thanks, Shawn

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Shawn
Washington, Iowa
1995 Four Winns 220 Horizon

5.8 EFI 58FAPHUE

Could be the sender or gauge and not the thermostat. I would test those before throwing parts at the problem.

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Walter

2003 248 Vista - VP 5.0 GXi
2009 Toyota Tundra SR5 5.7L 4x4

I've seen the same thing on my last boat. It was just some "gunk" in the T-stat. You should be able to free it up just by running city water through it on the muffs for about 10-15 min before you winterize. It looks like the T-stat is responding, just being "sluggish". If that doesn't get it, have the T-stat checked out/replaced. Normal Op temp should be about 150, or 170. 120 suggests a failed (open) T-stat.

Also, get some pics of running on the river. Not too many of us on here!

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Walt B
"Debt-Charged"
Black '07 H210SS
6.2L Bravo One turning a 21P HIFive
Wakeboard Tower with Perfect Pass Stargazer version
Missouri River; Kansas City, Mo.

I've had this same problem, I run in salt water and the thermostats get sticky and do not close enough to let the engine run at normal temps unless it's running at cruising speeds. I wind up changing the 'stat probably once per season, even then it may not make it thru the season without it starting to stick. I am going to change mine before I winterize it because if I let it idle on the water hose to warm up it will not get warm enough even to change the oil (the oil will not pump out easily unless the engine has been run up to normal operating temp. So I'd have the shop change it just before they winterize it. If it's a 5.8 it's probably an OMC Cobra, the thermostats are held in with a rubber ring in the housing. You may have to clean off some corrosion to see it but with a small screwdriver you can pop out the ring and then put a new one it. I coat the threads of the bolts and the gasket with OMC gasket sealer (stays pliable) so they don't get corroded in place.

One way to tell if it's really the stat and not the gauge/sender, is to feel the hose from the thermo housing to the water pump on the front of the engine, if the thermo is in fact closing enough to warm up the engine, this hose should be warm to hot, and the thermo housing itself should feel warm to hot. If both are cool, and the gauge reads cool, I bet the stat is not closing. For just about all OMCs and Volvos that are raw water cooled 160 is normal operating temps.

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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

Exactly what he said... I also use a point-and-shoot IR gun. They are less than $40, and great for checking actual temps on cooling hoses, exhaust headers, and trailer wheel bearings.
http://www.harborfreight.com/cpi/ctaf/d ... mber=96451

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Walt B
"Debt-Charged"
Black '07 H210SS
6.2L Bravo One turning a 21P HIFive
Wakeboard Tower with Perfect Pass Stargazer version
Missouri River; Kansas City, Mo.

Just as a follow up, today I winterized my old 88 Cobra. I was getting the same sticky thermo scenario were it would take a long time to warm up, or not warm up at all at idle in the water, only when running on plane. I pulled it out on Wed and ran it on the water hose, after about 1/2 hr the temp was still at 100 (bottom of the gauge). Thermo housing and big hose cold when running. Today I changed the thermo bacause the engine was running too cold to warm up the oil to change it. Took about 20 min, mosty scraping the old gasket off. Popped in a ner thermo, coated the gasked and bolts in OMC gasket sealer, buttoned it up and ran it again. This time it warmed up to its normal 160 in about 15 min running on the hose, water is cold from the house supply and the air temp here was only about 45 degrees today. As long as the bolts are not corroded in, it is an easy job.

As an aside on winterizing, and the question of to use AF or not, I can say that the thermo housing I put in back in 2003 (used 4 full seasons in salt water) had no flaking rust, just some surface rust. And I used the -100 no tox to back fill the motor after draining each year. So to me this suggests that at least for raw water cooled motors in salt or brackish water it's worth it to use AF.

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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

+1. I've got one RayTek (now Fluke) in the tool bag at home and another in the truck. It's a great tool to have.

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Mike
2005 Four Winns 230/240
VP 5.7GXi/DP
1998 F-150 XLT
Boat Pic