Please Help, 90 HP Johnson will not run correctly

[Firefighter615]

I have a 90 HP Johnson that I am having problems keeping it running. It is a 1984 Johnson 90 HP, MOD # J90MLCRD, Ser. # J6009772, it had a 13X19 Aluminum Prop on it and my mechanic said that it was to much prop for this setup so he loaned me a 17 pitch prop, on a 1983 Ranger 372V, the highest RPM (in gear) that I have been able to get out of it is 4800. Out of gear it will go much higher. This motor and boat did not come with a VRO tank and pump and I am not able to purchase one so I disconnected the VRO on the motor and plugged the line, I also disconnected the electrical coming from the pump at the motor.



When I squeeze the bulb most of the time it stays flat and I have to work with it to get it to expand again. I have an in line gas filter that I will be removing to see if this helps the situation.





I have to put the throttle about ¾ of the way down or about the 10:00 position to get it to start. Once it starts and runs for a few minutes I bring to throttle back to Neutral and the motor dies 95% of the time. If I do get it into gear at about 4000 RPM I have a miss every now and then, not all the time but you can here it miss about every 10 or 20 seconds.



This is what it looks like at the motor when I try to start the motor



I have two tanks in the boat that has 3/8ths barbs coming from the tanks to a manual fuel switch that also has 3/8 barbs on it as well, then it goes in to a fuel filter then the bulb up to the motor. I noticed on a friends boat that his 115 HP Johnson motor has 5/16 lines, is the lines that I am running to big for this motor?




Any and all help would be appreciated. I just want to take my 14 year old daughter fishing and NOT fight with the motor.

Thanks for all your help.

[ChampioNman]

In the top photo the yellow plastic fitting with the black rubber cover on it is what is used to cap off your oil lines. The black rubber cover goes over your oil nipple on the VRO pump and you secure it with a zip tie. The yellow plastic fitting would go in to your oil supply hose.
Make sure your filter is going in the proper direction, the filter itself isn't an issue. If you have an aftermarket primer bulb replace it with an OEM bulb from BRP. Get a 3/8" size (yellow fittings) an see if that helps. Running with a 3/8" fuel line is fine most V-4's use a 5/16" line so that shouldn't be an issue. Having to advance the timing that much is an issue. I would suspect a bad timer base. Make sure your butterflies are opening fully at wide open throttle. The motor doesn't need to be running for this, just remove the cover for the air box and move your throttle to wide open and make sure the butterflies are perpendicular to the carb bodies.
Your mechanic should be able to set the timing for you.

[Firefighter615]

Thanks for the help. I took the boat to the shop this morning and told him what it was doing and he told me that he thought that it sounded like the carbs needs to be rebuilt and the timing set. Thanks for all your help as always.

[ChampioNman]

Just trying to keep you on the H20.

[noelm]

just reading your post again, I think you have an issue that needs to be rectified long before the carbies are rebuilt, that being the fact that the primer bulb does not pump up/stays flat, that needs to be tended to first off, and do NOT rev the motor in neutral out of water.