1965 18HP Johnson outboard

[EZ]

Trying to tune this motor for top end performace and have some questions,set the points at .020, used Sea Foam in the carb.Checked the plugs found RJ19LM in the motor, one dealer say's they are correct another one say's no should have J8C, which one is correct,put a photo-tach and timing light on the unit ran the motor at 1000 RPM ,lower cylinder firing dead center of the two timing marks on the housing, top cyl. firing on the back mark(firing later than the lower cyl by a slight amount)how critical is this, will this effect top end, and if the timing is correct at 1000 RPM is it safe to assume that it will be correct at top RPM, is there such a thing as ballard stall speed for an outboard as in heavy marine applications, if so what is it

 

[Chinewalker]

Re: 1965 18HP Johnson outboard

Hi EZ,<br /> Not sure about Ballard Stall Speed, but your other stuff sounds like it's in the right ballpark. The timing on those motors isn't super critical and certainly not noticeable for most applications. If you were running your motor on a light hydroplane with an aggressive prop you might be concerned about that last 50 revs, but setting the points a .020 at 180 apart is good enough for most applications. You have to figure in wear at the point where the mag plate rotates on the motor, which if excessive can really throw the points outta whack. If things are fairly tight (mag plate doesn't wobble around too much) then you're good to go.<br /><br />I would run J6Cs, as I feel the J8Cs are probably too hot. The R-series plugs are resistor gap plugs and can play havoc with old style points/coils/condenser type magnetos.<br /><br />Those old 18s are great motors and with care will give you years of solid service. Make sure the lower unit holds oil and that the water pump impeller is relatively new. Have fun!<br /><br />- Scott

 

[EZ]

Re: 1965 18HP Johnson outboard

Thank you Scott. I have had this motor for years has been real good, but it has been slowing down and now it sounds like it is not topping out like it used to, have checked everything I can think of but nothing seems to solve the problem. As for lower end, I just rebuild it the pinion bushing was bad had to set it up in a Bridgeport and bore out the old bushing, which is cast into the lower unit made a new bushing out good quailty bushing brass and pressed it into the old bushing area, assembled with all new seals ,gaskets and recheck the unit before every outing, pinion bushing was a weak spot on these motors