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70 Hp Johnson Engine run without oil in fuel

D

davenaus

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"Yes I feel like a A-1 complet

"Yes I feel like a A-1 complete idiot. Bought two new tanks to replace old rusted one. Engine running great on fuel tank #1 with 50:1 oil mix. Switched to fuel tank#2 that contained only unleaded fuel. I had forgot to add the 2 cycle oil. Engine ran at near full power for about 10 minutes then stopped. I realized I had also forgot to open vent in tank #2. Opened vent, primed bulb and engine started. Ran for another couple minutes then stopped. I realized my error with no oil in fuel and switched back to tank #1 with oil. Ran for a couple minutes then stopped and wouldn't restart. Started for a fresh water engine flush 1.5 hours later but sounded a bit funny. Did a compression check on cold engine later in the day. Top cylinder was 30psi with other two at 120psi. Added some 2 stroke oil to top cylinder and checked compression again; it went up to 40psi. I know I need to take apart the heads. I will have to buy a manual to do that or pay a shop $200-300 to do it. The shop guesses $3500-4000 for an overhaul. I can't afford that amount. I have time to work on it. Have been ok mechanically in past. Can't afford rebuilt motor at $5500 or new at $8000. Thinking of selling boat as is. Any kind suggestions?"
 
"Hi Jamie, Thanks for the enco

"Hi Jamie, Thanks for the encouragement. I have enjoyed the motor. Very efficient and good power for my boat. I had another guy on a different forum suggest that I could bore or sleeve the top cylinder as the lower two may be ok. Does that sound feasible? Guess it depends on what I see when I open up the power head. Dave"
 
"Check "Too much smoke&#34

"Check "Too much smoke". We live and learn. Your shop is way too high, where do you live, pal.....Miami?"
 
"Gotta remember that you did n

"Gotta remember that you did not have oil to the crank upper and lower bearings, the center main, or the rod journals.

I did the same thing...had to do all six holes, and all bearings."
 
I have pulled the head. The bo

I have pulled the head. The bottom cylinder feels fine. The middle cylinder is slightly scored. The top cylinder has significant scoring. I am still working on tearing the motor down. Got to 6 bolts holding to lower adaptor. All six had significant rust. I was able to get all but one out. The last one is too rusted for the 1/2 socket. I tried a 12mm which worked on some bolt heads. It won't work on this one. I was also removing the small 3/8" bolts attaching block to exhaust manifold. They both snapped off due to rust. I have two more to remove forward but am uncertain how to get a wrench or socket on them. Ideas welcome.
 
"you can bet its in questionab

"you can bet its in questionable shape to put it mildly. Go on craigslist, or ebay and get another motor. There are plenty of em, and theyre cheap. Take care, Chuck"
 
You can get a factory rebuilt

You can get a factory rebuilt powerhead for $1500-2000. I do not think you will save very much by trying to rebuild it yourself.
 
"I have torn motor down. There

"I have torn motor down. There is some damage to top and middle cylinder walls and pistons. Bearings appear ok but will probably change out both mains to be safe. Have taken to 2 machine shops. They both agree that cylinders should be ok with .03 oversize machining and pistons. Machining cost $250 for all three cylinders. Aftermarket oversize piston kits $130 each x 3 =$390. $390+250 = $640. Gaskets, bearings, etc... take it to $1000. A reconditioned motor is $2500+freight. I am inclined to do the work for various reasons."
 
"I'm not trying to discour

"I'm not trying to discourage you from doing the rebuild. I'm sure it will be a worthwhile project, but I think Doug's comment is worth paying some attention to. You probably need to replace all bearings; possibly even a rod or two. Inspect the crank carefully; there is not any room for imperfection there.

What year engine is it?"
 
"On 8-17, Tim says:
Check &#3

"On 8-17, Tim says:
Check "Too much smoke". We live and learn. Your shop is way too high, where do you live, pal.....Miami?

I sorta agree with him about the costs. I realize you live in Australia, but are the machine costs really double that of those in the States?
I checked around here locally in Florida, and found boring costs to be between $35.00 and $50.00 USD per hole.
Also, ProMarineUSA.com sells piston kits for less than 90.00 USD. I don't know if they ship to Australia.

Are prices really that high down under?"
 
"The engine is a 1980. Shippin

"The engine is a 1980. Shipping to Australia for any kind of weight is expensive. The prices quoted are in Australian Dollars but with exchange at 0.93 let's just say it is the same. The cheaper machine shop was $200 but I wasn't confident he knew what to do having listened to his reluctance. Had some motor rebuild guys look at the crank and they thought it was fine minus replacing bearing. Another issue while I have you here. Attach points for steering are very rusted. Bolts heads are rounds. Rubber is worn but functional. Exposed now but will require drilling out more bolts, more expense, etc... Torn between digging into it and leaving. Friend who knows boats says leave it as it is functional. Getting to them now is easy. Later will require another tear down. Thoughts?"
 
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