1989 4hp Evinrude not pumping much water

[SuB8HaVeN]

I just recently bought a few older OMC outboards and also ended up with this 1989 Evinrude 4hp that's in cherry condition. This is the deluxe model with the full gearcase. It's got very low hours on it and the carburetor and fuel pump even have the original gaskets, never gone through. No corrosion at all, etc. I got it running in the tank and it runs smooth as could be. The only problem I found was that it didn't seem to pump much water. So I went down to the local OMC dealer and bought the water pump repair kit and replaced the impeller. The original impeller was a 3 blade but was in good condition, so I replaced with the new impeller anyways while I had it apart. Lower unit was excellent, no corrosion. After replacing the impeller and gaskets, etc, it still wasn't pumping much water. It is spitting out water out of the row of exhaust holes, and at idle it trickles out of the upper water outlet. Running in the tank for about 10 minutes the powerhead warms up, but it's not too hot to touch. I had a later 6hp Evinrude at one time that seemed to pump more water, but as far as I can tell this seems to be normal. I just want to make sure before I put her on the boat and burn it up. Does anyone have any experience with this particular model and how much water it should be pumping through it?

 

[TOPPER14FISHERMAN]

Re: 1989 4hp Evinrude not pumping much water

I've got the same problem with my 82 evi 7.5 hp motor. Everything looks good. It runs good on the tub just not much water spitting out. I dont have the answer, i'm just gonna watch your post too. Thanks, keith

 

[Vic.S]

Re: 1989 4hp Evinrude not pumping much water

The 4hp does not have a telltale as such, unlike the 6hp, so you won't seen the strong pee stream that you did from the telltale of the 6 hp.

The cylinder head will get pretty hot around the plugs and the exhaust manifold cover will get hot because it is not water cooled but apart from those places if you can touch and maintain contact for a few seconds it's OK.

If you cannot touch or if you see steam from the outlet on the leg you have cooling problems.

 

[Vic.S]

Re: 1989 4hp Evinrude not pumping much water

The '82 7.5 has a telltale , it also has a pressurised cooling systyem. You should therefore have a powerful jet of water from the telltale.

If that is not the case first check that the telltale is not restricted.

If genuinely a poor flow then pump is suspect but the grommet at the top of the water tube can block off the flow. Always check that you can get a good flow of water through from a hose while doing the pump. Also push a stout wire up the water tube. If it hits something solid at the top that's good but if it hits something squidgy that's the grommet and it is in need of replacement. unfortunately the power head has to come off to do it .. That grommet is a real PITA

Same thing as posted for the 4 Hp . If you can touch and maintain contact for a few seconds its Ok ( the exhaust manifold cover is water cooled on these too so that should be coolish as well)

If you start seeing steam from the exhaust relief port. You have cooling problems.

 

[SolingSailor]

Re: 1989 4hp Evinrude not pumping much water

I have been running a 1988 4 HP since new. It only "spits" water out of the exhaust relief holes. At low idle, a trickle of water running down the leg is normal.

I have checked temps on my engine with an IR reader, and a temp crayon.

I don't think you have any problem with your water pump.

Of course, when in doubt, change the impeller. Mine is a three-vane.

 

[SuB8HaVeN]

Re: 1989 4hp Evinrude not pumping much water

Well thanks then, that's quite a relief. OMC has been changing up their water pump kits a lot. When I was at my local dealer they said the part numbers had all changed. The new impeller kit came with a 5- or 6-vane impeller, I forget exactly. I also have a 1976 6hp Johnson that I bought a kit for, and the new impeller kit has a plastic housing (original is metal) and smaller impeller. I opted to clean out the existing impeller and reinstall the old one since it was in good shape. I'd have a hard time replacing the impeller with this new kit that has one about half the size. I guess they're just trying to combine the kits to make them more universal so that it's easier to stock them.

That's a good suggestion for clearing out the telltale, though. I had a bigger Yamaha (this one taught me to not buy non-OMC outboards) that had seen quite some salt water and the tube was plugged up. I straightened a paper clip and forced it up in there and a bunch of crud came pouring out and the flow opened up.

 

[TOPPER14FISHERMAN]

Re: 1989 4hp Evinrude not pumping much water

Thanks Vic.s . thats very good info on the 7.5 evi. I know the grommet at the impeller housing is good but didn't know there was amother at the top of the tube. Now I have more ammo for my battle this evening when I get home. I WILL get this 7.5 riverworthy!! So far, I've rebuilt the carb and changed to new plugs and the motor runs awesome --tonight I'm gonna try the wire deal. Thanks again, Keith.

 

[TOPPER14FISHERMAN]

Re: 1989 4hp Evinrude not pumping much water

Vic.s , working on my 7.5 evi last night . checked the thermostat, and there is not one...just the gasket and cover. You mentioned that my motor has a pressurized cooling system. I live in sunny south GA so is the thermostat really neccesary for the engine to pee properly? Also, I accidently broke the plastic fitting that the pee tube connects to at the block (it was pretty swolen and constricted as if it had gotten too hot ). After digging out ALL the plastic from the threads, I was able to replace it with a brass one. My main question, Will the engine still be ok without the thermostat in warm weather? Thanks , Keith

 

[Vic.S]

Re: 1989 4hp Evinrude not pumping much water

Without a thermostat the engine will not operate at the temperature it is designed to. The thermostat also functions as the pressure control valve so the system will not be pressurised without it and a you will therefore probably not have such a powerful stream from the tell tale.
The diagram below shows the thermostat etc and the spring that controls the pressure. #22 is the thermostat.

Brass as a fitting may cause galvanic corrosion of the aluminum. Perhaps i would not worry too much in fresh water but I would prefer not to use brass in contact with aluminum in seawater

DIAGRAM

 

[TOPPER14FISHERMAN]

Re: 1989 4hp Evinrude not pumping much water

Thanks for the help, Keith