86 GT150 losing power above 4000 rpms...(posted on Ranger board also)

Let me first say that my 1986 GT 150 starts and runs like a top most of the time. Ocassionally it will studder just for a second at rpms higher than 4000. When you ease back on the throttle the problem goes away. I believe this may be a fuel restriction problem as the boat sat for many years unused. What leads me to this conclusion is the primer bulb is not always firm. I have replaced the bulb with no change. The other work that has been done on this engine all carbs have been rebuilt with new gaskets to handle the alcohol in todays gas. The VRO pump and fuel pumps were replaced / upgraded. I have checked the ball check valves and the anti siphon balls were already removed so no debris would be clogging the valve. The water seperator has a new filter in it.
Kind of at a loss as to what else to look for. I was hoping some of the "older Ranger" owners would have some ideas....

Thanks,
Brian

Hello Brian,

Your 1986 GT sounds a lot like my 1985 XP 150 when I put in in back in service after a years of storage.
Well, I had to replace most my electronics. Hopeful, you will not have to. My suggestion is to start with the basics.
1. Check the compression
2. Do a leak down test.
3. Clean the carburetors.
3. Check the recirc valves.

OBTW, did I forget to say get a good Johnson/Evinrude manual before you start.

Record information. . . and report back to the moderators they were a tremendous help to me getting my engine back in shape.

My son's 150 did the same thing, after plugs, new gas, motor gas lines,gas filter, rebuilt fuel pump, then it got to where it would run barely above a idle, so we idled back to the launch, (1 mile+) while I squeezed the primer bulb. I removed the pick-up tube from the gas tank & there was a huge clump of silicone in the pick up tube. removed, then ran perfect. Before you try anything else, borrow a 6 gallon tank from someone, connect to motor, & see if it clears up. You will have to temporarily modify the fuel line to work. It will be easy. Or just completely check fuel line from end of pick-up tube all way to motor if you can remove the pick up tube. Some boats you can't even see the tank, more less remove the pick up tube.