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mariner 1990 9.9 hp won't pump water

sandblaster28

New member
I have a 90' mariner 9.9. Every once and a while it will pump a very small amount of water.I changed the pump and i'm getting water to the pump. the water pickup tube goes into a rubber tube or seal in a hole in the pump housing that seal is not completely tight and has a little slack. would this cause is from pumping water. I started the motor and stuck a hose to the water pickup tube and no water got to the head. Thermostat?:rolleyes: Or blocked where it goes to the head. I have a clymer but tells nothing about where water is routed to. any help would be greatly appreciated. Thanks for your time.
 
Re: mariner 9.9 won't pump water

Probably blockage. I am not sure if that small amotor had a thermostat or not. G. Lamb will know if he looks at this thread.
 
Re: mariner 9.9 won't pump water

If it's a Merc/Mariner then it DID NOT have a thermostat when it came from the factory although it could be installed as an "option".

I don't know if the Yami/Mariners shipped with a thermostat or not.

The water system is pretty simple on either version of the 9.9.

The water pick-up feeds the water pump which forces water up the water tube to the base of the powerhead (at the carb end of the powerhead).

The water is directed back through a couple of channels in the base of the powerhead then up into the water jackets which surround the cylinders (Merc/Mariners) or through the channels in the head (Yami models) - because of this, one possible cause of "loss of cooling water", assuming the pump and tube is ok, is a toasted powerhead base gasket (simply check the lower cowl for water).

Some is forced out the tell-tale (to let you know it's circulating) the rest goes right out the exhaust.

Even if the motor is cold and the thermostat is closed you will still get water from the tell-tale - the thermostat regulates the cooling of the cylinders but is not like a dam that completely stops the water flow, there is a bypass channel in the powerhead which directs some water down the exhaust (to cool the exhaust and act as a muffler) which will also provide the flow to the tell-tale which is fed from the base of the powerhead.

So each time you start the motor you should get water from the tell-tale within a couple of seconds (the time it takes the water to get up to the powerhead from the water pump).

You say you changed the waterpump - did you put in a kit or just do the impeller?

Common problems include the cover gasket, the cover seal (rubber insert in the cover of Merc models - sounds like what you noted to be "slack"), the guide tube or the seal at the top of the water tube where it mates to the powerhead.

On pre-95 model's the water tube is flared at the top and held in place (at the powerhead end) by a plastic flange (which includes a gasket, rubber seal and a spacer) that is held in place by two screws (in to the powerhead).

The only component of the whole water tube assembly still available is the seal itself. So if the connection to base of the powerhead is the problem and it's not the seal (or if you have a hole in the water tube itself) then you have to go through a major pain of switching out the exhaust plate and tube and switch to the new style water tube (which still connects the same in the lower unit end) but requires the water tube guide hole in the exhaust housing to be drilled out to accomodate the new tube - about 100 bucks worth of parts and a good bit of labour - so you always hope the water tube/assembly is not the issue.

If the motor has been run in Salt, dirty or gritty water or in lakes with dissloved natural minerals (and then not flushed with fresh "hose" water after every outing) you can get a build-up in the water channels at the base of the powerhead.

Salt and minerals can be dissolved by using straight white vinegar - normally, I pull the thermostat cover, turn the motor so the water channels can't drain and then fill the head up with vinegar (works good up to about 25 horses then they are just too heavy to work with) :) - I leave the vinegar in overnight (at least) and it dissolves all the cooties without hurting the metal or any gaskets/rubber components.

You can use CLR or any number of "marine" products, but vinegar costs less than a buck a gallon at the grocery store and works every bit as well.

Your best bet is to pull the lower unit and jury rig your hose right up to the water tube. You should get good water flow coming right back down the exhaust housing (leg) "without the motor running". If not you have a blockage. If it's flowing well, then you either have a plugged up tell-tale or a problem with the waterpump (most likely the seals)......
 
Re: mariner 9.9 won't pump water

Early ones did not have stats. I do not remember when that started. If it does, then there will be two bolts that come out of the small cover that the pissser hose runs into. If the fitting is threaded right into the water cover than no. Very little water will come out of there until the stat opens in about 5 minutes.
 
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Re: mariner 9.9 won't pump water

Take a needle or a wire close hanger and jam into the pisser tube hole to unclog if you have water going everywhere else. Sometimes sand gets clogged in there and hardens. I have to do it every other year on my 150 and it has two thermostats.
 
Re: mariner 9.9 won't pump water

MSather: run your motor on the hose to flush it out and and you shouldn't have that problem any more. I am not being a smart ass, just want to let you know that if sand is there, then it is sticking other places where it shouldn't be.
 
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