1966 Johnson 33hp running issues

[acdc96]

Hello all,
I recently took my 66 Lonestar del ray out for some sea trials. The Johnson fired right up and motored around the harbor just fine. But as soon as i tried to get up on plane it wouldn't go full throttle and would skip at certain points consistently, so I adjust the high speed idle lever/screw to make it more rich and nothing changed.
Last year I rebuilt the carb and put new fuel lines on. I've replaced: spark plugs, lower unit seals/gaskets, impeller, propeller, throttle and shifter cables.
Any ideas what it could be?

Fuel pump, cut off switch, etc.?

 

[lindy46]

Check compression, and then spark. Should jump a 5/16" gap on a $10 spark tester with a snappy blue-white spark.

 

[jimmbo]

Did it run fine prior to the carb rebuild? Also, when you put the carb back on did you do a link-n-sync?

 

[acdc96]

I bought the motor last year and never had it on the boat until yesterday. It ran great on the test stand and starts right up every time but every time I try to go past 1/2 throttle it woundnt come up on rpms.
I don't know what a link n sync is?
But I know the throttle plate opens up all the way at full throttle.
I will do a compression test now and spark test and post results when done. But it has plenty compression by me just trying to turn it over with the pull start.

 

[jimmbo]

I bought the motor last year and never had it on the boat until yesterday. It ran great on the test stand and starts right up every time but every time I try to go past 1/2 throttle it woundnt come up on rpms.
I don't know what a link n sync is?
But I know the throttle plate opens up all the way at full throttle.
I will do a compression test now and spark test and post results when done. But it has plenty compression by me just trying to turn it over with the pull start.

Running on a test stand means no load, no exhaust backpressure. engines always run great, even when half the cylinders aren't firing.
Link-n-sync is the coordination between spark advance and carb opening
Ok the carb is opening, a misadjusted linkage can do that without properly advancing the spark

 

[oldboat1]

If adjusting the high speed needle has no effect, it sounds like the h.s. jet is blocked. Might pull apart the carb again, disassemble and soak then finish with carb spray. Guys have other techniques, but the point is to get both the high speed and low speed sides squeaky clean. It may also be that the skip you describe is a stumble (too rich). It's counter intuitive, but leaning out the mix may give higher rpms (either idle mix or h.s. mix). When you get the adjustment dialed in, you want to make sure the gland nut is snug, or the needle will vibrate loose and change motor operation while under way.

 

[F_R]

Good thinking in most cases. However, doesn't that motor have an adjustable High Speed jet? The hole through that thing is huge. It would be pretty difficult to plug it up. My money is on it is running on one cylinder.

 

[oldboat1]

Yup -- could be. Let's see, two person job to check for cylinder drop -- helper to run it at WOT, letting you do a drop test at the motor. When it acts up, pull one of the plug wires and see if there is a change (no change means that plug isn't contributing...) Leather work gloves are recommended. A more elegant way is to use a timing gun -- clamp on to the individual plug wires to see which one isn't firing.

 

[F_R]

O.P. said on original run it wouldn't come up to speed, so he opened the H.S. needle. That might have been the exact wrong thing to do. Maybe it is too rich. Anything over 3/4 turn is impossibly rich to run. It'll just blubber along.

 

[todd281]

I have the same motor. Just a note, when I rebuilt the carb on mine last year, it ran fine for the season . This year I had problems. After some research, I found that the pin that holds the float hinges on is made of some kind of plastic. It had swelled some [ I assume from submersion in gas] and would let the float move , but not freely. So it would flood at times, and starve for gas at other times. I replaced it with a metal one, and it has been running great ever since. good luck with it