More Johnson Problems

[duckhunter55]

This is probably about the 6th problem i have had with this motor. After changing the lower unit with a completley different lower unit, I cant get the motor to pump water. As i have been told, i 1st, took lower unit apart, replaced impeller put back together. nothing. 2nd bought new t stat, still nothing. 3rd checked all lower unit passages and the rubber grommet on top of pump housing. still no water. 4th used an air compressor to blow up copper pipe and then down t stat. When i blow into the tstat i can only feel air coming from pee hole line. When i blow through pee hole i feel it out of tstat. But i cant feel any air from anywhere when i blow through the 2 exhaust holes on rear of leg. When i blow up copper pipe i can feel it at t stat and vice versa. And lastly if i pour water down tstat it only comes out of the little tiny, i guess, lower unit drain off holes. Run motor at river and in bucket but still cannot get any water out of pee hole or exhaust holes. Also the drive shaft has the little key for impeller. And lastly i was told about a rubber grommet where the top of copper pipe goes which can sometimes swell and resrict water flow? Sorry for long post

 

[angus63]

Re: More Johnson Problems

model and year?
Did you replace the pump housing?

 

[jbjennings]

Re: More Johnson Problems

This may sound a little crazy, but here goes:
I had a merc 9.8 that was driving me nuts pumping water but not enough to suit me....I then tried this---take your lower unit off and slip a piece of fuel line over the end of the copper pipe that goes up the exhaust leg. Rig your water hose to the fuel line with some kind of fitting or duct tape or anything that you can devise that will put water into your powerhead under a little pressure when you turn the water on. Then crank your motor. If it's working fine, you know it's your pump, if nothing, then you have an obstruction in your water jackets or elsewhere.
Hope this was helpful,
JBJ

 

[bgbass.1]

Re: More Johnson Problems

Have you taken the pipe out of the water pump housing and ran water up that pipe? And if so how far did it go? what motor do you have?

 

[duckhunter55]

Re: More Johnson Problems

Sorry about that, I have a 1978 25hp Johnson manual start

 

[wbeaton]

Re: More Johnson Problems

Take off the lower unit and submerge it in a bucket of water. Attach a drill to the driveshaft and see if it pumps water. Could be a worn pump housing or restriction before the pump. Check to make sure the water passages and screen before the pump are clear too. No one ever does that.

 

[samo_ott]

Re: More Johnson Problems

When I put my 18hp LU in a bucket and spun it with my 330 rpm 1/2" drill the water shot up about 7-8" out of the pipe... just as an fyi.

 

[marinebarry]

Re: More Johnson Problems

Hi I just found this site.i am in need of a part in my hydro electric shifter any advice on where to look or how to adapt another electrical by pass

 

[HighTrim]

Re: More Johnson Problems

Marinebarry, you need to start a new thread of you own, stating your motor, model number, problem, etc... Jumping in on anothers thread confuses ppl.

 

[samo_ott]

Re: More Johnson Problems

I'm already confused!

 

[hammerhandle]

Re: More Johnson Problems

I would try removing the lower unit and try testing as described above, was the rubber vanes on the impeller going in the correct direction???

 

[duckhunter55]

Re: More Johnson Problems

Alright removed lower unit and stuck it in a bucket. Turned with a drill and no water shot out. Took pump housing off and checked impeller. Its in almost perfect condition. I cant figure out whats wrong. Screen is clear, holes are clear. Blew air threw them. Can the housing somehow cause this? Also the metal plate is in correctly. impeller is spinning inside housing. laslty when you stick lower unit in bucket do you fill up until it reaches the screen and 3 holes or do you go higher? This is driving me crazy!

 

[jbjennings]

Re: More Johnson Problems

You have to have the water level to the top of the water pump housing at least. I've even noticed sometimes when running in a barrel that the water level needs to be almost to the exhaust hole to make enough hydrostatic pressure to push water in to the impeller housing so it will pump right. But yes, you need to submerge the lower unit at least until water is above the impeller housing, preferably a little more. Are you sure the impeller key is in the shaft and impeller? Is the pickup tube going out of the impeller housing clear of obstructions? How about the screen over the intake, is it nice and clear? How fast does your drill turn it? I would think it needs to turn reasonably fast.
sorry for no better suggestions,
JBJ

 

[Dhadley]

Re: More Johnson Problems

Fill it up to the pump level. It should pull but let's be sure water is at least to the impeller.

