'58 Johnson 18HP points adjust effect

[asdasc]

Background: My 18hp had new coils when I got it, so I never pulled the flywheel. It starts right up, idles nice, lacks power - but I attributed that to a very heavy pontoon boat. It was very smooth and quiet.

A buddy has the same motor and I saw it running for the first time the other day, huge difference, so I knew something was wrong. Upon further investigation, I had a bad plug and was running on one cylinder. Thru the inspection plate I can see the points are not adjusted right. They are close to .040 (double what they should be). It no longer runs very smoothly, but has LOTS more power.

Question: I know the points gap effects timing, how urgently do I need to pull the flywheel and fix that? Am I doing any damage? My guess is that since I wasn't able to get any RPMs in the past, timing wasn't an issue. Now that I can turn more RPMs, it probably is a bigger issue.

PS I can't adjust them thru the inspection plate, they ran the points ground wires across the adjusting screw.

 

[56 rude]

Re: '58 Johnson 18HP points adjust effect

yes adjust points .040 is way too much!thats twice whats called for!

 

[asdasc]

Re: '58 Johnson 18HP points adjust effect

Thanks, I know I will need to eventually. The question is am I doing any damage until then. I am up at the cottage and don't have my flywheel puller. Should I still run the boat?

Thanks!

 

[tx1961whaler]

Re: '58 Johnson 18HP points adjust effect

You won't do any damage, but it may quit running if it's running rich (weak spark) and you foul the plugs.....

 

[asdasc]

Re: '58 Johnson 18HP points adjust effect

OK, thanks. I can keep extra plugs with me and a wrench.

 

[crxess]

Re: '58 Johnson 18HP points adjust effect

Keep extra plugs on board. Keep RPM down a bit

Effect of point gap.
Wide gap - points open (fire) to soon - Recharge time to short - Weakened spark at WOT

Narrow Gap - Points open late - Long recharge - Poor spark - flame chases piston - low power

 

[asdasc]

Re: '58 Johnson 18HP points adjust effect

Excellent information, thank you!

I suppose this means there is no point in trying to adjust the carb yet then. I made some rough re-adjustments to make it run a little smoother, but I will reset the point before really dialing it in.

Thanks for the help,

 

[jbjennings]

Re: '58 Johnson 18HP points adjust effect

I don't believe you need to pull the flywheel to set the points. You should be able to do it through the flywheel window. I'm suprised you're getting spark with the points that wide. You'll really be pleased when you get it tuned right.
Later,
JBJ

 

[asdasc]

Re: '58 Johnson 18HP points adjust effect

I was out at the cottage yesterday, and somehow forgot the gear puller sitting at home on the table by the door. I may try running out there again today if the rain stops.

The little wires that get screwed to the coils run right across the set screw on the points and I can't get the set screw loosened thru the inspection hole with them in the way. I will try it again before pulling the flywheel.

 

[asdasc]

Re: '58 Johnson 18HP points adjust effect

An update!

Sunday I was back out there and remembered the gear puller. I reset the points and am firing on all cylinders now. Big difference. I figured I would have to re-tune the carb and went to do the high speed run first. I adjusted it in, no diff. I adjusted in again, no diff. I kept doing that until I had it screwed in all the way closed. Still no difference. It had only been out about a half or 5/8 of a turn from when I had mistakenly adjusted it on only 1 cylinder. Thinking back, this may have been my mistake. I didn't start it back out at 1 and a half to 2 turns initial setting.

Would it still run with the high speed needle closed? Or do I have another problem to fix first?

Thanks,

 

[tmcalavy]

Re: '58 Johnson 18HP points adjust effect

Initial settings: high speed, 3/4 turn out from gently seated
low speed, 1.5 turns out from gently seated
Get it started, put it in gear and throttle up...then adjust the high speed to find the sweet spot. Throttle down to idle, adjust the low speed to get the best idle. Tighten the retainers around both jets. Bob's your uncle!

 

[asdasc]

Re: '58 Johnson 18HP points adjust effect

Thanks tmcalavy, that is what I was trying to do. Although, I started at closer to a half turn on the high speed.

Isn't it odd that it still seems to keep running fine at WOT with the high speed all the way in (closed)? I ran for more than 30 seconds that way, with no end in sight, so I figured something else was wrong with the carb and I opened up to where it was, throttled back to mid and cruised in.

 

[coolguy147]

Re: '58 Johnson 18HP points adjust effect

ya thats quite strange about 1/2 turn it should start to die out when u turn in. i wouldnt think dirty carb but maybe some abd gasket or something