1975 johnson 9.9 hp water pumping problem

snuffy45 · May 12, 2011

I have a 1975 Johnson 9.9 hp. model# 10R75C. last year it ran fine & pumped good stream of water, this year on test run it only spit water, I could feel air pressure at hole when I stuck my finger over hole while running it, good air pressure coming out bit just a spit of water & it was hot. been reading other posts about water problems, does mine have a thermostat? figured they all might have but read somewhere that my yr doesn't. where is the thermostat? going to try the weedeater string through hole & air compressor to. any suggestions please??? thanks

raczekp1 · May 12, 2011

Re: 1975 johnson 9.9 hp water pumping problem

http://www.sschapterpsa.com/ramblings/Ramblings.html

AEROCOOK · May 12, 2011

Re: 1975 johnson 9.9 hp water pumping problem

When was the water pump impellor last replaced? If you dont know, you should start with that.

snuffy45 · May 13, 2011

Re: 1975 johnson 9.9 hp water pumping problem

don't know when the impeller was last changed, I got the motor last year & started using it right away. thia year is when I had the problem. I was figuring I needed to change impeller. do I remove 6 bolts & drop lower section just above prop? watched a few videos on u-tube about it. tried the weedeater line & air compressor yesterday. in the tank of water when I blow air in hole there is good flow to intake water holes, all kinds of bubbles. but it just spits water barely. gets very hot so I didn't run it long. thanks for any advise.

the machinist · May 13, 2011

Re: 1975 johnson 9.9 hp water pumping problem

Since your motor is a 75 you do not have a true telltale (pee hole) like the 9.9s 1977 & later. Unless someone has modified yours. Your motor will have a large "blubber hole" out the upper center of the exhaust housing. This will have a mixture of exhaust gasses & water after the thermostat gets warm enough to open. Before the thermostat opens, it may just have hot exhaust gasses.

If you are trying to weedeater or air pressure in the blubber hole, it won't do a thing to help.

snuffy45 · May 14, 2011

Re: 1975 johnson 9.9 hp water pumping problem

I tried the weedeater string & air pressure through the hole where the water comes out. last year as soon as I started it there was a steady stream of water from this hole, now it only spits water, but when i put finger over hole there is good pressure being blown through it just very little, ran it for less than 5 min. & where sparkplug is I couldn't lay my finger there for just a few seconds cause it was really hot. I've read on here it has a thermostat & that it doesn't. I don't know & don't have any idea where. I'm pretty mech, inclined but need some direction to go in with this, can't afford the $$$ at repair shop but can't afford to buy another motor either. any help I thank you all for.

bktheking · May 14, 2011

Re: 1975 johnson 9.9 hp water pumping problem

Oh it has a stat, the stat could be bad or you have a blockage, common issue is the upper grommet tube under the powerhead. Pull the rear stat cover and inspect.

snuffy45 · May 14, 2011

Re: 1975 johnson 9.9 hp water pumping problem

where will I find the rear stat cover? when it is removed will I be able to see the grommet tube also. just don't know anything about a stat on boat motor. thank you

AlTn · May 14, 2011

Re: 1975 johnson 9.9 hp water pumping problem

go to marineengine.com for parts diagrams for your motor...use the link provided by raczekp1 ....the series was written by. LeeRoy Wisner" The Machinist" who has also posted to your question...a lot of knowledge and experience for free

Solittle · May 14, 2011

Re: 1975 johnson 9.9 hp water pumping problem

Get the OMC shop manual. It explains everything you need to know, has pictures & diagrams. You need to replace the water pump. They are relatively easy motors to work on. I have one.

bktheking · May 15, 2011

Re: 1975 johnson 9.9 hp water pumping problem

Read sschapterpsa.com, leeroy's rambling, you'll see the answer to your questions. Powerhead has to come off for the grommet.

OptsyEagle · May 16, 2011

Re: 1975 johnson 9.9 hp water pumping problem

OK. You have a T-stat and it is at the very back of the powerhead behind the plate that is behind your spark plugs. It is held on with about 7 bolts. There is a gasket there so try not to damage it when removing this cover or get a new one.

When you start your motor, water does not immediately spray out that exhaust hole. It takes about 15 seconds, until the T-stat opens before you should get a good spray. You also need to ensure the lower end of the motor is drop deep enough into the water because your water pump is not self-priming. It needs to go in at least 3 inches above where the lower unit meets the mid section.

1975 johnson 9.9 hp water pumping problem

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