haunted 85 johnson javelin

[gonefishin485]

ok so ive come to the conclusion that im the proud owner of a haunted 1977 85hp johnson javelin.

i got this motor, mounted it on a ski boat project and got it running.
after many hours of testing, cleaning the carbs over and over again, taking every jet out, blowing thru the passages with an air compressor and running something thru the passages to make sure their clear, (sometimes at home, sometimes on the water) replacing the fuel lines from the fuel pump to the carbs, rebuilding the fuel pump, replacing the fuel line to the tank, replacing the primer bulb, and everything else i can imagine to get this motor right ive come to the conclusion its haunted, lemme tell you what the little ghosts and gremlins in it do.

i can crank it up and run it on the water hose for an hour or two and it will run and rev great. i can put it in the water and it will putt around at low rpms and rev in neutral just fine. when i full throttle the hot foot and get to cruising down the water, she shoots out like a missile and will scream at 5200 rpms with a 21 pitch omc prop for a couple thousand yards... then the ghosts and gremlins wake up.

it will start loosing rpms, and start to bog down. it wont stall but it wont go back to full throttle, sometimes if you let it run and idle for a while you can get it back running wide open, sometimes you have to pump the ever loving crap out of the primer bulb, sometimes if you hit the choke a couple times while your trying to plane out it will act right. either way the problem is always the same regardless of what i do. idle out the wake zone, get it up on a plane, go for a while and then the ghosts come out to play.

the motor has good compression on all 4 cylinders, hot spark on all 4, (pulled each wire off while it was running to try to find a dead cylinder, got shocked a bunch, wouldnt recommend it). drilled and tapped the water jacket for a tell tale and always have good water flow. so far the only way i was able to keep it going full throttle was while a friend i trust was driving the boat, i continually squeezed the primer bulb, pumping it, and it kept running at full throttle for quite a ways before my friend shut it down to wonder why it was running fine all of a sudden. so to try to eliminate as many problems as possible, i took the primer bulb off and hooked the fuel tank line straight to the fuel pump in the hopes i could find an issue with the primer bulb, line, or connections,but the gremlins re appeared.

i always feel like im so close to fixing this thing, but it acts up then im very close to turning this thing into an anchor. what is wrong with this thing?!? someone please help me before i lose my mind and the ghosts win. generally im good with outboard, i have a merc 500, and a suzuki dt 25 that run like clocks, but this haunted 85 is giving me the blues!

 

[theoldwizard1]

... so far the only way i was able to keep it going full throttle was while a friend i trust was driving the boat, i continually squeezed the primer bulb, pumping it, and it kept running at full throttle for quite a ways ...

You have an air leak some where in the fuel system.

On an engine that old, just replace all of the fuel line and the primer bulb. Make sure to use the appropriate clamps !

 

[itsaboattime]

ok so ive come to the conclusion that im the proud owner of a haunted 1977 85hp johnson javelin.

i got this motor, mounted it on a ski boat project and got it running.
after many hours of testing, cleaning the carbs over and over again, taking every jet out, blowing thru the passages with an air compressor and running something thru the passages to make sure their clear, (sometimes at home, sometimes on the water) replacing the fuel lines from the fuel pump to the carbs, rebuilding the fuel pump, replacing the fuel line to the tank, replacing the primer bulb, and everything else i can imagine to get this motor right ive come to the conclusion its haunted, lemme tell you what the little ghosts and gremlins in it do.

I'm going to throw out a guess and say you have issues with the pick-up tube in the tank. It runs well for a while then you have to pump the crap out of the primer bulb, is the bulb soft when you have to start doing that? Is it sucked in? Is it a built in tank or a portable one?
You have replaced the lines to the tank, but you never say if you worked on the lines in the tank. I would start there and work my way to the fuel pump.

 

[emdsapmgr]

Sounds like a weak fuel pump. The pump can't supply enough fuel to run at WOT. When at WOT, the carbs consume more fuel than the pump can supply. It will run low on fuel and go to idle. Once the pump refills the carb bowls, it will take off again. This cycle will repeat, until you choose some lower rpm to run at or replace eht pump. You can do a test. If you have a buddy constantly prime the fuel hose bulb when at WOT and it keeps running just fine, likely the pump is bad.

 

[gonefishin485]

Well its about 2 o clock, and I have the day off work so im off to try an experiment. Ive got my 6 gallon tank from my Suzuki dt25 and my fuel line from the same motor. Both of which work great as ive put many many hours on them crawfishing. So im going to go try that and see what happens. Report to follow this evening.

 

[canuckmark]

I have the exact same motor and had issues with tank venting. I'd also throw in checking the vacuum line from the fuel pump to the block.

 

[gonefishin485]

Well it occurs to me....im a dumb ass. I dont have a haunted motor, I have a haunted gas tank. I filled up my 6 gallon gas tank for my Suzuki dt25 which has an evinrude fitting on the tank since it was for an evinrude before I started using it for the Suzuki. Hooked up the fuel line that I had been using on the 85 johnson with the haunted tank, connected it to tank that is indeed not haunted, set out thru the wake zone as normal, got to the end of the wake zone and put the hot foot down and the boat took off and planed out as normal, in the back of my mind I was waiting for the ghost to reappear but as I passed the general area where the ghosts normally come out to play, I was turning 5200 rpms and not a sign of an unholy demon in sight. To test my theory I kept going, and going, and going, and well you get the idea. I burned almost 6 gallons of gasoline without the ghosts appearing. So my motor isnt haunted, fuel line doesnt have any gremlins, but my gas tank is indeed haunted. Anyone know how to exercise ghosts from a gas tank?

 

[ronward]

itsaboattime already gave you your answer. You probably have a crack in the pick-up tube or the tank fitting is leaking air in. At lower rpm's the motor uses a lot less gas so the leak doesn't show up. At high rpm's the demand is a lot more, your getting enough fuel to keep it running but your also sucking a lot more air.

 

[gonefishin485]

itsaboattime already gave you your answer. You probably have a crack in the pick-up tube or the tank fitting is leaking air in.

i pulled the pick up from the tank and cant blow thru it, and cant find any leaks or where it would suck air from. the pick up tube is solid with no splits or cracks and the fuel connector is solid and screwed in tightly. if you try to blow thru the pick up tube, as gasoline would flow thru it going to the motor, by mouth you cant blow thru it and i dont see a need to blow it with a compressor as there isnt that much suction going thru it.

i have however come to another conclusion since ive discovered another tank ran fine on it. the tank in the boat is one of the rectangle low profile tanks, 9 gallon i think. i havent filled it up since ive been doing the testing since i havent been riding very far. the way the tank had to be mounted, the pick up is closer to the side of the boat, and not the back of the boat. heres my hypothesis, since the boat is transom heavy and the pickup is mounted on the side, i think during take off and sometimes even when trying to cruise, the fuel is sloshing to the back of the tank and since the pick up tube has a crook on the end, its not allowing the fuel to be picked up.

however i was using the big tank when i did the bulb pumping experiment and the boat ran fine so at this point, im not sure