low speed overheat

[markmarine]

I have a 40 hp Honda that overheats at slow speed, I have installed a complete water pump kit, (base, plate top and all gaskets). The water tube seals looks good, I taped off the upper pick up to make sure it wasnt drawing air somewhere. I have removed the thermostat to eliminate blockage. the alarm still goes off after running at slow speed, if I speed up it, the alamr stops and it pumps water.

 

[kandil]

Re: low speed overheat

Hello and welcome to iboats did you put back the thermostat? it is not a good idea to remove it. and is this happening in the water or on muffs?
(I taped off the upper pick up to make sure it wasn't drawing air somewhere)that does not sound right.
maybe you have some part of the old impeller left in the water passage I assume you changed that too?right? was it complete? sorry you got more questions than answer

 

[Mas]

Re: low speed overheat

Is the motor actually overheating? Can you leave your hand on the block near the spark plugs for a three count? Otherwise and as mentioned , you may have some debris in the cooling passages that limits cooling at low rpms.

MAS

 

[markmarine]

Re: low speed overheat

I took the thermostat out to see if it was restricting the water flow at low speed in any way. the alarm goes off on the muffs or in the lake. You can't hold your hand on the engine, it gets hot. I did install a new impeller in with the kit, I checked to make sure it still looks ok, I taped off the upper water pick to make sure it wasn't drawing exhaust in at idle, just trying to eliminate possible causes. There were no pieces missing when I changed the first impeller, I replaced it because of the overheat warning. There must be a blockage just enough to slow water flow at low speed, I was hoping someone had experienced the same problem with this model and found the causes.

 

[Mas]

Re: low speed overheat

Drop the LU and attach your garden hose to the copper pick up tube. You may need to jury rig an adapter. Turn the water on and see what flow you're getting. Run the motor and see if it get hot as before. Do not overheat it, however. This way you can determine where the problem is LU or motor.

MAS