Logo
FULL SITE MENU

Mercruiser 350 1 side running hot

T

thekude

New member
Mercruiser 350 one side runs m

Mercruiser 350 one side runs much hotter than the other Temp gauge does not show over heating. Replaced the manifolds and elbows already. It did not fix it. Checked the separator and thermostat not blocked. Ran the motor with the returns off from the separator and the cool side water flow ran strong but the hot side had half the water pressure. I do not think it’s the water pump or impeller since there is only one of each and has great pressure on one side. Any idea? Help!!!
 
"Alpha or Bravo OD?

" R

"Alpha or Bravo OD?

" Ran the motor with the returns off from the separator and the cool side water flow ran strong but the hot side had half the water pressure."

Are you saying you disconnected the hoses from the T'stat hsg. assy.? It is normal for one side of the exhaust to run warmer than the other. Can you lay your hand upon the hot side and not have to pull away due to the heat? Which side is hot?

Is the sleeve, item #6, in the correct position as shown in the diagram?
http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=81659698&ivar=images/COMM ON/14012.png&inbr=2697&bnbr=110&bdesc=Standard+Cooling+System"
 
Its a Bravo 1. The starboard s

Its a Bravo 1. The starboard side has the heat issue. I ran it for for 10 seconds with the 2 smaller hoses of the separator. It is normal for 1 side to rub a little hotter than the other but its really hot. I can keep my hand on the outside of the exhaust on the port side no problem but the starboard side you can not. I will check #6 tomorrow and let you know. I appreciate your time in helping me with this.
 
I took the separator apart. Ev

I took the separator apart. Everything was clean. Is it possible for 1 side of the impeller to be damaged and not for enough water to the starboard side? The port side water flow was strong. The only reason I can see why 1 side is hotter is because lack of water flow. But what is slowing down the flow?
 
John:

"Ran the motor wi

John:

"Ran the motor with the returns off from the separator and the cool side water flow ran strong but the hot side had half the water pressure. I do not think it’s the water pump or impeller since there is only one of each and has great pressure on one side."

Only things left are the impeller is weak or bad exhaust casting. I would replace the impeller 1st. It's strong enough to push enough water to cool the engine but can't push enough water to the hot side. You may be able to move the elbow to the other side to see if it changes.
 
Hi Guy:

I sent the boat to

Hi Guy:

I sent the boat to the repair shop since the impeller is beyond me to replace. If I did the impeller it would have ended up at the shop anyway. The shop replaced the impeller (little dinged up and seaweed stuck to it) and traced all of the water flow lines to make sure there was nothing stuck or blocking the water flow and the problem still exists. The shop called Mercruiser and they down played the GLM aftermarket exhaust I just put on and blamed that saying the ports may of been mis manufactured. I do not believe that is the problem since it existed with the Mercruiser exhaust. Water pump was checked and is fine. Shop tried a new thermostat and separator and it still did it. Any other idea's? Thanks again John
 
"Hi Guy,

Thanks again for a

"Hi Guy,

Thanks again for all of your help. The shop ended up replacing the impeller and the water pump. The problem was corrected after these 2 items were changed. The impeller had slight damage on 1 side along with a piece of seaweed wrapped around it. Wish I checked this first before putting on new exhaust. Regards, John"
 
"Well, at least you know it wo

"Well, at least you know it works and you won't need new exhaust for a long time. Did you keep the old exhaust? Have them cleaned at a radiator shop and paint them w/engine spray enamel. Spray the inside w/engine fogging oil and put them on the shelf. Coat the block mating surface w/some grease so they don't rust."
 
Back
Top