1992 GT150 sluggish under a load...Need ideas please...

[pikeslammer]

Hello. I have a 1992 GT150 powering my 18ft Nitro. Mod#TJ150SLCEM, S/N#R08187828.Took her on her maiden voyage yesterday and had some issues. She starts right up when choked and the throttle is advanced. Once warm, I tried to bring it back to neutral then advance it forward into gear. At first it would die. When I was fast enough to make the transition from the warm up position to forward the boat was sluggish. Could not even get it onto plane. I spent awhile toying with it . I checked the fuel tank selector switch and moved it to main, then opened the fuel vent on the side of the boat. I pumped the primer bulb until firm, but when it would run it would not stay that way. Out of the blue she began to run very well. I could advance it almost wide open (too rough out, and too new to go WOT) did 36mph on GPS. I could idle it run it reverse, forward without issue. Ran great from then on for two hours.
I ran it about 2 miles to a fishing hole of mine (not one issue). My fishing partner and I fished for about 3 hours. (the motor not started in that time frame). We then began the return trip. It was a chore. I could not keep her running unless I kept pushing the choke switch in. Then it was only at an idle. It was a long trip in but we made it.
It seems to be starving for fuel under a load. When it is in warm up position, I can hit the rev limiter. I checked for fuel leaks and found none. I did replace the primer cap and valve kit, as well as the black housing it fits into. That ended my fuel leak when I choked it.
Please give me ideas as to what it could be. Fuel system, spark, compression. Need a direction to begin with.
Thanks, Alex

[ChampioNman]

Red valve pointing straight down? Throttle plates opening fully? Clear plastic roller on center carb touching small embossed mark on cam follower? QL77JC4's gapped at .030 in the cylinders? Head temps? OMC/BRP primer bulb 3/8" ID?

[pikeslammer]

In reponse to your questions:

Red valve pointing straight down?NO Throttle plates opening fully? YES, SEEMS TO.Clear plastic roller on center carb touching small embossed mark on cam follower? THE MARK IS LINED UP BUT THE ROLLER WHICH IS WHITE PLASTIC IS BROKE OFF.THE ONLY THING LEFT IS THE METAL PIN THE WHITE ROLLER URNS ON. QL77JC4's gapped at .030 in the cylinders?DON'T HAVE NEW PLUGS YET, I HAVE THE NGK EQUIVLENT WAITING FOR PICK UP, THE EXISTING PLUGS WERE FLOODED AND I AM NOT SURE OF THE GAP. Head temps? HAVE NO IDEA, BUT WOULD BE INTERESTED IN FINDING OUT. WHAT TYPE OF THERMOSCANNER DO YOU RECOMMEND? OMC/BRP primer bulb 3/8" ID? YES, HAS THE STOCK STYLE PRIMER BULB.

I HAVE INCLUDED PICTURES I TOOK OF THE CHOKE ASSEMBLY. WOULD ANY OF THE ABOVE POSSIBLE PROBLEMS ALLLOW THE MOTOR TO RUN POORLY, THEN PERFECTLY, AND FINALLY POORLY AGAIN? I APPRECIATE YOUR TIME.

[Bassmeister]

The red lever is pointing along the body is correct. You do need that roller,as the timing needs to advance first or at the same time. That alone should help some.

[JoePA]

If you have a can of de carb you can cut a piece of that tube and use it as a roller for the timing...think I picked that one up from ChamioNman or Rusty. I had to use a piece from a can of fix-a-flat.

[ChampioNman]

Yep as the Jr mod says the lever is pointing correctly. Get rid of them NGK's there for Mercs and Hammers. Once you get the replacement roller you'll need to go back and do a proper sync n link. You can get a IR thermometer at a Harbor Freight or Northern tool or you can use themo sticks. A good de-carb with BRP engine tuner will help too. Check your recirc valves also they are 3 on each side of the intake manifold. One per cylinder. Follow the small hoses from the block to the intake. It is a one way check valve. Brass with a membrane and screen on the motor side and a nipple to the hose. 3/8" socket will get them out.

[pikeslammer]

Yep as the Jr mod says the lever is pointing correctly. Get rid of them NGK's there for Mercs and Hammers. WHAT ARE MERCS AND HAMMERS? Once you get the replacement roller you'll need to go back and do a proper sync n link. FOUND A PERFECT MATCH WITH A PIECE OF LATEX TUBING FORM WORK.WILL HAVE TO DO THE SYNC AND LINC WHEN IT QUITS SNOWING OUT.You can get a IR thermometer at a Harbor Freight or Northern tool or you can use themo sticks.OK I GET THE THERMOMETER AND GET THE TEMPS, THEN WHAT? A good de-carb with BRP engine tuner will help too. I PUT A CAN OF SEAFOAM IN THE TANK WHEN I FILLED IT WITH FUEL. WILL USE THE PONY TANK METHOD ALSO WHEN THE SNOW STOPS.Check your recirc valves also they are 3 on each side of the intake manifold. One per cylinder. Follow the small hoses from the block to the intake. It is a one way check valve. Brass with a membrane and screen on the motor side and a nipple to the hose. 3/8" socket will get them out. SEEM TO BE MISSING THIS ONE. LOOKED FOR THEM ON THE MOTOR WITH NO LUCK. I AM CURRENTLY LOOKING FOR THEM IN MY SERVICE MANUAL. I APPRCIATE YOUR TIME.
THANKS,ALEX

