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flathead.
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July 7, 2015 at 3:20 am #19603
I replaced both the seal under the impeller plate and the seal in the top of the housing. Used 3m 847 for all sealant. I honestly believe this is a problem I created, or with the Johnson lower unit on there. I won’t have a chance to get back to it now until the weekend. I’ll pull it again, clean the water pump housing up. Check the hole behind the water tube receptacle. I do know that was clear, before I put sealant under it. This motor slobbered water like a beast before I switched lower units on it. It has to be something I’ve done since. Maybe I should pull the impeller plate also and clean that up again. I maybe over sealed it. Is it best to seal it around the outside only? I’ll also get a OEM impeller ordered.
July 7, 2015 at 11:57 am #19612Well, I don’t think "oversealing" under the SS impeller plate can really cause any harm. It should be sealed around the outside and around the passage for the water return. Are you sure the impeller hsg screws are seating completely? Might be worth running a tap through the holes. Use a razor blade to scrape/clean the aluminum mating surface under the SS plate, and the 847 between the SS plate and the aluminum gearcase housing.
You shouldn’t need much of any sealer on the gasket between the housing and tube receptacle, especially near that bleed hole, the OMC/merc gasket sealer is probably best in this area.July 12, 2015 at 4:27 pm #19938Ok, back on the lark again this weekend. I pulled the lower unit again. Took impeller housing off, cleaned it all up. Took the plate off, cleaned all sealant off/under that. I used a different plate (used) that was in good shape just in case there was something I was missing there. Resealed the plate down. New impeller. Made sure the hole from case to water tube was clear. It was and still is. Put it back together, no sealant on the impeller housing at all. Double checked all the bolts, they are seated. Fired it up, runs good, thermostat opens, pumps water for approx. 5 minutes, then gradually less water, then none. Same issue, no difference that I can see at all. This motor runs good, I’d sure like to get it pumping water so I can use it.
July 12, 2015 at 4:42 pm #19940Sorry buddy. Same results after a new OEM impeller and checking over water pump parts. I’m trying to remember the story of the impeller housing, I seem to remember that you have tried one from another engine as well.
OK, well how about removing the thermostat cover quickly when it stops pumping water to see if water is still getting pumped up to the cylinder head. I know you said it pumped great before you messed with it, but I’m thinking perhaps there is a head gasket leak, that would explain why it stops pumping water once it heats up. Try a compression test, any signs of water on the plugs?
Post some pictures if you can.July 13, 2015 at 3:50 am #20031I pulled the thermostat cover after it got hot, still water coming up there. I had the same thought about the head gasket so tried to compression test, now it gets really fun. I pulled the plugs. Tested bottom about 105. Went to test the top, it’s a different size. It seems somebody tapped it, then put a sleeve on the plug. It’s not a helicoil, it’s actually on the plug. I’ve not seen that before. The one thing that I have discovered about the water issue today is there was a piece of rubber(impeller I think) in the T stat housing. I didn’t get a chance to drop the lower unit again and see if I smoked the impeller today or if this piece has been in there and just now worked it’s way out. I know it wasn’t there before. So now I need to figure that out next, then figure out how to get the compression tester into the head. Somehow there has to be a way to adapt the threads so I can test the top cylinder. I don’t really think it’s the head gasket, but would be good to know the compression anyhow. Maybe one of you guys will have an idea for that too? There was no water on the plugs.
July 13, 2015 at 9:41 am #20045The insert is simply threaded on the plug when you backed it out. Unthread it from the plug, and thread it into the head.
I lock them in with loc tite to keep that from happening.
I always change the impeller on a new motor to me before I ever try to start it. For that very reason. Is a real pain to dig out old chunks of rubber from the cooling system.
July 13, 2015 at 11:55 am #20047OK, you found impeller chunks in the thermostat housing, do I have it right? Uh oh, if so. Could be that pieces of the impeller are getting stuck occasionally causing the engine to stop pumping/overheat.
The loose spark plug insert could pose a threat for preignition. I am not a fan of spark plug inserts but know I am in the minority on this.
In any event, you need to get whatever insert you plan to use properly seated/locked into the head to avoid a threat of preignition, this engine has relatively high compression.
At this point, I would consider removing the head to find the chunks of impeller that might be plugging up the cooling system, and to get that insert properly installed in the head.July 14, 2015 at 12:28 am #20089Yep, that’s right. chunks of rubber. When it showed up in the thermostat housing, I figured either I found the problem, or smoked the new impeller. Still don’t know which, I have to get a few extra minutes to drop the lower unit. The plug issue isn’t actually an insert, like a helicoil. It’s more like a sleeve that threads on the plug itself. I’ve never seen it before, I’ve seen helicoil but not this. It’s not loose, I tried to get it off. No way. The plug goes in and tightens up just like you would want. Is there an issue using a Johnson 40hp (1960) head? I have one off a 35hp Johnson but it’s been heli-coiled. I think the 40 hp is good, look like it would fit, but would it create any other issues? Thanks for all the help. You guys are a fantastic help to those of us trying to figure these out a little. The collective knowledge on here is amazing. I for one really do appreciate it.
July 14, 2015 at 12:48 am #20093Below the head, above the pleated rubber hose, is a core ("freeze") plug, about the size of a quarter, more or less. Behind that are about five small holes that the water goes through on it’s way out. They may randomly be getting plugged up with those chunks of rubber. At least it is an easier place to begin looking than pulling the head.
July 14, 2015 at 1:37 am #20101As for the plug I have used that solid style insert. You are correct in that it is not like a heli coil that is flexible but is a solid threaded sleeve. This is a type of repair for spark plug holes. Some kits even come with a special tap that starts the same size as the 14mm spark plug the tapers to the oversize thread for the repair sleeve….it eliminates drilling and centers the hole. The insert depending on the type is either made to be preened in (usually has a knurled area under the sp) or loc tited in. They are made in different lengths for heads and can be purchased at advance auto, autozone etc on the tool aisle. I have had one or two stick to the sp and back out.
You can try heating it with a torch if the Lottie is holding it on or just replace it with a new one.
As for the pump issues, sounds like the rubber is something to chase down for sure but if that does not work run it without the t stat installed…..leaving all the stuff under it in place. I actually run my 1958 35 w/o the t stat all the time as I had one of the rare fail closed situations and decided to go without. I am in hot weather and hot water so I really do not run cold, even in the winter. There are arguments on both sides of that issue and I am not wanting to start a debate, but it may help you rule out something in your search. Good luck I love those models.
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