Nissan 5 hp overheat

[Whatfiero1]

Ok smart people I've had a little 5hp nissan/ tahatsu that I changed impeller cleaned flushed cooling passages and test run in fresh water but when I put in salt water it stops pumping water and over heats. Tried changing impeller again to see if it's slipping on hub. But stops pumping water 10 min after I leave the dock every time. Any idea what it is do they have thermostats is the salt clogging it it will idle all day at dock used a whole tank of fuel one day and dock mates kept telling me I left motor running but soon as I left dock quit pumping and overheating

 

[Will Gilmore]

Have you tried running it in gear in a trash can (use saltwater). Does speed matter, low, cruising, high speed? Do RPMs make a difference when in neutral?

-Will (Dragonfly)

 

[Whatfiero1]

Tried running in bucket seems to loose prime and stop pumping past 1/4 throttle

 

[Brian D]

You have blockage. Probably a small piece broke off and is preventing the flow. All it takes is a tiny piece you have have missed. I think the saltwater is just a coincidence.

Find the pee hole and remove the tube. See if water is coming out. If not, follow the tube and remove it from the motor. See if water starts to flow. If not, and if you have one, remove the thermostat and place it in a pan of boiled water. You should see the spring activate telling you the thermostat is working correctly. Also try starting the engine with the thermostat cover off. You should see water flowing.

JMHO

 

[JimInPB]

Is it actually overheating? Or is the tell tail just not spitting out water? If the engine head gets up over 200F, then you have a genuine cooling problem. If the head temperature levels off well below that (like 150ish), then I'm going to suspect that you just have a little blockage in the tell tail. Check to see if the owners manual tells you what temperature the thermostat should open up at.

 

[RoyS]

Look under the impeller. I have a different motor (Yamaha) but yours may be similar. On mine there is a pin that goes through the drive shaft and rotates the impeller. That pin slides out and permits you to remove a stainless plate that sits under the impeller. There is a cavity under that plate. On mine that cavity gets filled with some kind of jelly like sludge from the salt water. Clean that out and you will be OK.

 

[AWalker]

My best guess is a faulty T Stat, not opening sufficiently for the load.