JOHNSON V4 90/65jet

jetsled74

Cadet
Joined
Jul 6, 2011
Messages
9
Looking for some advice. Here's the scenario. When full throttle boat goes on plane runs fine for about 40seconds then just drops off plane doesn't stall out just seems like i have a cylinder or 2 dropping out. I checked fuel prime i am not losing fuel bulb is hard and by choking when this problem occurs it stays the same. I go back to neutral open throttle back and its on plane full speed 40 secs and same thing keeps occurring. A while back i had a big loss of power all around was not cutting out like i have now. I had a new powerpack installed new plugs and wires coils were checked and said to be fine. Since then i am experiencing the cutting out. Can this be thermostat issue carb issue? I would like to rule out as much i can on my own before taking for service. I feel confident its not a fuel pick up issue because i am not losing prime and when it boggs down supplying more fuel does not solve the problem. Any advice would be great.
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: JOHNSON V4 90/65jet

When the prob occurs pull one spark plug wire at a time and see if you can nail it down to any cyl/cyl's. Could be a spark or fuel prob. Or else squirt some premix fuel in the carb throats and see if it picks up or not.
 

AlTn

Commander
Joined
Mar 9, 2010
Messages
2,813
Re: JOHNSON V4 90/65jet

fuel tank venting properly?...the bulb should become "soft" as it essentially becomes part of the fuel line as the engine runs. Got access to another tank and fuel line to try? Have you tried running with the fuel cap loose to rule out a venting <vaccumn> issue in the fuel delivery ?
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Re: JOHNSON V4 90/65jet

When it cuts out does it ack like a light switch was flipped, or is it a little smoother and just bogs down? Electrical problems typically act like a switch is turned on or off, fuel problems normally act a little slower and smoother.
 

jetsled74

Cadet
Joined
Jul 6, 2011
Messages
9
Re: JOHNSON V4 90/65jet

When it cuts out does it ack like a light switch was flipped, or is it a little smoother and just bogs down? Electric problems typically act like a switch is turned on or off, fuel problems normally act a little slower and smoother.

It is more like a switch is thrown sudden loss of power. I have tried with open fuel cap. I have changed fuel. The ironic thing is it never stalls out and after i go to neutral after the bog down and go full throttle it takes off only to repeat the process. Originally it started with just loss of power took to shop they changed plugs fuel pump screen and fuel filter checked coils set timing replaced powerpack and now i have this problem. Unfortunately i wont be able to get it out on the water anytime soon due to ice. Appears the waterflow out of tail not flowing like it should be either. Sorry to be so vague i was just looking for a few things to do myself in hopes of not having a big bill this spring
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Re: JOHNSON V4 90/65jet

Next possible issue.

Look at the reverse gate on the pump. If the cable get's out of adjustment the gate can move and partially cover the nozzle, this causes a sudden loss in power that can feel like an engine problem. It's easily fixed by adjusting the cable.
 
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