1955 Johnson RD-17S 25hp Restoration

[HighTrim]

Re: 1955 Johnson RD-17S 25hp Restoration

I have never tried a micro torch but cant hurt to try. Heat the general area. It will all quickly become hot anyways. I like to then hit it with a `Cold` aerosol can, and then penetrating oil. Or use compessed air in a can upside down which accomplishes the same thing. Or if cold out bring it outside to cool. Then heat again and try again.

Sometimes, overtightening it a little, then trying to back it out again will do the trick! Just be patient. Easier than trying to drill out the broken bolt. Not too bad if it breaks with some sticking out of the block, so you can get vice grips on it, but if it breaks inside it becomes more of a pain.

 

[jb93]

Re: 1955 Johnson RD-17S 25hp Restoration

I have never tried a micro torch but cant hurt to try. Heat the general area. It will all quickly become hot anyways. I like to then hit it with a `Cold` aerosol can, and then penetrating oil. Or use compessed air in a can upside down which accomplishes the same thing. Or if cold out bring it outside to cool. Then heat again and try again.

Sometimes, overtightening it a little, then trying to back it out again will do the trick! Just be patient. Easier than trying to drill out the broken bolt. Not too bad if it breaks with some sticking out of the block, so you can get vice grips on it, but if it breaks inside it becomes more of a pain.

Did 3 hot then cold cycles with propane torch and upside down compressed air. Then heated bolt head with direct flame for one minute then moved to side of block where threads are and heated with direct flame one minute. My philosophy was block would be expanding while the bolt cooled off. I got it to turn loose 1/8 of a turn and then just went back and forth between loosening and tightening each time loosening a little further till it became easier to turn.

Summary - I'm coachable. Thanks Chris!

 

[HighTrim]

Re: 1955 Johnson RD-17S 25hp Restoration

Awesome. Victory for you although drilling out a broken head bolt can make for an interesting afternoon

 

[jb93]

Re: 1955 Johnson RD-17S 25hp Restoration

When I had the head pulled, I tilted the motor up and put some Seafoam in each cylinder. It drained past the piston rings overnight. I also cleaned all the carbon off the top of the pistons. Installed new head gasket. Opened bypass covers and decarboned them. Rings look in good shape. Reinstalled with new bypass gaskets.

I decided to retest compression after replacing the head gasket. I get 88/90 on both cylinders. This seems little low, but they are even. Should I proceed without worrying too much about the compression or do I need to consider gauging bores, re-ring job, etc? I don't want to do more than I need to if it isn't necessary.

 

[Vintage Boat Guy]

Re: 1955 Johnson RD-17S 25hp Restoration

I've been told if you find an outboard with bad compression, leave it and find another unless it has sentimental value

 

[HighTrim]

Re: 1955 Johnson RD-17S 25hp Restoration

All gauges read differently, the only thing surprising is that you lost compression. Was this with the same gauge? How square was the head when you dressed it? The main thing is that you have even compression. I would continue and perhaps decarb once done with Seafoam. there is a thread in the Top Secret Files about this.

That is probably good advice VBG, but Im stupid and would never leave a poor motor for the scrappers.

 

[nwcove]

Re: 1955 Johnson RD-17S 25hp Restoration

I've been told if you find an outboard with bad compression, leave it and find another unless it has sentimental value

i agree and disagree.....its just a shame to see so many of the oldies end up in the recycle bin, when they could be cheaply brought back for another 50 years of service. and its even worse when they end up going for scrap, when theres someone out there that would love to have a donor. jmo

 

[jb93]

Re: 1955 Johnson RD-17S 25hp Restoration

All gauges read differently, the only thing surprising is that you lost compression. Was this with the same gauge? How square was the head when you dressed it? The main thing is that you have even compression. I would continue and perhaps decarb once done with Seafoam. there is a thread in the Top Secret Files about this.

That is probably good advice VBG, but Im stupid and would never leave a poor motor for the scrappers.

The first check before I bought it was a rental gauge from auto parts store...read 100/90. My gauge (after dressing head and replacing head gasket) reads 88/88.

I am up for gauging the bores and having it honed with new rings if the bores and pistons are in spec. I will already have it torn down for repainting, except I wasn't planning on removing the block. I could go ahead with that and replace the upper/lower seals while I am at it.

FYI my 1957 Fastwin gauges 100/100 with the same compression gauge, so I don't think my gauge is reading low.

Should I go for the hone/re-ring or just let it be with the slightly low but even compression I've got?

 

[HighTrim]

Re: 1955 Johnson RD-17S 25hp Restoration

That will have to be a judgement call on your part.

I don't see any mention still about dressing the head, like the directions I posted, did you do that?

Sometimes, usually the compression increases after running them for a while after they have been sitting. Especially if SeaFoam is used. The way you used it doesn't really do much, it need to be injected under combustion to work properly. You will be able to tell because your motor will smoke like a locomotive!

 

[jb93]

Re: 1955 Johnson RD-17S 25hp Restoration

That will have to be a judgement call on your part.

