www.iFourWinns.com

replaced a new impeller on my 2008 H190 Mercruiser 4.3 Gl-J SX-A (first time its has been replaced). The first time it was on the lake sounded like no water was flowing through the system and sounded like it was running hard (this lasted only a few minutes and only this one time), then saw that the fresh water flush cap was off, after i screwed it back on, water started pumping through the engine and normal operating temp lasted all day, does this need to be an entirely closed system for the water to pump through?

Since then every first run of the day it overheats until running speeds where normal operating temps maintains the rest of the day (even after sitting after 2-4 hours). Does the impeller swell that much where the shaft wont turn when it sits for a few days? Does this sound like a water pump issue? All other fitting are tight and no water is in the bilge after all day.

So not sure why the engine overheats when we take it out every 3rd day on the first start, then at running speeds it cools and lasts all day at normal temps and engine sounds great. We run in very clean lake water. Any help would be appreciated

(First start of the day the engine warms up and starts to overheat, once the gauge starts to overheat i get the boat up to running speed almost 1/2 to 3/4 throttle and then cools down and for the rest of the day it runs an operates perfectly even after sitting for up to 3-4 hours before starting again).

I had a similar issue on a boat last year, ended up changing the water pump to a new one and problem gone. I inspected that pump as good as i could and saw no issues but something was wrong with it.

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Brian Borchik
The Winds of Cold Springs Harbor Marina
Baldwinsville, NY

that is was thinking but was unsure, im glad im not the only one out there with this problem, i will replace the water pump, how much did yours cost?

Any others have any thoughts on this topic?

Thanks Again

The cup the impeller sits in should be replaceable, no need to buy a whole new pump as long as the shaft doesn't leak. If that surface area isn't 100% smooth water could be going past the impeller blades causing your cooling issue.

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1981 Columbia 8.7
2015 Yamaha FZR - 87mph - sold
2006 Yamaha GP1300R - sold
2003 Chaparral 215 SSI - sold
2009 Stingray 195CS - sold
2000 Four Winns H180 - sold
1976 O'day Daysailer II - sold
Rick's Four Winns H180 Mods/Upgrade Thread

another friend stated the cause could be a fried t stat that failed in the closed position, then a burst of cold water resets it every time, mechanically this makes more sense, however if this does not fix the problem the water pump will be my next thing to check, thanks again for your help, i will re-post this topic once i figure the problem out to help others also