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foxstan,

You make a good argument. Thank you for your thoughtful response. I'm in a bit of a quandary. I may have just stumbled onto a winter time project!

Regards,

Tom
 
I already told you to replace the exhaust gaskets. If you want to try getting by without doing that, your choice. But when you have the exhaust cover off, you will be able to see if the piston skirts are scored and/or rings stuck. If it looks good, put it back together with new gaskets and run it. One other thing you mentioned was bearings. Those never are bad unless it is a total disaster, like rust or breakage.
 
fdrgator,

The bottom piston was scored as viewed from both the exhaust ports and the intake ports. I dismantled the powerhead. Everything looked good except the bottom piston. I used a cylinder hone and cross hatched both cylinders. All parts measured OK. Based on the sound advice that I received from you and others, I ordered one piston, two sets of rings and a powerhead seal kit. The parts came in today. The piston had the right part number but the top ring groove was wrong. The groove was not parallel sided. The top of the top ring groove was at about a 30 degree angle (the groove was narrower at the bottom than at the top). The top ring would not fit. I contacted the parts supplier. They are looking into the issue.

As soon as I get the correct piston, I will reassemble the power head. I scrubbed and oiled the crankcase after honing the cylinder. All other parts have been cleaned and oiled, awaiting reassembly.

Thanks for your help.

Tom
 
I am glad that you took a look. I hope the engine give you years of trouble free service when you get it back together and running!
 
foxstan,

The internals look great, except for the bottom piston. I'm pleased with the progress to date. The outboard was purchased new in 1971 by my Papa. I'm 69 and am in love with nostalgia. At this point, the goal is not economy but preservation. I'll get it back in top shape and will leave it to one of my sons. That's the plan. You guys have helped me an awful lot and for that I am thankful.

A few hours ago I got word that a replacement piston is on the way!

Tom
 
kimcrwbri,

This will be the first time I have assembled a split crankcase. I have practiced assembly several times without the O-ring on the outer race of the top and bottom bearings. I think I can manage. I was planning on using the Permatex Aviation Form-A Gasket Sealant on the joint between the two halves of the crankcase and on all gaskets that require sealant, such as the exhaust cover gaskets. Will that sealant do the job or should I use something else?

I will check the end play on the crankshaft. My information calls for 0.009" to 0.023". That's what I'm shooting for. I plan to check that before installing the carbon seal and spring assembly on the bottom of the crankshaft.

Thanks,

Tom
 
kimcrwbr1,

Thanks for the link to the thread. Based on that information, I will use Loctite 518 to seal the crankcase. In an earlier posting, I believe you suggested Permatex Aviation Form-A Gasket Sealant for gaskets that require sealant. Is this an acceptable sealant for the exhaust cover and the bypass cover gaskets?

Thanks,

Tom
 
I have rebuilt the powerhead and am ready to bolt it to the exhaust housing. The gasket that I have is tacky on both surfaces. Should I install it as-is or should I apply aviation sealant to the gasket?

Thanks,

Tom
 
To One and All:

Thanks to all of the folks who helped me with this project - it's done! I started the motor in a barrel this morning. She runs great! No leaks, no problems, and plenty of water coming from the exhaust. The engine runs smooth. I made a spark tester. I have a sharp, blue spark from each plug wire across a 5/16" gap. After about 20 minutes at idle in the barrel, I checked the compression. The bottom cylinder was 120 psi and the top one was 115 psi. The bottom piston is new and both sets of rings are new.

During the overhaul, I replaced the water pump impeller, the thermostat, I cross hatched both cylinders with a new cylinder hone and plenty of oil, replaced the bottom piston, both sets of rings and all gaskets and seals. At this point, I am pleased with the job. The motor starts with a very short tug on the rope and runs really smooth.

Thanks again for all the help. WE ended up with a successful overhaul.

Tom
 
Need to research he impeller you originally purchased as if its a serria aftermarket and it failed as you posted,they will pay you for the parts used in in repair.,...they had a problem with the hub failing. The paid for several v-6 rebuilds....
 
faztbullet,

The impeller that failed was OEM, Johnson. I bought it from marineengine.com. I discarded it. I sent it to the trash the day I finished the rebuild. I had no idea that I could recoup any of the cost associated with the rebuild. It did fail just as I described. The rubber separated from the hub. The whole affair was an expensive lesson.

Thanks,

Tom
 
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