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1988 Johnson 6hp overheating/not pumping water

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whaler_warner

Contributing Member
Hi Guys,

Friend of mine is a marine engineer and was given this old motor to tinker with as apparently it used to overheat and the owner was just going to throw it in the trash, I now have it as my friend doesn't have the time or space and its been sat there for 3 years now!

Ive rebuild the carb, soaked the bores with oil for a few days, new plugs and she fired up first pull!! :)

However its not pumping any water being run in the tank and surprise surprise gets hot quickly. My friend said he looked at it briefly but as its so long ago he cannot remember what he tried but thinks he replaced the impeller and thermostat.

Ive removed the t/stat cover and theres no stat at all started it up and nothing coming out of the housing, ive run the hose into the housing and comes out the pee hole fine (so not blocked) but cannot see any water coming out the lower unit.

Job this weekend is to obviously remove the LU and check the impeller but anything else these engines are prone for blocking ie in the powerblock?
 
I have the same motor and know from experience, assuming its not the impellar then it's likely the ever notorious grommet at the top of the water pickup tube under the block which requires the removal of the whole power head. Its not a hard job but I was most worried about bolts snapping off.
 
Hint......when lower unit is off, blow some low pressure air up the supply tube, or you can rig up some water to check it from your garden hose or laundry sink. That way you can not only check for blockage, but a leak as well.
 
Thanks for the replies so far, ok so dropped the lower unit over the weekend and impeller is worn but complete and pumps.

I attached a hose to the bottom of the water pipe, turned on the hose and.... nothing. I tried to blow into the pipe and surprise surprise couldn't blow though so somewhere high up is blocked, weird as removing the telltale pipe I can blow down that and hear air hissing around the bottom of the powerhead. I am guessing its the grommet so guess theres no option but to remove the powerhead and investigate. I did remove 4 of the 6 powerhead bolts but two are stuck firm and I am convinced will snap off but have left soaking in penetrating fluid and will get some heat on it. Worst case even if two snap it looks like it wouldn't be too difficult to drill and tap ​
 
Okay, try this.....tap on top of the 2 remaining cap screws (bolts). Hit them straight in towards the powerhead....that's if you can get a decent swing at them. Then first try to tighten them. Sometimes this will break them loose a tiny bit. Now try to loosen them. Once you get it apart, fix your grommet, or whatever else is plugged, then be sure to replace those 2 bolts if you suspect that they were overstressed in the removal process. Clean all threads, inside and out, then install to proper torque using anti-seize compound. This is a beautiful little motor, they don't make them any more like these.
 
Yes, a few years ago I sold an older guy a 9.5 Johnson. I had just changed crank seal, water pump, and other tune up items. I warranty all my used motors for 1 full year. The guy called me and said that it was not pumping water. I drove 170 miles round trip.........only to find he didn't have enough water in his barrel. That makes ME a bigger fool than him. It's like.....DAH!
 
Just to (hopefully) conclude...

small impact driver made small work on the remaining two powerhead bolts, removed the powerhead and exhaust shroud to find the rubber grommet at the top of the water tube had folded over and blocking the waterpipe where it joins the block. New $3 grommet and a new gasket and it "should" be running fine.
 
whaler_warner said:
Just to (hopefully) conclude...

small impact driver made small work on the remaining two powerhead bolts, removed the powerhead and exhaust shroud to find the rubber grommet at the top of the water tube had folded over and blocking the waterpipe where it joins the block. New $3 grommet and a new gasket and it "should" be running fine.
Click to expand...

I got so fed up with that grommet that I modified mine. I used a couple of O rings and a couple of nylon spacers, which I made, instead .

You can check on that grommet's "health" though when you do a routine water pump impeller change. Push a stout wire up the water tube. If it keeps going 'til it hits something solid all is well . If you feel something squidgy at the top you know the grommet is beginning to close over it.
 
Sometimes we have to re-engineer this stuff, nobody's perfect. I have done the same thing with these, Vic. Also done improvements on the lower seals/o-rings of various models, even some Mercs.
 
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