Water pump problems on an older Johnson 7.5hp

General Boats and Motors
1

I have a 1983 Johnson 7.5hp that I got from a member on this site for a good price, and the motor is otherwise in good shape.

Recently the tell-tale hole started spitting steamy exhaust (no water, just scalding hot steamy exhaust). It’s obviously overheating. Below is what I’ve done to it. I’m not a mechanic, so any advice you guys can offer me would be a great help.

There seems to be a blockage between the water pump and the engine block. If I remove the thermostat cover and spray water down into it, I get a good steady stream through the tell-tale but NOTHING coming down through the pipe in the lower unit.

If I run the motor in a barrel (for a couple minutes) with the thermostat cover, I get no water flow coming up through the thermostat cover. But if I spray a steady flow INTO the thermostat cover, I get a strong (and very warm) flow of water from the tell-tale. This tells me that there just isn’t water getting to the engine block.

Can anyone suggest a way (other than compressed air and water spray) to dislodge this without having to remove the block? I tried a coat hanger up into the pipe in the lower unit, no luck.

What I’ve done:

  1. I’ve completely rebuilt the water pump twice (first time with used stuff I had that was in very good shape, second time with brand new pump housing kit). No, I didn’t forget the key on the shaft.

  2. Replaced gear case cover and gasket with a good used one from a parts motor (original was cracked and looked like the problem; it wasn’t).

  3. Removed the lower unit and thermostat cover to flush with a jet of water and 120psi air. Did the best I could, no change though.

  4. Gear oil is fresh and not contaminated at all.

Moral judgment under girds the entire structure of laws and is necessary for the rational structure of any significant statute. The idea that our laws can stand independent of moral foundation is senseless.----- Albert Mohler.

2

I found the problem, but the problem got bigger. I pulled the engine block off and accessed the exhaust area, and the rubber retainer that seats between the copper water tube and the block was rotted and plugging the hole 100%.

Unfortunately that’s an obsolete part. Maybe Seaway has it, but it’s obsolete on everyone else’s site.

Anyone ever tear one of these apart? Anyone have any suggestions?

It’s part #69 on this link, for the 7.5hp (they have the 4.5hp model in stock but that won’t work on this motor, looks totally different). http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1983&hp=7.5&model=J8RCTA&manufacturer=Johnson&section=Exhaust+Housing

Moral judgment under girds the entire structure of laws and is necessary for the rational structure of any significant statute. The idea that our laws can stand independent of moral foundation is senseless.----- Albert Mohler.

3

Try shooting a bunch of silicon around it.

ZX

4

Hey Matt, sorry you’re having motor issues, as I’m the seller. If the tube can be rigid, I would glue it in with JB weld or similar. If not, some 3M 5200 sealant, just try to get parts to shiny metal and clean with thinner. Looked at the part, appears to be a quasi seal/retainer.

5

Part shows available from this retailer.
http://www.marineengine.com/newparts/part_details.php?pnum=OMC324604

or this one
http://www.crowleymarine.com/parts/16261.cfm

Iain Pelto
Sea Hunt Triton 160 w/ 90 ETEC “JB3”
Native Manta Ray 14

6
quote:
Originally posted by Rose Ellyn

Hey Matt, sorry you’re having motor issues, as I’m the seller. If the tube can be rigid, I would glue it in with JB weld or similar. If not, some 3M 5200 sealant, just try to get parts to shiny metal and clean with thinner. Looked at the part, appears to be a quasi seal/retainer.

It’s something that you couldn’t have predicted. I’m quite happy with the motor really, never have a problem cranking it and it runs fine.

I have the part ordered. I will try to make it work, if not I’ll try the tips you guys suggested, thanks!

Moral judgment under girds the entire structure of laws and is necessary for the rational structure of any significant statute. The idea that our laws can stand independent of moral foundation is senseless.----- Albert Mohler.

7
quote:
Originally posted by hairball

Part shows available from this retailer.
http://www.marineengine.com/newparts/part_details.php?pnum=OMC324604

or this one
http://www.crowleymarine.com/parts/16261.cfm

Iain Pelto
Sea Hunt Triton 160 w/ 90 ETEC “JB3”
Native Manta Ray 14

Thanks for those links Iain. I did order that part, but I’m somewhat concerned that it won’t work. The original part on this motor was a round grommet, not a U-shape ( have the original with me). There are several other sites that list the U-shape (and part number) that you linked to as fitting only the 4.5hp models. The whole thing is confusing, because I’ve called several places and all of them say (after digging in the computer) that the part you linked to is indeed for the 4.5, and nobody has one for the 7.5

I am hoping that the different shape will still work, meaning they quit using the round one and only use the U-shape. Nobody seems to know.

I do know that I’ve read threads on other forums where this does happen with this motor— corrosion/buildup sets in around this rubber retainer and forces it shut. That’s what happened with this one. The motor was not abused at all, just used and the inevitable happens when it’s used in saltwater.

Moral judgment under girds the entire structure of laws and is necessary for the rational structure of any significant statute. The idea that our laws can stand independent of moral foundation is senseless.----- Albert Mohler.