overheating 6hp merc

[medicJD100]

I have a 65 merc 6hp.I just replaced the impellor in the pump. Still overheating.See nothing that resembles a thermo and have looked for obstruction. Motor sat foe 4 or 5 years, any ideas please? Thankyou

 

[Franki]

Re: overheating 6hp merc

are you sure its overheating? <br /><br />can you touch the head for 5 seconds?<br /><br />what I did with my 6HP (Chrysler but the theory is the same.), was took the leg off, and attaced the hose to the actual brass pipe running into the powerhead.. from the water pump.<br /><br />then I turned on the tap, started the motor and it blew out a sh!t load of mud from the outlet and the exhaust relief holes..<br /><br />Thats how I ran it to tune it too since it got better cooling then it did on the muffs.<br /><br />from that point on, it never got hot again, even under extreme loads, (like pushing a 17 foot halfcabin against wind and tide for 3 hours without a push prop.)<br /><br /><br />rgds<br /><br />Frank

 

[Chinewalker]

Re: overheating 6hp merc

Hi Medic,<br /> I think Frank is on the right track - trouble shoot it by checking to make sure that the water passages are clear and free of debris. This includes the intake water tube from the cavitation plate pickup. At the very least hook some comrpessed air up to the lower unit-to-powerhead tube and make sure you have a through circuit. <br /> When you removed the old impeller, were all of the blades accounted for? I've had old impellers disintegrate and pieces get forced up into the powerhead where they snag and block the flow. Also, make sure that the impeller key is in place and grabs the impeller. I've had Merc driveshafts get rusted a bit - enough that the key sits too far from the impeller to engage it.<br /> Finally, make sure the water tube is securely and squarely seated in the top of the impeller housing.<br />- Scott

 

[skier]

Re: overheating 6hp merc

These guys are definatly on the right track, although I never would have thought of running the engine without the lower unit and a hose attached to the pipe. I have done it without running the motor though and believe me, the city water pressure is a whole lot more than the impeller can ever do. (Hint don't use full city pressure) It's a bad thing. I blew the water pressure guage and hose right out of the fitting, but I got the blockage out