How do I tell if the water pump impeller is working on my 9.8?

[oldrudedude]

I just purchased a 9.8 hp merc from a friend. He never had it running. He bought it last year from a neighbor. I put it into a bucket of water today and fired it up. It runs well but after running for a few minutes the powerhead and lower leg seemed to be getting quite hot. There does not appear to be a pee hole on this engine. How do I tell if the water pump is working? I have an old Evinrude and an old Johnson But this my first Mercury. It is still a bit of a mystery. Thanks in advance for the help.

 

[oldman570]

When running a motor in a bucket, make sure that the water level in the bucket is at least 5 to 6 inches above the cav. plate so the water pump will prime easy. Water should come out the holes in the rear midsection exhaust holes in a spray when the pump is working at startup. JMO
Oldman570

 

[racerone]

The tell tale often plugs up on these motors, but it will still cool properly.----Fact is that the impeller on these motors should be replaced every 2 years !!------There is also a plastic washer on the top of the water tube that often melts and blocks waterflow after a severe overheat.

 

[Texasmark]

Other thing is water temp. The water in the tub gets hot after running for awhile so keep a running hose in it. The hose also helps to replace the water you throw out when you put it in gear and goose it.

 

[oldrudedude]

Thanks for the relies. The problem is probably not enough water in the tub. Water was not more than 1" above the cavitation plate.

 

[racerone]

If pump was running dry it might be wise to inspect it now.

 

[Mi duckdown]

I would change the impellar, since you have no history on this motor. I'm sure it needs it

 

[oldrudedude]

I just put it into a larger bucket so that the water was certainly high enough to submerge the pump. Still no water spray from the exhaust bypass and engine powerhead is too hot to touch after couple minutes running. I will assume the impeller is toast. Where is T-stat on this motor. I should check it also. I need to find a service manual for this thing. Does anyone know where I could get one to download online?

 

[Guest]

what year is the 9.8? if you don't know please share serial #