Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermostat

[yourflorida]

Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermostat

I have recently worked on the lower unit, replaced prop shaft, and now I am frustrated that the water pump will not produce "telltale" flow. Overall the motor is very clean, maybe 100 hours total, no sign of wear at the pump housing or plate. No liner installed from factory.

New Impeller, installed correctly. Water flows well at the thermostat, removed cover at thermostat and much flow. Tested thermostat even though that cannot cause the "telltale" to fail.

Opened the "exhaust box", I do not know the name but it is the spot where the telltale is mounted. Much exhaust and a little watter, not nearly what I expected and water never travels upward into the telltale chamber.

The shop manual I have lists a pair of O-rings, above and below the impeller. There were none and there is no part number for such in any parts list I have checked. (even looking at many years and different HP, no such part).

I have only barrel tested the unit, but I am confident the motor is deep enough.

• Why can I get water at the thermostat BUT none at the telltale? Pressure too low? (huge flow at this spot)
• Should I get a "waterpump liner", is this the issue?
• Are these mysterious O-rings really needed above and below the impeller? (the only place they are shown is during the reassembly instructions in the shop manual I have).

Thanks to any all help you can give, I am stumped.

Rob.

 

[TOHATSU GURU]

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

It sounds like the pee port itself is clogged up. While the engine is running, stick a small piece of wire up it. Also, no one replaces just the impeller. Always use the kit as an old liner or wear plate will cause the new impeller to fail at a much faster rate.

 

[yourflorida]

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

It sounds like the pee port itself is clogged up. While the engine is running, stick a small piece of wire up it. Also, no one replaces just the impeller. Always use the kit as an old liner or wear plate will cause the new impeller to fail at a much faster rate.

I am WAY beyond that, one of the first things I tried was the old "wire up the pee hole" trick.

Note that even with the "exhaust box" (still don't know what that is called where the pee port is mounted ) cover removed I have little or no water at that point.

Why would I have enough flow/pressure to have water squirt out of the thermostat cover when loosened BUT none at the telltale pee area?

What is the symptom of needing to install the "pump case liner"? There is little visible wear and the unit does not have the insert from the factory? I understand the theory behind the liner and plate, but if inspection shows that it looks fine what would the help? (I think I will replace anyway, as per your post)

Anyone know anything about why manual lists 2 O-rings above and below the impeller but NO PARTS LIST anywhere for such O-rings..... strange.

 

[Sea Rider]

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Submerge tail on a bucket with proper water amount, test water pump with a drill connected to driveshaft and see how much water is being pumped out grommet. If poor pumping will need to change complete WP. Usually there's no small o'rings at lower or upper impeller, strange there are not even listed in the spare parts manual. How old is that horse, is it new or used, have ever had a severe overheat issue ?

Don't know or work with 4 strokes engines, does it have a long peeing hose connected to lower powerhead small tube ? If so, disconnect hose and poke a wire through tube, you could have a internal clog there.

Happy Boating

 

[TOHATSU GURU]

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

What manual are you using?

 

[pvanv]

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

What manual are you using?

What Elvin implied. Plus:

The NSF18B2 definitely MUST have a cup in the pump. Without that, your side clearance is huge. It also definitely does not have any sort of o-rings.

1. Get a real Factory service manual, 003-21041-0, SERVICE MANUAL MFS9.9/15/18A&B, $40.00, from any Tohatsu/Nissan dealer (including several forum members -- even me). Scrap the aftermarket manual (or use it as tinder for the wood stove).

2. Install a real, complete, 362873221M, WATER PUMP REPAIR KIT 9.9/12/15/18-F15/18-F20, $50.68, from any Tohatsu/Nissan dealer (including several forum members -- even me). Never do just the impeller. The kit will last longer and pump better.

 

[yourflorida]

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

What Elvin implied. Plus:

The NSF18B2 definitely MUST have a cup in the pump. Without that, your side clearance is huge. It also definitely does not have any sort of o-rings.
Done that, still no luck. Removed uptube during test and it flows tons of water. Cracked open thermostat housing and water is also gushing. BUT, still nothing out of the telltale. (I have inspected the "telltale chamber" and there is no issue found).

1. Get a real Factory service manual, 003-21041-0, SERVICE MANUAL MFS9.9/15/18A&B, $40.00, from any Tohatsu/Nissan dealer (including several forum members -- even me). Scrap the aftermarket manual (or use it as tinder for the wood stove).

That is the EXACT manual I am using, the confusion on the "o rings" was caused by me looking in the wrong chapter....

2. Install a real, complete, 362873221M, WATER PUMP REPAIR KIT 9.9/12/15/18-F15/18-F20, $50.68, from any Tohatsu/Nissan dealer (including several forum members -- even me). Never do just the impeller. The kit will last longer and pump better.

New impeller, cup, key.... the motor was never overheated, low hours, the only reason I was inside to begin with is the stupid Piranha propeller destroyed the prop shaft and gears.... Never again! God I wish we used "shear pins" again...

My theory is that the "telltale chamber" fills up and is pressurized thus giving the telltale stream... this does not depend upon the thermostat since it is before all of that. It just seems that I have enough pressure to get water to the top of the motor and the thermostat BUT not enough to pressurize the "telltale chamber"....

Another detail I have noticed, water is flowing out near the foot through a hole on lower unit and around the seam, cannot say that I have seen that flow before all of this work.

Still need advise. Please.

 

[pvanv]

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

I can't imagine that a correct prop (of any brand) could be the cause of internal LU damage. Something is odd there. The modern props use a rubber hub instead of the shear pin technology... that allows you to "limp home" at reduced thrust in the event that the hub shears. If you installed a solid ss prop (without rubber hub), that removes the "safety valve" of the hub, which could cause damage if you hit something with the prop.

Yes, the pee tube is before the stat. It is an indicator only... it will indicate when the cooling system is pressurized. To verify 100% whether there is stoppage in the telltale nozzle, remove the nozzle. That will allow the tube to flow freely. Likewise, if you suspect a blockage at the nipple where the tube attaches to the motor, ream the nipple with a stiff wire to confirm that it's clear.

Yes, since the vast majority of cooling water exits with the exhaust, you will see water coming out of the LU drains (and the middle of the prop hub) when the cooling system is pumping. Still, you should have a good telltale stream. That said, if the pump is not properly seated to the water pipe (or the pipe is not properly seated to the block), the pump will fill the "leg" exhaust housing, and when that is full, the remaining water that doesn't flow out of the drains can flow into the block. In that case, you will have great flow from the pump, but very diminished water through the block.

 

[TOHATSU GURU]

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Is this engine new to you or have you had it for awhile and the prostate pee is a new issue for you?

 

[pvanv]

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Re: Nissan 18 4 stroke, water pumping issues, no "telltale" but yes water at thermost

Is the water pipe seated at both ends? If not, you are pumping into the exhaust housing, and not into the block. If that's the case, it would explain why you don't have much flow at the exhaust cover (where the pee tube attaches to the motor).

Likewise, if there is a blockage (such as a broken-off impeller vane) stuck in the water pipe, or lodged at the oil pan gasket or plate, that could reduce flow. BTW, in order to get water to the stat area, it must get past the telltale area.