800 OMC overheating

[THE BEEF]

I was at the lake today and I still have a overheating problem. 800 stringer 305 engine.<br />This is what I have done. Replaced sea water pump and housing, New thermostat 160 degree. At home with muffs on runs at 160. At the lake when you kick up the throttle temp starts to climb<br />then somtimes it drops right back down. this is what I checked. Pulled water hose that supplied sea water got flow. Pulled thermostat housing and took fan belt off no bubbles in manifold. Opened drain cocks have water flow in each side.put it back together with out therm.and ran it temp was about 120 as the throttle increased the temp went up to 180+ pulled back and temp went down.I pulled the pump on the engine and found it was replaced with an auto pump.I pulled the back cover off but I can't tell if the impeller is worn outThis problem started all at once. Anyone have an idea <br />thanks<br />Beef

 

[xltier]

Re: 800 OMC overheating

when mine did that it ended up being that the manifolds were partially plugged up.they always run cool on the muffs cause you have pressure feeding the pump.i found it with a non-contac temprature gun tool.hth

 

[THE BEEF]

Re: 800 OMC overheating

which manifolds?

 

[Boatist]

Re: 800 OMC overheating

If it is a saltwater boat I agree likely the manifold plugged.<br /><br />Both exhaust manifolds. Feel the manifold if it is hot Likely bad. If One is hotter than the other then pull that side off and check it first. Usually plug up where the mainifolds attach to the risers. If it is plugged up you can clean it out and will probably run cool again but before long the Manifold will rust thru and water will get to the vlaves and into the cylinders and you will be replaceing more than the manifolds.

 

[THE BEEF]

Re: 800 OMC overheating

Thanks.<br />The boat is fresh water Lake Erie.I pulled the risers off last fall to change valve cover gaskets and I checked the ports thay were clean.<br />I got the boat stuck a couple of times in the channel it's shallow. Could I have a plug port going up to the intermedit housing? When I pulled the hose off the them housing from the lower pump it had water flow but it didn't shoot out at idle. Im wondering if Im lacking pressure and volume?<br />Beef