90 Johnson GT150 - Slowly dies from WOT

[tobolamr]

Re: 90 Johnson GT150 - Slowly dies from WOT

Sorry, been busy...

Regarding motor mounts: I can't find them from that diagram; the pic breaks down too much when I blow it up to see it. Basically, there are bolts that hold the it all together where it pivots, and those are isolated with rubber bushings or whatnot, and those rubber parts are broken apart & gone. It appears that the motor had a chance, high-speed encounter with an immovable object in the past, and lost. I'm not going to spend that money until the dying issue is resolved.

Regarding dying from WOT: I have gone so far as to almost replace the fuel pump, when I was given the last bits of info I needed to check the carbs to see if they had some gunk in them that could be doing the deed. And last night, I had a tournament, and it started to die from WOT. I pushed in & held the choke, and it would lose power, then gain power, then lose, gain, lose, gain, etc, and got me the last 1/4 mile to our first hole. I'm now convinced it's carbs.

Thanks!

 

[tobolamr]

Re: 90 Johnson GT150 - Slowly dies from WOT

I called the dealer back on the outboard, especially after how it acted up this past Sunday. I thought it was going to jump off the transom! Ran somewhat okay all morning, then the last mile or so to the landing, seemed like it lost 3 cylinders. We could idle it at about 2000 rpm, but anything about 2250 & the motor would start to buck & miss horrendously. I'm going to let the dealer sort this one out now...

 

[tobolamr]

Re: 90 Johnson GT150 - Slowly dies from WOT

Dealer gave me the news that it would be about $2,000 for him to "start repairs" on the outboard. Debating if I should try to fix myself, and save some labor. My father used to turn a wrench, and we did all the maintenance ourselves on the dairy farm. I'm guessing that pulling the power head is a big job, but nothing that would be beyond a fairly mechanically minded person.

The last bit of the mystery is that I realized that the fuel system does not stay primed. I have to pump the bulb up vigorously, and re-build pressure prior to every firing of the motor. Is that normal? When I go to the lake for the first fire of the day, I have to squeeze it a lot, and can hear everything moving up into the carbs. On my bro-in-law's Nitro, with a v6 150hp w/6 carbs, he just has to give it a couple quick squeezes to firm it fully up and can go.

So, if I fix this thing.... My list would be as follows:
- Replace rubber motor mounts, top & bottom (Must pull powerhead to replace top mount)
- Rebuild all 3 carbs
- new plugs (again, 4th set since April)
- New plug wires
- New power pack (suspecting that after talking to another GT150 owner in my bass club, who has similar loss of power every 2-4 years)
- New fuel pump (What the heck - what's another $75!? ha ha)
- New lower seals around water pump
- new drain plug gaskets
- completely replace fuel line from tank to carbs - again - to be certain
- replace zip ties in system with hose clamps or actual plastic fuel line ties (I read elsewhere here that there is a difference that is important)

Or, should I just look into one of those $2-3,000 replacements on E-Bay that I could bolt on and run with? Or is it worth fixing this thing up? I don't know which would be wiser.

I would appreciate any and all constructive input, as I'm uncertain WHAT to do with this situation.

Thank you

 

[tobolamr]

Re: 90 Johnson GT150 - Slowly dies from WOT

JonesG:

Regarding the motor mount thing, I apologize for how long this has taken. I've been putting in huge weeks at work for the summer, and this morning finally made the time to get back regarding this...

TJ150SLESB 1990

I think they're talking about #18 on that diagram for the lower end... I'm not 100% certain....

But what I do know is that on Part #7, Steering Arm Assy... On the top at the back of the wishbone, there are the two points where everything bolts together. With the motor sitting just barely on the transom savor, if you grab the back of the cavitation plate, you can turn the motor about 1" - 1.5" WITHOUT making contact & turning the steering assy at the back of that wishbone. I was told that there are rubber isolation bushings that go there to help isolate vibration etc.

I do know that the motor flops around a little at low speeds - I'm always jockeying the wheel at low speeds and course correcting, because I turn the wheel slightly and it goes a lot. At high speeds, I only notice it when I make a major turn, which has been once all summer...

Again, input appreciated. Thank you!

 

[jonesg]

Re: 90 Johnson GT150 - Slowly dies from WOT

Rebuild carbs with new kits, run wire thru all the jets.

Test the ignition , get the factory manual.
Get a gap spark checker, do it by the book.
www.outboardbooks.com

Get a hoist, pull the powerhead and find out what needs replacing.

Or take it easy til cold weather hits, no WOT racing, its supposed to be fishing, not racing.

 

[tobolamr]

Re: 90 Johnson GT150 - Slowly dies from WOT

Or take it easy til cold weather hits, no WOT racing, its supposed to be fishing, not racing.

Hmmm... it'll take a while to get across 6,600 acres at 2,000 RPM



Got the power pack on order now. When I ordered the pack, the guy at the marina commented "Oh, yeah, maybe that's causing a lot of it for you!"

 

[Silvertip]

Re: 90 Johnson GT150 - Slowly dies from WOT

Actually, replacing the fuel line and bulb is not generally the fix for this condition. The problem is normally the pickup tube in the fuel tank or a tank vent problem. Every suck hard on an empty soda bottle and wonder why the sides cave in? What you suck out of the tank must be replaced by air. Or -- if the outlet of the tank is plugged the weakest spot in the fuel system will collapse. That weak link is the primer bulb.

 

[tobolamr]

Re: 90 Johnson GT150 - Slowly dies from WOT

I replaced the bulb earlier this summer, but I can definitely get another one and replace it again. What else would cause the fuel bulb to lose prime all the time?

Tank vent is OK - tested it and it vents without trouble. Pick-up is clean, checked that just before we lost the power pack. There's not a check valve in the fuel system before the fuel pump.

Maybe, if the power pack doesn't help things, I should take a video of what's going on and post it...

 

[tobolamr]

Re: 90 Johnson GT150 - Slowly dies from WOT

Okay! I think I got to the bottom of this thing!

Had the motor re-checked by the marina, and now they found 3 badly scored cylinders, amongst a host of other things. The Power Pack made a big difference, but the motor still runs badly. When the guys at the marina made a suggestion of the part needed to fix it, I took their advice.

So I fixed this 150 with a Mercury 200hp motor. SO! If anyone wants a GT150 for parts, let me know....

Even it parts, it was going to be a lot of money to fix it, especially now with the cylinders getting all scored to heck. Not a solution... But it was solved...