1967 Johnson 100HP chugging at full throttle

[jon705]

Well we've taken the boat out a couple times now after working on this outboard. She runs pretty smooth at idle and slow speeds but when I try to hit WOT she chugs. I've done the link and synch so at WOT butterflies on the carbs are wide open. I've cleaned the carb several times and I don't see any tears in the gaskets. Seems to me like she's starving for fuel. Any thoughts on what I should do next?

Also, can someone clarify that the adjustable needles affect idle speed only and that the high speed jets are fixed? In other words, if these needles are turned too far in or out will it cause my chugging at WOT symptom? I've had them as far out as 2 turns and as far in as 7/8 (per the manual) and she runs better at 7/8ths.

Thanks,

 

[F_R]

Re: 1967 Johnson 100HP chugging at full throttle

The needles are slow speed mixture adjustments, and have virtually no effect on high speed, which is fixed jets. Set them to where it idles the best and don't get hung up on how many turns.

Are you positive it is running on all four cylinders? Are you positive all four high speed jets are squeeky clean? Are you positive some cretin hasn't drilled them out to "give it more gas for higher speed"? (That doesn't work). Are you positive the belt timing is correct?

 

[jon705]

Re: 1967 Johnson 100HP chugging at full throttle

I have spark on all four cylinders, and each plug shows signs of firing upon inspection. I'll check the high speed jets again for signs of tampering and to clean yet again. As I tested the timing is correct. Would I have issues idling if timing were off?

This outboard also has the old style fuel pump with a glass ball that hangs down. I have a newer pump (model number 312668) that I was going to get a gasket kit for and put on in place of the old style. Any thoughts about the fuel pump being the issue?

 

[jon705]

Re: 1967 Johnson 100HP chugging at full throttle

Cleaned the carbs again yesterday. I soaked the high speed jets in seafoam for 8 hours then blew them out thoroughly with compressed air. Blew out all other passages in the carb with carb cleaner followed by compressed air.

Replaced the old style fuel pump with a newer one. Replaced gaskets on the pump, cleaned out all the passages with carb cleaner and compressed air.

All fuel lines are new.

She idles great. Starts up on first blip of the key, no hesitation, no choke needed. Don't even need to advance the throttle. Still having issues with WOT. Mid-throttle she runs fine but wide open she's still chugging.

Can someone help with the timing procedure? I've followed the manual but maybe I've not done something correctly.

Thanks,

 

[jon705]

Re: 1967 Johnson 100HP chugging at full throttle

After an offline conversation with Joe Reeves (thanks much) I found out that the original ignition system that was on my 67 was converted to an automotive type. I mentioned checking the point gap setting and Joe said it should be a solid state system with a sensor under the distr cap but no points. Also, the pulse pack had been completely cut off from the system although it still remains attached to the powerhead - the wires were just cut off and tucked out of the way.

Below is what led to the discovery. Keep in mind that many of "my" findings came with Joe's advice:

I set the timing by lining up the marks on the flywheel and powerhead, and on the distr gear and mounting plate. She still didn't run good. Then I decided to check the point gap setting. Upon first inspection of the distributor I found only one set of points when the manual called for two. I have a 66 parts motor so I thought to swap on a set of points from that motor. However digging further I noticed the rotor on my 67 was a "four bladed" type rather than a roller type with lobes. The point styles were also different on the two motors. I then decided to swap over the plate, rotor, points, and condesor from the 66 onto my 67.

After getting that all switched over she still didn't run right. I then swapped over the cap and spark plug wires from the 66 donor motor and she fired right up and responded well to my WOT request. I still have to get her out on the water for fine tuning but it seems my problem is fixed for now.

I'm not sure if just swapping over the cap and plugs would have worked on the single set of points and "four blade" rotor, but bad plugs/cap seemed to be the issue. Anyone seen only one set of points rather than two and confirm that it would work properly?

Thanks to everyone that has replied.