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1985 70 rebuild

E

edac

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The last time I was out fishing on the Mississippi, my engine developed a knock.
I pulled and disassembled the power head, everything looks great. Slight discoloration on the connecting rods, and a little carbon on the top of the pistons.
My question is, what do I seal the two halves of the "cylinder block/crankcase assembly" with? There is no gasket or "O" ring. I have some Loctite 515 gasket eliminator that I've used on centrifugal chillers in the past. Will this do the job?
I've also used high vacuum grease on "O" rings in the past, A silicone based lubricant to extend "O" ring and oil seal life. Is there any reason not to use this? Would it help in the labyrinth seals between cylinders?
I picked up a gasket set here (P/N 0439084)
I'll be pulling the lower end and checking the gearcase soon.
I wanna get this back together and running before the Ohio Walleye run in April.
 
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By the way, compression in cyl 1 138, cyl 2 141, cyl 3 140.
before and after pics from 2 years ago.
KIMG0407.JPGKIMG0406.JPG
 
Sounds like it might be a lower unit issue.----The oil mixed with gas does a wonderful job in those labyrinth seals.----No grease needed at all.----The 515 works.----Most of the sealer should squeeze out of the joint.----This is a precision joint.-----Metal to metal joint for proper bearing " clamp up" on these 2 strokes.
 
Remember....that dowel pin is directional, eh? Just like some float pivot pins, and watch band pins.
Knock? Flywheel rubbing? Did you hit anything? Lower unit lube clean?
 
Yes, I've dealt with alignment pins before. The boat is in Indiana for the winter, I'll be going through the gear case soon. I found a 87 with a bad cylinder coming in a couple of weeks as a parts doaner. Can't wait to get rid of the pilot orifice in these carbs. I do believe the 85 was the only year that they used a pilot orifice in the carbs.
The knock was intermittent, and now that I thought about it, it's probably gonna need some teeth on the gears!
I've been using this motor for over 30 years, so new seals and reeds are probably over due.
I'll keep you posted. And thank you so much for the words of wisdom. As I go forth in these unfamiliar waters, I'm moving slow, and words of wisdom go a long way.
I the other hand, I miss my apprentice. Anyone want to scrape gaskets off?
 
I believe the 87 model 70 HP is the 56 cubic inch block.----A different motor displacement than your 85 model.----Totally different casting for the block.
 
So I got everything back together, except the exhaust manifold. "Marineengine.com parts" seems to have a problem with the crankcase to exhaust manifold plate gasket. The gasket kit was sent with two exhaust manifold gaskets, which are needed for the manifold and cover. It did not include the third one needed for the crankcase to exhaust manifold plate. I ordered one separately, part#317228, gasket #331916. This is the same as the one above. But it seems to be the wrong gasket. It would allow cooling water to enter the exhaust ports on the crankcase. Can someone chime in and let me know if my thinking is correct?
in the parts explosion for this motor it shows the correct gasket and manifold, but under the parts list, the gasket doesn't match the picture, and the manifold is the exhaust housing adapter from the mid section.
 
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Yes, teeth are hard to replace!
Doaner motor got sold to someone else, :(
Looks like the pinion bearing lost a needle and chewed up the gears. Or the chewed up gears caused the bearing failure.
Searching for parts, lower, or new motor now.
 
They made that lower unit from about 79 to 88 and only on the 3 cylinder motors.------Should be lots of good used ones around.----Your location ?
 
Beautiful....shaft bearing surfaces look nice. Get your parts list together and call Tim's Outboard in Hackensack MN 2186822331. Rebuild it yourself....WAY better than a used one. Talk to Cassie or Theresa, Mike or Dan may be able to round up select parts immediately.
 
Pinion and forward gears are almost $400. A couple of $25 bearings, with a gasket or two, would have me in over $500.
the gear housing took quite a hammering from that needle floating around in there. But everything moves and rotates as it should.
Wish I got that $200 doaner motor.
I'll get a parts quote from Tim's, Walleye run in Ohio is just a few weeks away!
 
A new pinion gear needs to be put in the proper position.-----Shims needs to be determined or gears will not last.
 
racerone said:
A new pinion gear needs to be put in the proper position.-----Shims needs to be determined or gears will not last.
Click to expand...

My Clymer manual goes over gear shimming with the shim gauge part#320739. Is this available? Is there a different procedure?
 
Just an update.
Got my new gearset, bearings, impeller, and seal kit. Assembled gearset with blueing on them to see the pattern. Everything looked good, riding in the center, not too deep. reassembled the lower unit. Shift rod "o" rings were the hardest part.
Will be putting it back on the motor later this week, and hope to be testing it on the water next week.
Thank you again for all your insight and encouragement, I wouldn't have done it without you.
 
All back together! Test ran it on the driveway with the muffs. Started good, idled smooth, throttled up nicely, shifted like it was supposed to.
Hoping to put it in the water tonight or tomorrow, depending on the rain.
Thanks again for the help and encouragement!
 
Ended up using Gear Pros, quick and reasonable price.
Now if the rain lets up, I'll be able to test it out on the water.
Hoping the boat smells like Walleye next week!
 
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