1988 v4 110 overheating

cookbayou

Seaman
Joined
Apr 20, 2009
Messages
50
I decided to change the thermostats about 2weeks ago. When I got to them they were stuck open and rusted pretty bad. So I finally got the new ones installed which was a real pain in the wazoo with the bubble exhaust in the way. I figured got the callon off might as well do the water deflectors in the block. That was simple compared to the tstats. Anyways got everything back together Friday night fired it up warmed up the motor on muffs and shut her down. Then Saturday afternoon retorqued the heads. Saturday evening I fired up the motor again on muffs and let it run. Then the overheat alarm sounded I shut it off and felt the heads were HOT. I was thinking there wasn't enough water flow so Sunday I took it to the landing and let it idle on the trailer every time the tale tell has been pissing hard. Overheat alarm again. Got home dropped the foot and impeller looks fine. Cracked open tstats housing to make sure tstats weren't backwards. Looked good from what I could see didn't want to remove yet as much of a pain as they were earlier. Ran compressed air threw the water jackets and no clogs. And removed heads to see diverters were in the same place. Basically I'm stumped she ran great before. Maybe I got bad stats both heads are running hot.
 

Bosunsmate

Admiral
Joined
Apr 7, 2012
Messages
6,135
Does that one have the little hole in the thermostat housing? I make that a bit wider as if it clogs up or shrinks from oxidation etc then the t stats take ages to open and hence the alarm goes off
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
My 79 85 hp has two small holes in the thermostat valve body. Each hole lets warm water bleed to the back of each stat, heating them up and causing them to open. If one of these holes is plugged up- it will cause that side of the block to overheat- even with a good impeller and new stat. Most folks don't inspect these holes prior to reassembly. My 96 has but one, larger hole on that valve body that serves the same purpose. It's hard to tell just when this change occurred, as the part number did not change from my 79 85 hp to my 1996 model, but there was a change in this hole arrangement at some point during this time span. My impression is that the older, dual hole, valve body tends to clog/plug up easier than the later version. I'd probably run the engine and check the cyl head temps with a laser temp gun. Would be nice to know just which head is overheating.
 

cookbayou

Seaman
Joined
Apr 20, 2009
Messages
50
Life got in the way of this motor. Anyway just got around to pulling the tstats. They tested good went ahead and bored the single bleed hole in tstat body and filed a notch in the bypass values and replaced water pump impeller and housing. Hopefully I can get the heads back on tomorrow and do a test run and update. Thanks for the replies
 
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