1990 Johnson GT 150 will not plane!

[Caseyshoe27]

I have a 1990 Johnson GT 150. I have had it 5 years and has been running perfectly I always mix my oil directly 50:1 and never had a problem. Fast forward to about a month ago It cranks and idles perfectly on the hose or in a barrel. You can rev it up when you take it out of gear and its responsive. As soon as you put it in the water I can crank it and idle out and get ready for WOT and as soon as you hammer down it bogs down and dies. I can baby it and ease on the throttle and eventually get it to plane out and run WOT as long as I want but when I stop and try to plane again it bogs and dies.

I took it to a reputable mechanic and he replaced the stator, rebuilt carbs(had a few leaks), replaced all the gas lines and primer bulb. He said the power packs were good. I put a diaphragm kit in the VRO fuel pump ( Had a slight tear in a seal) that didn't fix it so that's when I decided to take it. I did notice the spark plugs were oil soaked so I replaced them as well.

I took it back this morning and he seemed kind of stumped.... And so am I. Im just running out of options Im beginning to worry its going to be something serious internal wise and cost me another arm and a leg I just spent around a grand like it is and its still not up to par.... He said he was going to do a compression test and pull the heads off and look inside. ANY IDEAS OR SUGGESTIONS? Thanks in advance!

 

[racerone]

Well, a compression test is the first thing to do in trouble shooting !----------Often it is the last thing done before the motor is declared to be a " dead horse "----But that is just my opinion.

 

[Chris1956]

Gee, do you pre-mix your fuel at 50::1 and still use the oil injection pump, or is the VRO pumping pre-mixed fuel only?

Since your motor will run at high speed, I would think your stator was good, and the mechanic didn't fix your carb issue. You probably have some sort of mid-range jet or orafice on your carbs. I would investigate those.

 

[emdsapmgr]

Agree with Chris. You may need to get into the carbs for some visual inspection. These carbs have 3 sets of jets, including a mid-range jet, also in the carb bowls. Possible one or more of these midrange jets has some dirt in it. That will kill the midrange. Once you can rev the engine past the mid, it will run wot on the high speed jets-like always. Not so sure that it won't run a little lean, however. I'd be wondering what was in the mid jet orfices....

 

[Caseyshoe27]

Gee, do you pre-mix your fuel at 50::1 and still use the oil injection pump, or is the VRO pumping pre-mixed fuel only?

Since your motor will run at high speed, I would think your stator was good, and the mechanic didn't fix your carb issue. You probably have some sort of mid-range jet or orafice on your carbs. I would investigate those.

The carbs have been taken apart by me and cleaned and taken apart and rebuilt by the mechanic. This was my first response when it first started acting up. Still had no effect sadly.

 

[Caseyshoe27]

Gee, do you pre-mix your fuel at 50::1 and still use the oil injection pump, or is the VRO pumping pre-mixed fuel only?

Since your motor will run at high speed, I would think your stator was good, and the mechanic didn't fix your carb issue. You probably have some sort of mid-range jet or orafice on your carbs. I would investigate those.

The oil injection has been capped and my vro is pumping pre mixed fuel only.

 

[David Young]

The first thing your should have done is what racerone said. Check the compression of each cylinder. You can rent a gauge from your local auto parts store for free. You pay a deposit but get it back when you return the gauge