Loss of power

jetsled74

Cadet
Joined
Jul 6, 2011
Messages
9
Running my 1993 Johnson v4 90/65jet have loss of power issues. Starts fine idles sweet my problem occurs at full throttle boats goes up on plane runs for a time(usually the same amount like 30 seconds) then a sudden bog like i lose 80% of power and come off plane. Almost like all a sudden no fuel, however bulb stays fine it doesnt appear to be starved for fuel. I also made sure tank is vented. This occured awhile ago where it appeared engine was running at only half power all the time. Power pack and plugs were replaced and was told coils are fine. Where would be a good starting to point look? Its almost like it gets hot reaches a temp and shuts down can something be sticking?
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: Loss of power

When the prob occurs, pull one plug wire at a time and see which cyl/s are not firing. Could be fuel or ignition.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: Loss of power

Possible weak fuel pump. The engine may be consuming more fuel than the pump can deliver. When the engine slows, try priming the fuel hose bulb constantly. This will force extra fuel around the fuel pump into the carbs. If the engine runs fine while you constantly prime the hose bulb, likely a weak fuel pump.
 

jetsled74

Cadet
Joined
Jul 6, 2011
Messages
9
Re: Loss of power

When the prob occurs, pull one plug wire at a time and see which cyl/s are not firing. Could be fuel or ignition.

Thank you i never considered that. I thaught if it was coil related i would see the problem at all speeds. What i failed to mention was that when this happens i put it back in neutral start up slowly increasing speed to wide open and then bog down again. This just keeps reocuring.
 

jetsled74

Cadet
Joined
Jul 6, 2011
Messages
9
Re: Loss of power

Thanks for your response. I have tried that before and it would not change. I tried a different fuel tank and hose and primer bulb as well. What i failed to mention is that when this happens ill go back to neutral restart gradually increase speed when wide open again same amount of time roughly 30 secs and wham bugs down again.. Hoping to get on water soon i will recheck the fuel bulb and test as you advised.
 
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