If all you changed was the impeller, you might consider a new liner or housing.

 

[samo_ott]

Re: More Johnson Problems

I agree with JBJ, is the drive pin in the impeller to make sure it's turning? To be safe fill the bucket full. the more water the better... it's an easy fix... too much does not hurt anyhting it just spills out a tad... my drill was 330 rpm... how fast was yours? (it's on the side) ... and if all that fails then the housing is probably in rough shape so as the water pressure cant build up... there's very little to go wrong down there... slowly go through all the options and you will find it...

 

[PW2]

Re: More Johnson Problems

I have a 1975 25- not sure if they are the same, but there is a little pin in the drive shaft that drives the impeller--it has to be present.

There is not much else that go wrong down there, that would not be glaringly obvious, at least.

 

[duckhunter55]

Re: More Johnson Problems

Alright fellas after, hearing that the water must be really high i got a bigger tank and tried again. Wala! Water shot out of water tube several inches high. So crossed water pump off my list. Hooked water hose to copper water pipe and stuck inside its hole. Water came out of t stat and water pee hole. So i have come to the conclusion that the past 4 times i have assembled lower unit to motor the water pipe was not in its hole correctly. But i have one last problem. While checking for the water problem i attempted to take water jacket cover off but the very last bolt, i stripped the head. So what do i do now? Water sprays out of water jacket seal at several places nows. Cant replace seals because of the stripped bolt! Thanks for all help!

 

[jbjennings]

Re: More Johnson Problems

Well, Don't feel bad! This is a very common problem and I've done it a few times myself. Sometimes you can get a blow dryer and I've even used a propane torch (making sure that fuel is drained out of motor and FAR AWAY with plugs out) to heat up the area around the bolts so it'll hopefully expand the hole or break corrosion. It's worked a few times. Also, remove the plate if you got all the other bolt holes out and try to get the old screw as flat as possible on the end and then get a GOOD center puch and punch it in the CENTER. Then drill a hole into the screw (slowly, go straight, and don't break your bit) and use a good screw extractor (ease out) and try to extract the screw. Whatever you do, don't even consider using black and decker screw extractors, get the best. When the black and decker (walmart) extractors break off in the hole which I guarantee they will, you'll be "screwed" for sure. I have had luck drilling out the screw with a bit that is a couple of 1/16 ths smaller than the screw, tapping it with the proper tapp and screwing an actual screw in it and then screwing it out. The old threads came out with it and then I cleaned the threads up with a tapp and put the proper screw/bolt back in. You have to REALLY take your time, drill perfectly straight, and be incredibly careful. What you DON"T want to happen is break off a bit in the screw or break off a tapp in it or you are SOL. I hope a couple of real experts like F-R, WBeaton, Sam-OTT, Steelspike, or many other s check in 'cause I'd really like to hear the RIGHT way to do it. I'm just a shade-tree that likes to tinker so take my post from that point of view. Don't worry, it's fixable and after all the work you've done, you'll probably have a really nice motor that you'll always be able to keep in good condition after all the effort to learn about it. Remember, if you break off a high speed bit or screw extractor in the hole, you're in bad shape because they're made of hardened steel and you can't drill 'em out. If you drill out of the old screw into the aluminum case you're screwed, too.
Good luck,
JBJ

 

[jbjennings]

Re: More Johnson Problems

Dang,
I just rechecked your last post and see that your stripped the Head of the bolt. I thought you broke off the bolt! Can you get a hacksaw blade on it and cut a slot for a screwdriver and use the heat to expand the hole or break corrosion?
You may have to take off the powerhead to get to it properly. Don't worry, it's not that big of a deal. But get you some gasket material at an auto parts house so you can cut some gaskets out with a razor blade and scissors to replace the power head base gaskets unless you want to wait for them to be shipped. You can also cut your own exhaust cover gasket, I've done it several times. I like FEL-PRO 1/16 thick material. I don't like the rubberized cork stuff. You can also use a file with the powerhead off to make some new edges on the bolt to get a bite with the proper wrench.
Hope this helps.
JBJ

 

[Solittle]

Re: More Johnson Problems

Do yourself a favor and take it to a machine shop - - they do that stuff for a living.