Mercruiser 5.7 new manifold temp ?

[jamesbee19791]

Hi, I bought this boat about a month and a half ago. It's a 1996 Bayliner 2452, 5.7 Mercruiser with Alpha 1 gen II drive with a partial closed cooling system, manifolds are raw water cooled. This boat has seen mostly salt water use.

On the muffs it ran around 120 degrees before I bought it. Temp gauge is actually not accurate so I found. First trip out it stumbles an dies, seems to have overheated, let it cool down, it starts, I motor back to the dock and trailer it home.

Replace exhaust flappers and impeller, pull drive to check for flapper remnants in exhaust bellow. Fire it up on muffs, runs great. With an IR temp gun, starboard manifold is at 110 ish, thermostat housing about 145 to 150 then it drops. Seems good, shoot port manifold its at 215. I had the risers off when I changed the flappers, looked rusty and a water jacket was partially clogged. New manifolds and risers. starboard manifold is at 110 ish and port started climbing, I shut it down at 175. I pulled the drains on both and the port side had more water than the starboard side come out. Was thinking a clogged heat exchanger, but with the manifold draining water, am I over thinking this? I read a bit and understand they wont be the same temp, garden hose might not have enough pressure . Any thoughts? Thanks in advance

 

[alldodge]

Howdy

A garden hose will not supply enough water to keep both manifolds with equal amount of water. I think your good but should check your readings in the water.

 

[Blueghost924]

I pulled my intake manifold off my 1986 5.7L 260 and the water passage above the #8 cylinder is almost clogged. Well, actually both sides looked bad. Don't know if this would be a cause for your issue but it is food for though if you don't find anything conclusive.

 

[Bt Doctur]

there are no manifold water passages for #7 or #8 cylinder area

 

[jamesbee19791]

AllDodge had it spot on. Put it in the water, ran it to temp at the dock with rpm at 1100 or so. Once thermostat housing was at 150 the manifolds and elbows were both around 90. Ran it for 30 minutes at 3100 rpm down the river and took temps again, both manifolds and elbows around 105 or so. Thanks for the good advice!