stumped on overheating

[LIstriper2600]

omc 5.7 GLI overheats at idle and under load. changed water pump on engine (was shot) checked circulating pump (ok) changed therostat.replaced risers (cloged) no steam from engine. engine protection kicks in when it gets hot and only runs ok at 1500rpm. could it be that the manifold is cloged?.... thanks Ed

 

[a.d.mobile]

Re: stumped on overheating

Look at the back of motor locate pwr steering cooler remove hose stick finger inside and check for weeds you may have to follow the lines from the pump to find it. sound's like restricted flow.

 

[LIstriper2600]

Re: stumped on overheating

I checked it but I will look at it closer<br />thanks

 

[LIstriper2600]

Re: stumped on overheating

I need some more Ideas please

 

[a.d.mobile]

Re: stumped on overheating

Look at collers good dont be fooled by the easy things. next place a pice of clear plastic hose from sea pump to t-stat housing check for air bubbles caused by a air leak in the intake system <br />some bubbles will be present as rpm go up it should be a solid mass of water flow. No clear hose remove supply to t-stat housing start engine in lake hold hose straight up the water should come up about 2 inches at idle like a garden hose.

 

[Boatist]

Re: stumped on overheating

If the risers were plugged very likely manifolds are also. I would think you would have seen that as they plug right at the exit going into riser. First is it a Cobra or a Series 800 and what is the year??? I would start by pulling the hose off that comes from outdrive and connects near the thermostat. Run it over the side or in a big bucket. Start engine should have a good flow of water there if not Recheck the water pump installation. If have good flow from outdrive next pull at least one hose going to exhaust manifold. Should have same flow there as input but can be hot water when thermostat open. With that hose off if manifold is plugged the engine should cool down but the manifold will of course get hot. If have good flow and it still gets hot time to recheck the thermostat and circulating pump. Make sure thermostat is not up side dowm and it opens and that circulating pump belt is tight inpeller not rusted off. If that all good I would do a compression check to see if could be leaking exhaust gas into water jacket.<br /><br />To stay cool need cool water pumped in the circulating pump to circulate water the thermostat to open and water to flow out thru the exhaust manifold and the riser down and out the prop. Good luck and let us know what you find.

 

[Paul Haldeman]

Re: stumped on overheating

I had what I thought was a serious overheating problem following a lower unit rebuild on my 1993 OMC Cobra, mounted on a Seaswril open bow. It ran fine under a load but burned up under 1500 RPM. After replacing the impeller, impeller housing, then circulating unit, thermostat, then, manifolds it still did the same thing. My mechanic took the boat out on the water himself and realized I was telling him the truth. He pulled off the new impeller and put in another new one and everything was perfect after that!!! I spent $2,000 to go back to the orgional repair. Fooled by a faulty impeller. Well the other repairs were on a boat that had 9 years of salt water so not all is wasted. My advice on your over heating - go check the impeller on your outdrive again. It's cheap, fast and sounds exactly like my symptoms.

 

[vinney]

Re: stumped on overheating

IF YOU HAVE SMOKED THE WATER PUMP THE BELT DRIVEN PUMP. IF ITS DISCOLORED FROM HEAT YOU MAY HAVE TO REPLACE THE PUMP ASY. THERE ARE SEALS IN THE PUMP YOU CAN REPLACE THEY ARE HARD TO FIND A PART NUMBER BECAUSE THE NEW PARTS BOOK DONT SHOW THE SEAL. IF YOU GO BACK ABOUT FIVE YEARS IT BREAKS DOWN THE PUMP. IF THE SEAL IS LEAKING IT WILL GIVE AN OVER HEAT AT LOW SPEED.THE BEST WAY TO CHECK A HEAT PROBLEM IS A HEAT GUN. VINNEY

 

[Walt T]

Re: stumped on overheating

If the impeller was in pieces, you must get all the pieces out of the engine or it will continue to overheat. It is considered a must to replace manifolds along with risers, assuming the manifolds are the same age as the risers. I suggest you find a different mechanic.