Overheating Mercruiser - Running cold one minute @ 75 degrees then running hot at 195 degrees Weird

[@MrKurtmack]

Thanks a lot for KZbin video on the overheating and the temperature gauge going up and down when you figured it out. It was the water pump mounted to the engine. I had the same similar problem and you saved me a lot of time I changed it and I’m back to normal.

[@robertwinterstein6690]

If this engine was in a road vehicle with a radiator, we would be doing a combustion gas test with a block tester with all of the gasses bubbles shown in the cooling system.

[@quadzillaandy]

No water check the seal on the water pump. That is were the air is coming from. Solid stream be hind the water pump air after.

[@AVERYhornyMrDinosaur]

in a manual for a GM 4 cylinder 3.0L mercruiser i read, it said that if your overheating above 3000rpm, to use clear hoses like this and if you get cavitation like this then it was a head gasket. my guess is either the engine's pump or a head gasket. we are having the same problem, but haven't checked our boat yet. i expect to see the same as this. i'm sure you fixed it by now, what was it? quoted from the book: "A blown head gasket(s) normally cannot be detected by a compression check. Normally the engine will run at normal temperature at low rpm, but will overheat at speeds above 3000 rpm. Engines that are seawater cooled: Using a clear plastic hose, look for air bubbles between seawater pump and engine. If there are no bubbles present, install clear plastic hose between thermostat housing and manifold(s). If air bubbles are present at a higher rpm, it is a good indication there is a blown head gasket." edit: in the video you said it wasn't running between the thermostat and the manifolds? so it must be the pump right?

[@joemitchell5565]

circulation pump/ water pump on front of engine OR the flapper split on the exhaust side

[@arthurgay5746]

Looks like a head gasket to me !

[@Comprezzed]

Free spinning circulation pump impeller. Just like my boat.

[@rockerneck]

Agreed. I’ve seen the impeller crack in half.

[@gotfish4190]

Comprezzed: what do you mean by that?

[@Comprezzed]

@@gotfish4190 kzbin.info5Zr5Y_Bde4U

[@NinjatoKid]

A little late but did you get what he meant by that?

[@Comprezzed]

kzbin.info5Zr5Y_Bde4U

[@captainchrisfishing]

your a professional marine service coming on youtube asking for help solving a problem ? just wow

[@7amood.alharthi]

I was running my alpha one 2nd gen mercruiser 4.3l in idle the temp reach 180F but with crouse or increse the rpm directly gone down and cool what is reason ???

[@brettowen4243]

Clogged heat exchanger ?

[@mikedodd9294]

Could be the 2nd water pump, the water circulation pump. Just replaced mine under $100 for a "marine" one. Recommend painting it before putting it back in as they rust pretty quick in salt water slip.

[@francisconunez8610]

You did it after replaced the outboard impeller? Or no?

[@HEATHAVIS87]

Head gasket

[@evanbushong4291]

What if there is some air? Having over heating issue

[@PRECISIONMARINELANIER]

I bet you money exhaust shutter valves have broken and wedge themselves in the y-pipe. Preventing exhaust flow and water flow creating an air pocket. Causing the egts to rise and thus making the boat run hot and cool depending on how those rubber flaps are allowing water to exit... And I bet you anything that ends up breaking your circulating pump impeller wheel... Sometimes these flaps will get dislodged.. and fix itself and you not see an issue again.. or they create enough back pressure to break the impeller wheel on the circulating pump..

[@PRECISIONMARINELANIER]

Bet you anything is the exhaust shutter vawser broke loose and wedge themselves down in the y-pipe

[@georgevoigt3883]

I was running my alpha one merccruiser after replacing impeller water pump thermostat it ran cool at idle and at low cruise speed through the bay however after putting it under a load it got hot then cooled when I dropped it back down any ideas

[@mikedodd9294]

what was it

[@iranick21]

Did you ever figure this out mines doing the same exact thing

[@mmonte60]

What was the diagnosis? Impeller? My alpha 1 is doing the same thing. Thanks!

[@mrpounds1980]

Mine is doing same thing anyone ever figure out out?

[@homeranievas5482]

Cylinder head gasket need to replace

[@nickb8618]

Circulation pump 100% on the front of the engine

[@keepitreal5148]

Water circulating pump is bad

[@johncasor9698]

@8:51 you say the year is january 20 two thousand , Haha... that is a long time ago... your problem is ??? over heating ??? or just a bad temp gauge ??? head gasket is on wrong blocking coolant flow ??? has anyone just installed head gaskets ??? .

[@mchaves7663]

Have you found the problem?

[@Sea2SeaAdventures]

Engine water pump. Not the sea water pump.

[@mchaves7663]

@@Sea2SeaAdventures did you replace the impeller in the water pump?

[@Sea2SeaAdventures]

@@mchaves7663 Not my boat. He stated it in one of his other videos. kzbin.info/www/bejne/p4W5iYRoa7umfac