Nissan 15 HP 4 Stroke water pump

[SprocketDog]

First of all, I just bought the boat

Jon 16ft with Nissan NSF15B motor (2002 15 HP)

I knew the original owner and fished with him several times. I doubt he used the boat more than 30 times since he bought it new in 2002.

I can't remember while with him just how much water came from the tell tale but now that I own it, I don't see any so I replace the water pump base plate, impeller, and cup but no improvements. I can lay the back of my hand near the TT and hot exhaust comes out with a slight bit of moisture.

I checked the thermostat on the stove and it opened according to manual specs
I removed the plate on the back to expose the passages for exhaust, tell tale hole and cleaned the pump output tube plus TT tube, blew thru the block passages to and from the thermostat housing and all are good and clear

It looks to me this model can't tell tale until the thermostat opens but brought to temperature it still don't

I again removed the lower unit and double checked the rotation of the impeller and it's right and while out, I coupled a drill to the shaft with a rubber hose and a small hose in the output and it squirted water a full stream even lifting the hose 5 ft above

The thermostat I'm sure is opening because I took the cover off while still hot and was open about 1/4" and it had to close some while I was doing it.

I read where it will telltale when first started (Cold or Hot) but I can't see how it can cold with the Thermostat blocking the water circuit

I ordered a new thermostat with the pump parts but they shorted my order and hopefully get it sometime later

I'm looking for some help here and the truth about will this pee cold and how much warm or what my problem is

I'm quite sure the engine never got hot anytime and runs like a purring kitten

Thanks
Sprocketdog

 

[pvanv]

Re: Nissan 15 HP 4 Stroke water pump

Yes, the telltale should flow under all conditions, hot, cold, etc. If you are getting exhaust from the tt port, the exhaust is backing up into the cooling system, which would be typical of a lack of water pressure from the pump.

If you are sure that you installed the correct impeller (did you get a complete kit, was it a tohatsu/nissan part?) and it pumps OK with a drill motor as you mentioned, you may have a problem with the water pipe. It's possible for the water pipe to not align with the pump as the LU is raised into position. You will want to check that alignment very carefully. If not aligned (slightly bent pipe), the pump will merely fill the exhaust housing, rather than pressurize the cooling system.

 

[SprocketDog]

Re: Nissan 15 HP 4 Stroke water pump

Thanks pvany for the come back

I have double tripple checked the output pipe and even totally removed it and flushed it out. I slipped the bare pump over it to check for fit and seal and it seemed OK.

Here is where I get snowed on this open thermostat question, with the LU off and a converted rubber hose fitted on the pump output tube, I can't blow thru it without removing the thermostat first ( maybe just a little leaks thru).
By following the passage where the tube enters the motor, traces me to the spring side of the TS and from the (exhaust box ??) on the back of the motor a passage close to the exhaust hole traces me back to the dead side of the TS. Those are all free from blockage. I removed the TS and ran it and still no TT. Is there somewhere in the motor block a passage that bypasses the TS or my question is how does it get to the discharge compartment (box on back where TT comes from) with the TS closed.

I have checked for blockage in the exhaust that might back pressure the water flow.

PS: Water Pump Repair Kit 362873220M from East Marine

Thanks for the help

 

[RadarRick]

Re: Nissan 15 HP 4 Stroke water pump

Just a thought - you might check the top of the water uptake tube. There's a rubber grommet/fitting there that has to be positioned correctly. If it's not, it can block/impair the water flow.

I don't know if one can see it from below. You may have to remove the power head to do this. Maybe you could force a piece of weed-eater line up the tube?

 

[SprocketDog]

Re: Nissan 15 HP 4 Stroke water pump

Thanks all for the help

I found the problem, I removed the main cover that houses the thermostat, anode telltale output and found what looked like pieces of dried moss.
It wasn't really all that much but sure caused the problem.
Cleaned it all out and away see went full stream at idle.

Why that would let me blow into it and not put water out I don't know and don't care now.

 

[RadarRick]

Re: Nissan 15 HP 4 Stroke water pump

Thanks for the report - happy boating!