[ChampioNman]

NGK= Mercury or Yamaha plugs the OMC's run best on Champion plugs. Yours Champ Ql77JC4.
For the recirc valves they are in the center of the intakes you have to LOOK! Loose the SEALOC manual or Clymers If you want to maintain the motor get of the hip and get the Shop manual. Don't want to sound harsh but..you get what you pay for. The X-flows aren't that hard of a motor to understand. Read the book and you can figure it out you said you can fix ski-doo's

[pikeslammer]

Thanks for your input as always. I don't consider you harsh and I agree with you, you get what you pay for... which is why I have the Johnson Cross V Service Manual. I will take your advice on the plugs.

I am sure they are not difficult to understand, but understand my position. I spent more on this boat than I have on any car or truck I ever bought. As such I ask alot of questions and check twice before diving in over my head. This motor is also newer and bigger than anything I have ever worked on marine-wise. My experience has been with mostly 50hp or less omc, no newer than early 70's. I have a strong mechanical abilty, ask questions and take direction. If it was in my budget to have an omc mechanic run through it I would. It's not so there is only me.

I plan on looking for the recirc plugs again tomorrow. Thanks again.

[ChampioNman]

On the port side you'll have to take of the starter and VRO pump.

[pikeslammer]

All fixed. Gave her the best tune up possible. Didn't help. Changed fuel filter and lines, no help. Tightened all the loose bolts in the heads and waterjacket, that stoped the new leak I noticed but no help. Put dry gas and lots of sea foam in the tank, no help. Finally hooked up a pony tank with fresh fuel and she ran great. The best feeling I had in awhile. So I am draining my fuel and changing all the hoses from the tank to the motor.
Thanks for all the input.
On the water by the weekend if the dang snow will go away1

[Mr Limpet]

Sometimes the advance mechanism under the flywheel (starboard side) will get disconnected - result, no timing advance and a sluggish motor. You gurus know the technical terminology.

[pikeslammer]

And the saga continues....Changed all the lines and primer bulb. Checked the pick up tube and re-sealed. Took it out ran fantastic..Lined up a fishing buddy last Saturday and unloaded the boat. Fired it up and blah! Same, exact issue as before. No power when under a load. Fished using the trolling motor. The OMC marina returned my call and we tried to get back to the launch to take it in. The only way I could keep it from dying was to throttle wide open and push and release the choke. Halfway back I shifted it out of gear to burn off some of the fuel I had been flooding it with, then shifted it back into forward. She came alive WOT in a no wake zone. I took it into the bay and ran the hell out of it and it ran great again. I knew there was still an intermittant issue, same as before and so we took it back, loaded up and drove to the johnson dealer/marina for further evaluation. Spoke with the mechanic, and described everything I have done to this motor. His initial diagnosis was a possible weak and failing VRO. Told me to check back on Monday.
Called Monday to get a status report. Now there are two mechanics (the head guy and the one I spoke with) working on it. They are not so sure it is the VRO now but were still trying to get the motor to repeat the failures I have had. So far she has ran great every time they tried it. Rather than just pulling parts and replacing them, they are trying to have it fail, and then start with that.(which is greatly appreciated by me) I told them to keep it till it does so and if it doesn't fail by the end of the week, I'll plan a fishing trip, grab my buddy and head over to take it out. It will fail for sure then.

So that is the current state of affairs. The marina just opened for the season, and now I have a pro doing what needs done to fix the damn headache I have been having. I will post the results of their evaluation and the repairs done to fix the problem, in hopes of helping others deal with similar issues. Thanks again for all the input. I went as far as my limitations would allow and now it is time for the more knowledgable to take over.

On a side note I was able to get it to 49 mph GPS on 21p stock prop. Does anyone have an idea of what this rig could be capable of speedwise with say a high perfomance prop 22-24p ??

Stay tuned......

[ChampioNman]

The Nitro guys can answer that better.

[pikeslammer]

Took the mechs at the Johnson dealer to get her to fail but she finally did. I applaud those guys, they could have just began pulling parts and telling me that what they replaced was the issue, but instead they kept pushing it until it acted up. Turns out the coil pack would fail and I would lose spark to one whole side of the motor. Then it would be fine. I had asked them to check the Tach as well because I noticed it acting up, and i guess that was a big clue to my issue as well. Anyway, I pick it up next week and will give an exact breakdown on what was replaced in hopes to help someone else.

Thanks again for all your input.