1978 4HP cooling questions

[ward cleaver]

4 HP 1978 Evinrude model 4836E

I've had this outboard for a couple of years but have used it only a few times. While running in the tank, I noticed that the pee holes aren't putting out much water. Just spitting instead of squirting. I was going to replace the impeller but it looked new. Stuck a straightened out coat hanger up the tube and didnt find any blockage.

I plan to try blowing some air up the tube to clear out the cooling pathways.

Does the water flow down the tube or up? Where is the other port to the engine?

Any other techniques to clearing out a potential blockage? I've searched on evinrude.com for screens and filters and thermostat but didnt find any.

Makes me wonder if the water flow is sufficient and there really is no problem.

 

[tashasdaddy]

Re: 1978 4HP cooling questions

even though the impeller looks good the take a set, and since the run in an oblong circle, do not keep to the sides of the pump. thus not being efficient. i would say new impeller. water goes up the tube.

 

[DJ]

Re: 1978 4HP cooling questions

I havr also found blockages between the powerhead and the leg. Powerhead removal was needed to clear them but that is surprisingly easy.

Do the impeller first.

 

[ward cleaver]

Re: 1978 4HP cooling questions

Thanks for the info. But I'm having a hard time believing the impeller is bad because it really pushes hard on the inner wall of the cup. So I doubt it is losing a lot, if any, pressure there.

One thing about reassembly, the manual (multi-year multi-model that doesnt specifically address my motor) says to lay down a bead of sealer on the lower unit surface, then slide on the plate. But my water pump assembly has a spacer between the lower unit surface and the cup. And the plate is above the impeller. So I cant see how putting any sealer on the surface of the lower unit would do anything. Putting sealer on the lower surface of the plate would be next to the impeller so that doesnt make sense. Maybe putting sealer above the plate between the housing and the plate is what I need. But I didnt put on any sealer anywhere except the bolts for the lower unit and the water pump housing. Could lack of sealer be a problem?

If you go to the evinrude site with the parts diagrams you can see the layout of the water pump assembly that shows the order of the parts I am talking about. The model number is 4836E.

http://www.evinrude.com/en-US/Accessories/Literature/?popup=true

 

[Vic.S]

Re: 1978 4HP cooling questions

This engine does not have pee hole that puts out a steady sream of water does it? I think you are just looking at the exhaust relief holes that emit exhaust gases plus some water spitting out rather than squirting.


With the lower unit off connect a water supply to the bottom of the water tube and make sure you get a good flow of water coming back down the leg. With some models the grommet at the top of the watertube gets squeezed by corrosion over the top of the top of the tube and cuts off the water flow. I dont know if that happens with this model, or not. If it does you can feel something rubbery at the top with the straightened coat hanger!

I agree with you about the sealant. Your book is not describing your model. I dont think there should be any sealant above the waterpump plate either.

I agree with the others. Its always worth replacing the pump impeller when the lower unit is off.

 

[Chinewalker]

Re: 1978 4HP cooling questions

The holes you are seeing do not squirt out a steady stream, rather a heavy mist. It's an exhaust relief and mixes exhaust and water...
- Scott

 

[ward cleaver]

Re: 1978 4HP cooling questions

I think you are both right about those six holes putting out exhaust gas and spitting water rather than putting out a steady stream like I see on bigger outboards like my 9.8 Merc. I'm starting to think I don't really have a problem with the cooling water flow. There arent any signs of overheating other than what I'm afraid may be low flow.

But out of curiosity more than anything else I think I'll shoot some water up the tube and see how much comes out the leg as Vic suggested. May clear up some blockage if there is any.

 

[samo_ott]

Re: 1978 4HP cooling questions

Touch the head/block when it's running to see how hot it is. If it burns it's too hot. Or splash a few drops of water on it. They should not sizzle off. Or use an infrared thermometer.

 

[DJ]

Re: 1978 4HP cooling questions

Touch the head/block when it's running to see how hot it is. If it burns it's too hot. Or splash a few drops of water on it. They should not sizzle off. Or use an infrared thermometer.

Yes. Those little holes can get stopped up. The true determination is touching the top cylinder head.

 

[HighTrim]

Re: 1978 4HP cooling questions

I have found my infrared thermometer an invaluable tool for the tool box. I use it around the house as well.
Something not exact but similar to this.