1963 Johnson Sea Horse 75

The exhaust gasket in the lower unit is bad. Any suggestions to replace besides a complete tear down.

Re: 1963 Johnson Sea Horse 75

Can you please be a little more specific. When you say exhaust gasket, do you mean the exhaust outlet behind the prop or the water discharge exhaust above the water line? Both are easy to access. You won't have to take apart too much.

Re: 1963 Johnson Sea Horse 75

The exhaust Gasket in the mid section, below the water discharge. It seals the lower mid section from the engine. When running I get exhaust in the engine compartment and it chokes out the carb.
With the cover off it runs great. Some say you can seal with silicone but it's too far gone. Tried that.

Re: 1963 Johnson Sea Horse 75

Can you please identify the part number in the following diagram (page 22):

http://www.marineengine.com/parts/vintage-evinrude-johnson/379275/catalog.html?http://www.marineengine.com/parts/vintage-evinrude-johnson/379275/37927500001.htm

Re: 1963 Johnson Sea Horse 75

Page 22, #70, I'm going by what my tech told me.

Re: 1963 Johnson Sea Horse 75

You should be able to inspect the condition of the seal by removing the rear exhaust cover housing (#23, pg 20). If you need to replace the part, it will cost you less than $4 for a replacement. However, you will likely need to remove the front exhaust cover housing (#15, pg 20) as the two housings sandwich around the seal. You will probably need to remove the motor from the boat in order to remove the front housing.

Re: 1963 Johnson Sea Horse 75

IF that part really needs to be replaced it is quite a job. The powerhead has to come off, the lower unit has to come off, then the midsection has to come out of the outer "shell". Then the powerhead adapter plate has to be removed. Only Now, can you replace that rubber donut seal. It has to go over the top end of the exhaust housing. Yeah, I know, it looks like it would go over the bottom end, but it won't.

BUT before you get into all that, you had better make sure that is your real problem. Let me ask you one simple question: Does the smothering take place with the motor on a boat, on the lake, and at higher speeds? If it does, the donut is not the cause. Reason? Because the exhaust is buried in the wake far behind the boat and is not bubbling up around the shaft.

It could be the cause if the problem is only manifested with the motor on a boat, on the lake, and idleing in neutral at the dockside. Reason? The exhaust is bubling up around the shaft and being drawn up into the hood/carburetor.

A third possible scenario is are you running the motor in a tank of some sort? Forget it. Even a new motor wouldn't run in a tank with the hood on.

OK, bottom line: There is another, more common cause of the smothering problem. There is a foam rubber seal on top of the water pump housing. If that foam seal is shot or missing, it will smother out the carburetor, big time. Check that seal on the water pump before going any further!!!!

Re: 1963 Johnson Sea Horse 75

Thanks for the experienced advice F_R. I have never changed that seal. Only seen it when I have had the rear-exhaust cover off.

Re: 1963 Johnson Sea Horse 75

Great advise. The problem is only at idling. When I give it the gas she goes. If I take the cover off and a little wind then she will Idle.
Before I start a disassembly I will check the rubber seal on the water pump.
Any suggestions who has parts?

Re: 1963 Johnson Sea Horse 75

Hope that it is not that larger exhaust seal. I've atttached a pic of what it looks like new. The problem is that it has been NLA since sometime in the 1980s. Since they are made of rubber and the NOS seals that you find are more than 30 years old, they break very easily when you try to install them around the top end of the exhaust tube. I have basically the same motor as you and I recently replaced my seal. I had my motor completely disassembled for a rebuild so it wasn't too big of a deal to replace that seal. But, I had to buy 3 of those seals before I got one into place without breaking. The pic is a new seal that broke while trying to put into place. As F_R says, if you don't have your motor disassembled yet, you will have to get it completely disassembled. A lot of work.

I thought about some homemade solutions but since I found NOS parts, I didn't need to use the homemade ideas. For instance, once you remove the rear cover, you have access to the top of the seal all the way around to the front. You *could* spray some of that foam-in-a-can with a hose attachment onto the top of the seal all the way around the exhaust tube. I believe that one brand is Great Stuff. This is what I was going to try if I couldn't find the seal anywhere. I don't know if it would have worked though. Hopefully, it is the small donut seal on the water pump that you need to replace and none of this stuff will matter.

Re: 1963 Johnson Sea Horse 75

Thank you for the advise. I need to know where I can purchase these parts. The seal and water pump seal. Could you give me the part numbers? I was also thinking pumping urethane over the old seal first and if that got me thru the summer then this winter fix it correctly. First I'll try the water pump then go from there. What parts do I need to do the water pump?

Re: 1963 Johnson Sea Horse 75

Have you ever had the water pump impeller replaced? Did the previous owner have it replaced recently? If not, you should buy a water pump kit and replace the impeller. You can find them here at iboats. You can search the parts pages to find the kit that you need. You should also call them and ask whether their kit includes the foam rubber ring that F_R was talking about. It is part #2 on page #18 of that link above. If not, you'll need to get it. You should also have a Factory Service Manual from OMC. The FSM is available at outboardbooks.com. Pays for itself with the first repair.

Re: 1963 Johnson Sea Horse 75

Thanks, Will do. Let you all know what I come up with.

Re: 1963 Johnson Sea Horse 75

Do you have a part number for this seal? Is it 305314

Re: 1963 Johnson Sea Horse 75

EdsBoat, if you go to the page following the exploded diagram in the link above, you will see the list of part numbers and descriptions.

It's part #305762 and can be purchased here at iboats: http://www.iboats.com/Gearcase-Cove...8136959--**********.141116140--view_id.173937

Re: 1963 Johnson Sea Horse 75

I think the part your talking about is the seal for the water pump. I'm talking about the exhaust seal. I replaced the water pump seal and sealed the exhaust seal then ran the boat. Great for 2 hours but did not charged the battery. I replaced the voltage regulator but have not test run the boat. Hope to this weekend. I'm getting parts together for a future rebuild. I know I will need that exhaust seal. V4A-V4AL-15E Parts catalog I think it it's part number 305314?

Re: 1963 Johnson Sea Horse 75

Yes, #305314.

Re: 1963 Johnson Sea Horse 75

Thank You.

Re: 1963 Johnson Sea Horse 75

This problem is on the back burner for now. Trying to fix an electrical issue.