Merc 120 Hp (3849449) overheating

[Leedanger]

I have a merc 120 hp model 3849449 that seems to have a cooling issue. The temp climbs to 180 degrees very quickly, i would guess that it would keep climbing but I haven't wanted to over heat the engine. I figure it's either the impeller, but this test was done on the muffs so my thoughts were that issue would be overridden or the thermostat.

I am unfamiliar with this exhaust manifold and inlet hose. On my 140 the inlet house connects directly to the therm housing in the front of the motor. On this one the inlet hose connects in the back of the manifold where there is also a second hose that just goes in a loop or so it appears. Maybe I have it incorrectly installed?

 

[Bondo]

Re: Merc 120 Hp (3849449) overheating

On this one the inlet hose connects in the back of the manifold where there is also a second hose that just goes in a loop or so it appears.

Ayuh,.... Got a picture,..??

 

[Leedanger]

Re: Merc 120 Hp (3849449) overheating

I'll go take one right now

 

[Leedanger]

Re: Merc 120 Hp (3849449) overheating

View attachment 100538View attachment 100537

Sorry these are below par pictures as well as sideways. Hopefully ou can see that hose that loops in the back, it loops from the top of the exhaust manifold riser to underneath the riser and just above the water inlet hose. I'll try to get a better picture if these still don't make sense. You can't see the inlet hose from the transom plate in either picture, it's short because it connects in the back and it's also hard to see being that it is under that other hose.

 

[tejastoolman]

Re: Merc 120 Hp (3849449) overheating

you can quick check the thermostat in a pan of boiling water on your stove using a thermometer for cooking, and the t-stat will open... but if you never changed the impeller that's always the best bet and they are easy to replace with simple tools and a good video or two on www.youtube.com that's where I learn to do mine years ago and it's saved me a lotta wasted hard earned beer money

funny thing to see 7 people in line at the boat shop buying $250.00 mercury starters & impellers this morning... gremlins are hitting hard this holiday it seems like