1967 33hp evinrude model 33752c - sloooowwwww!

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Paul Moir

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

I'm afraid it's nothing so simple. The reach on a J6C is the same as the J4C - 0.375". Actually, that's the shortest reach normal plug they sell. I've seen people mistakenly put in NGK B7HS plugs (.472" reach I think) and their gaps didn't close.<br /><br />Is it possible the head has been pulled and shaved down a bit before you got the engine? If it were a bearing problem I would think you'd be hearing a heck of a rattle with the engine running. Ever overrev the engine?
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

no i don't over-rev the engine. I just warm her up gently and then head for the fishin hole. <br /><br />As far as the history of this engine i have little information. it was on a boat that was left out in a yard for 10 years due to a hole in the transome. It had original points, condensors and coils on it when i got a hold of it - the carb had original float - so i don't imagine the engine has had much work. <br /><br />where ya leadin to?<br />-l
 
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Paul Moir

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

Just trying to figure out what would make the piston touch the plug. There's a few possibilities:<br /><br />Over-rev streaches the connecting rod. (unlikely, you would remember and the rod would probably break instead)<br /><br />Foreign substance injestion - top of the piston ought to be beat up. Part would have to come from 'somewhere'<br /><br />Someone shaved the head looking for more power or to remove the warp from a warped head and went overboard. <br /><br />Conrod bearing failure.<br /><br />Carbon build-up (cleared).<br /><br />Next step is to check for play in the con-rod bearings. A simple and effective test is to turn the engine until that piston is at the top (spark plugs out), then turn the engine a bit more until the piston starts to go down again. Then push a clean screwdriver in through the spark plug hole, and see if you can push the piston any further along without the flywheel turning.
 
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Paul Moir

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

Just trying to figure out what would make the piston touch the plug. There's a few possibilities:<br /><br />Over-rev streaches the connecting rod. (unlikely, you would remember and the rod would probably break instead)<br /><br />Foreign substance injestion - top of the piston ought to be beat up. Part would have to come from 'somewhere'<br /><br />Someone shaved the head looking for more power or to remove the warp from a warped head and went overboard. <br /><br />Conrod bearing failure.<br /><br />Carbon build-up (cleared).<br /><br />Next step is to check for play in the con-rod bearings. A simple and effective test is to turn the engine until that piston is at the top (spark plugs out), then turn the engine a bit more until the piston starts to go down again. Then push a clean screwdriver in through the spark plug hole, and see if you can push the piston any further along without the flywheel turning.
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

i'll do that and get back to ya<br />thx
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

I just finishied dinkin with the piston. I found absolutely no play in the piston. It seemed real tight. all movement correlate with motion on the flywheel.I used a small piece of wire to measure the differences in the top and bottom spark holes and the bottome one is about 2-3mm shallower. (that correlates with the beat up sparkplug)<br /><br />the piston wasnt' real beat up at all - it looked to be in the same condition as the other one. (not shiney or increadible smoothe, but not beat up either)<br /><br />I haven't pulled the head tho....yet<br /><br />loupis
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

bummer....<br /><br />i'll get back to ya. Looks like the 5hp seahorse is now the primary.<br /><br />loupis
 
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Paul Moir

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

Could be a case of injestion then. Possible candidates are reed valve nuts (reed will be loose), bits of a conrod or crankshaft bearing coming apart (unlikely), chunk of piston or ring (carbon build up can cause this), carburetor throttle or choke plate screws.<br />A compression test may show a broken ring, but with three in there it may not be obvious.
 
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Paul Moir

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

Yeah. You can have one or two stuck and still get good compression. But if one broke it probably marked up the cylinder wall reducing compression in that cylinder.<br />2-3mm doesn't seem like it would make a difference to me...<br />Hold up there. Is that 2-3mm accurate? I just checked another engine and found that there's only about 4mm between the highest part of the piston top and the electrode of a spark plug on my engine. Can you compare the same on yours?
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

it is real close but not precise. I used a piece of wire in each cylinder and measured the delta of the inside face of the head to the piston.
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

it is real close but not precise. I used a piece of wire in each cylinder and measured the delta of the inside face of the head to the piston.
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

Paul,<br />So i'm ready for the big investigative surgery this weekend. Upon further examination of the head, I discovered another question.<br /><br />The head seems to have a head with a head gasket attached to the block and a head cover with a gasket attached to the head. Do I need to disassemble both the head and the head cover?<br /><br />also, my inspection revealed a black streak down the lower unit - from the block down. It looks like fuel that somehow made it out of the bad cylinder - but not sure. I can post a picture if need be. I wonder if I have some seal problems as well.<br /><br />loupis
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

well, I pulled the head and the lower piston is banged up a bit but i've found no debris floating in the cylinder.<br /><br />the upper cylinder/piston has quite a bit of carbon buildup, but the lower one (the problem child) is shiny clean.<br /><br />not sure where to go from here.
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

Not sure if this is still being monitored, but...<br /><br />I dissasembled the whole block/crankshaft and the problem was 3 broken rings on one piston and 1 on the other. (I think I found my lack of compression!!)<br /><br />The lower piston was tornup pretty bad though the cylinder walls are fine and unpitted. (lucky)<br /><br />I found a couple new pistons from Stone and Sons Marine online so this weekend I'll be putting her back together. Yea!<br /><br />Does anyone have any hints on seating the rings properly upon install of the new pistons?<br /><br />loupis
 
CATransplant

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

You definitely need a ring compressor to get those pistons back in there easily.<br /><br />Don't have one? I've used stainless steel screw-type hose clamps in a pinch to compress rings. Trouble with that is that you have to move it a couple of times.
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

dumb question, but is that a NAPA purchase? How much do they typically cost?<br /><br />loup
 
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Paul Moir

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

There's absolutely no need for a ring compressor for your 33hp. Since there's a little chamfer at the top of the bore, it makes fitting the new rings by hand a breeze. Just squeeze them up one at a time (mind the locating pin!) and push the piston in. I rather do this than risk breaking one with a ring compressor.<br />You can get a 12 point 5/16" socket for the crank bolts from Sears. ;) <br /><br />Since you're fitting new rings, you're going to want to hone out the cylinders before reassmebling. Otherwise the new rings won't seat. You will also gain compression by deglazing the cylinder walls.
 
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loupis

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Re: 1967 33hp evinrude model 33752c - sloooowwwww!

hey guys,<br /><br />good beta on the 12 point 5/16" socket. I picked one up the other day after trying every extra socket I had.<br /><br />What's the scoop on honing the cylinders and deglazing - I'm not real sure on that process. I've been busy with scrubbing off grease and old gaskets.
 
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