Mercuiser 888 Running Cold

[ctanke]

Hey guys
I have a Mercruiser 888 that I can't get over 115 degrees even after running at WOT. New problem this year. Changed thermostat thinking the old one may have been stuck open - was no help. New gauge and sending unit, gauge reads about 115 ( I guess) but I put an infrared gun on the thermo housing, elbows, logs, and am also ready 115 degrees or thereabouts. Last year she'd warm up to 140 degrees after 10 minutes or So of idling. Where do I go from here?
Thanks in advance, Chris

 

[biggjimm]

I have a 77 complete 888 sitting on a pallet in my shop & the cooling system is just like my 79 260 mercruiser. It has what I think they call a warm manifold system. Cooling water from the engine goes thru the exhaust manifold & then after coming back to the T-stat housing it's sent to the risers & out with the exhaust. There is a block-off or restrictor plate between the manifolds & risers.
When I first got my 260, someone had the hoses on wrong & it ran cold.
If you've had the hoses off recently you might check the diagram in the manual & make sure they're on correct.

Only other thing I can think of is the T-stat but you checked that off the list already.

Some of the super smart folk will be on here later on & will have some more input.

Jim

 

[alldodge]

Is your hose routing like what is pictured below?

 

[biggjimm]

That diagram is how my 888 & 260 both are set up & when the hoses were on wrong it was all messed up. If I remember correctly mine were switched from side to side & the water was not circulating thru the manifolds. I think that's what it was.

After finding the diagram & putting them back like they were meant to be it's been fine ever since. I can even get it to temp & have the t-stat open on the muffs now. That's something my 140 won't do unless you regulate the water supply to a point where it's scary low.
Good luck.
Jim.

 

[ctanke]

That's it!
The two portside hoses on the top of the thermo housing were switched up.
Thanks much,
CT