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1972 Johnson 65hp carburetor location

mtmech

New member
Hello everyone :cool:
Very nice forum you guys have going here, full of everything we need and lacking all we can live without.

Last year about this time I bought a 1967 Fiberform Olympic V runabout that had been sitting since 1993, and needless to say it was in sad shape, but had a solid skin on it and looked sleek in my eyes.
Since then I've replaced every piece of wood in the lower hull. Stringer, floor boards, transom. All of which are now fully inundated with epoxy resin and completely covered with one or more layers of fiberglass. After all that I decided on a nice dark brown base for the top, with large red metalflake and a super clear 6 coats of 2k urethane over it all. It gives it that "wicked witch of the west ruby slipper" look ;). I don't really like the flexibility of the urethane for a top-side coating, and in hindsight I should have done gelcoat instead. If i set my beer on it, it gets scratched far too easily :eek:. I was told the UV resistance of urethane was/is far greater than that of any gelcoat, but we shall see.

I got her out on the water on friday for the second time since I bought it, I had her out once before right after the purchase and was afraid the transom would break, not to mention the floor moving up and down under my feet. It runs a little rough from idle to midrange, but starts right up every time and really screams at top end. I know for sure I need to disassemble, inspect, and clean the carbs. I have done setting the timing and synching the ignition to throttle, and tried to get the low speed screws set. The adjustment didn't seem to help on 2 of the carbs, I suspect there's some solidified fuel/oil restricting things in there. I was looking at the carbs while having a brew and noticed they have casting numbers on the starboard side of the assembly, the upper and center being 315082 - D4 and the lower being 315082 - D2. This seems odd, seeing as how most of the center carburetor parts have different numbers in the parts diagrams, so I would expect the center one to have the different casting/part number. The motor has obviously been apart before, right down to the crankshaft, because there are 2 different types of sealant at just about every seam.

Do any of you fine fellows have one that hasn't been apart (or hasn't been put back together in a possible wrong configuration) that you can look at and let me know if this is indeed the right or wrong configuration? Or maybe even one of you has been there and found the carbs in the wrong place on his engine.

I checked online and in forums, but the closest I could come to any answer was that one number was upper and one was lower on a 50hp Johnson.

Thank you, and sorry for the long-winded post.
~Eric
 
I have the exact same engine on my 72 Starcraft Jupiter. I have also had the exact same problem that you're having. You have one or two cylinders that aren't firing right because of the jet. I was able to identify the issue by pulling the plugs after I ran it for awhile. My two and three were both running lean. Fattened them up and it ran like a top until this weekend when the fuel pump went out.

I'll check my motor in he AM and get back to you to answer your question.
 
Thanks for your input kimcrwbr1, I will check that when I have them disassembled for cleaning and any repair they may need. The engine was sold to the PO at this altitude. I'm not sure if the dealer had the insight to sell it with the right jets or not. What I was wondering more was, since the last person that had them off put a few things in the wrong places, did they place the carbs in the wrong places also. (they had the throttle/timing stop screw bracket bolted two holes up on the crankcase, so it was doing nothing, and many other things adjusted improperly, like the timing pointer and throttle linkages, for instance). From what I've seen so far I was surprised there wasn't more issues. I noticed the engine was running rather cool last weekend, so today I pulled the thermostat and found it stuck 1/4 open or so. I'll be replacing that along with completely disassembling the carbs and thoroughly cleaning them (and checking jet sizes as you suggested). 3820 feet in elevation.
 
Well, I pulled the carbs yesterday and went through them after checking the compression cold (95, 100, 95). I felt this was a little low, even cold. Anyone got an opinion? I'll check it at normal operating temp later. The PO (or his mechanic) scribed numbers in the carbs before he removed them and I noticed no difference in the D4 and D2. They were as clean as a whistle, maybe a bit more sanitary. One high jet was a bit messed up, but I deepened the slot a little, cleaned up the threads at the slotted end, and all is well. I made the jet tool out of 3/16" (i think) stainless rod I had laying around. Beat the tip to widen it, ground both sides to make a screwdriver shape, and rounded it off to fit in the 1/4" threads nice and snug.
When I was pulling it apart the first thing I noticed was that the #3 throttle plate wasn't completely shut at idle. Today when I was running it with muffs just that small adjustment seemed to make a huge difference, and I got it hitting on all 3 quite nicely. It seems to want to run with the idle screws about a half a turn out. I'm sure in the water it will need to be a bit richer - I was just playing with adjustment on muffs, no load, not in gear, for ****s and giggles.
Today i replaced the thermostat with a OEM one ( plastic? ffs :O ). Nice 135 steady temp with muffs.
 
Sorry I never got back to you. Got a little tied up with mine. The middle carb is the one that is different. The only difference between it and the other two is that it receives fuel from the pump and distributes it to the other two. Otherwise the carbs are interchangeable.

Mine runs cold comp at about 130-138 psi. My head gasket is only about five months old though. I blew out the #1 cylinder in December.
 
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