I don't see any mention still about dressing the head, like the directions I posted, did you do that?

Sometimes, usually the compression increases after running them for a while after they have been sitting. Especially if SeaFoam is used. The way you used it doesn't really do much, it need to be injected under combustion to work properly. You will be able to tell because your motor will smoke like a locomotive!

I dressed the head per the way you posted, except not emery cloth. Used 150 grit paper followed by 230 grit paper on glass top surface until all areas of the head appeared to have been polished. I checked it with a metal ruler and a spot light and I did not see any light peeking through checking several locations in various orientations. I think it is flat?

I understand what you mean on the seafoam. I basically just used it to remove the carbon on the tops of the pistons and it drained past the piston rings. The rings are clean and I believe free in looking at them after removing the bypass covers.

Since compression is even, I'm gonna continue and run the seafoam procedure then see where I end up.

 

[Chinewalker]

Re: 1955 Johnson RD-17S 25hp Restoration

Any evidence of an overheat in its past? Paint discoloration on the cylinder head, compared to the rest of the block? A good overheat can take some of the temper out of the rings, reducing compression.

 

[jb93]

Re: 1955 Johnson RD-17S 25hp Restoration

Any evidence of an overheat in its past? Paint discoloration on the cylinder head, compared to the rest of the block? A good overheat can take some of the temper out of the rings, reducing compression.

The head paint looks same as rest of block. The only thing noted was that paint right at the mating surfaces of head and block had debonded and I could scrape it off with a brass wire brush. I just view that as old paint debonding...no other evidence of paint discoloration.

 

[jb93]

Re: 1955 Johnson RD-17S 25hp Restoration

I have cleaned and rebuilt carb. Check link/sync. Here is a picture of where cam is in relation to roller when the butterfly starts to open. In my service manual it appears it wants the mark on the cam to be lined up with the "pointer" just to the left of the roller. It starts to open on the left edge of the "pointer", which I have marked with a red line...so not the center of the pointer but on it. The way I determined opening was by putting a twist tie on the butterfly linkage and having it point up to give me a visual aid. As soon as it started to move the twist tie visibly I stopped. Is this opening just a tad too soon or good shape?

 

[HighTrim]

Re: 1955 Johnson RD-17S 25hp Restoration

Seems pretty close. You can pull the cam out a touch to get the mark on the cam to be aligned with the pointer when the butterfly moves. Good for you for reading the manual! lol

A lot of guys set it with the roller like you would on other motors. They don't even know about the pointer.

 

[jb93]

Re: 1955 Johnson RD-17S 25hp Restoration

Seems pretty close. You can pull the cam out a touch to get the mark on the cam to be aligned with the pointer when the butterfly moves. Good for you for reading the manual! lol

A lot of guys set it with the roller like you would on other motors. They don't even know about the pointer.

Flashes of intelligence. Not very many, but every once in a while.

 

[jb93]

Re: 1955 Johnson RD-17S 25hp Restoration

I tore the motor down all the way and had all the parts soda blasted. I removed the exhaust plate and the block was full of unburnt oil. I removed 90% of it by scraping it out and using some seafoam spray, so it is clean now. It is one more big (to me) step to split the motor to replace upper and lower crank seals and probably go ahead and have cyliders checked for spec and hone/re-ring if good. Should I go to this much effort?

 

[racerone]

Re: 1955 Johnson RD-17S 25hp Restoration

On an older motor like that you should tear it all apart. Inspect everything and re-assemble.-----There is usually something wrong inside these things that needs attention.

 

[Vintin]

Re: 1955 Johnson RD-17S 25hp Restoration

I read in the manual that the spark advance spring #304220 should be replaced with the stiffer #304656 spark advance spring in my 1957 35hp Johnson. I don't remember if that applied to the 1955 25hp Johnson or not.

 

[jb93]

Re: 1955 Johnson RD-17S 25hp Restoration

Lots of parts in primer waiting for a few more to be completed so I can spray color soon. I had Sherwin Williams color match Seahorse Green. They got it bang on except the factory color has some metallic in it that the base color of the SW paint doesn't. I can live with that for the price vs my intended usage. It is the same type alkyd enamel that hardener can be added to. Anyway, here are some of my parts in primer on the master bath counter...my side. My wife is so patient. Saint she is.




Here is one of the two repainted pressure tanks in Rustoleum smoke gray and gloss black. Used Tractor Supply hardener and sprayed with Preval bottle sprayers from Lowes or HD. I went gray instead of the OMC red/orange because I already had the paint and I'm not necessarily going for period pure. I probably won't put decals on them. Hopefully this isn't full on blasphemy.

 

[jb93]

Re: 1955 Johnson RD-17S 25hp Restoration

How do you guys clean up the powerhead for painting? The cylinder cover is installed with new gasket, but everything else is stripped off of it including flywheel and armature plate. I'd thinking of cleaning it up with degreaser (maybe TSP) and toothbrush? then use some wet sandpaper...maybe 220/300 to wet sand all the nooks and crannies best I can then clean again...dry, prime and paint. Make sense? Will this work?