1987 Gt 150 carborator adj.

I been fighting trying to get good rpm at wot with my engine. I been to prop section tried going from 22 pitch down to 19 and still only pulling 5200 at wot on a 17 foot runabout. I just checked tonight the carburetors and when I engaged the throttle all the way I went back and I still could move the linkage on the carbs a good ways. When it is at full throttle should the butterfly's be wide open and if so do I gain that by adjusting the flat adjuster there????????????

Re: 1987 Gt 150 carborator adj.

The butterfly valves should be perfectly parallel and horizontal (but not beyond) at WOT. you'd want to take the airbox cover off for visual inspection before making any adjustments.

are you trimming up after it gets on plane?

Re: 1987 Gt 150 carborator adj.

yes as far as it will go without venting

Re: 1987 Gt 150 carborator adj.

Ok jTexas, I just checked and they are not perfectly straight. they are tillted down a little looking from inside the boat. and thats the back up and the front down.

Re: 1987 Gt 150 carborator adj.

they go too far.

I can't picture what your's looks like exactly, but on the starboard side of the engine there's a WOT throttle adjustment stop screw that limits the travel of the throttle lever. It's a set screw near the bottom. Should be spring loaded, to keep it from vibrating in & out.

Any other symptoms? accelerates, idles, starts ok?

Re: 1987 Gt 150 carborator adj.

Have you done a link 'n' synch by the manual?

Messing with carbs and/or stator without the manual is sure to lead to grief.

Re: 1987 Gt 150 carborator adj.

It idles good at 700 rpm, a little shaky in gear. I just had this engine put on a few weeks ago and I was looking at the cable adjustments tonight and the throttle one you can see were it was when the other owner had it. I have noticed though that when I put it in gear one click it puts it in gear and idles i assume a no wake deal. I go past that first click then it should start throttling but there is a brief laps maybe about a half inch of throttle forward before I get any response. Could that be a stretched cable and therefor causing my cam not to push the butterfly's open all the way to perfectly horizontal????????? And If so I adjusted them to were they were horizontal but I marked were it was just in-case I should put it back and have another mechanic look at it. I haven't run it.

Re: 1987 Gt 150 carborator adj.

maybe I'm confused - if they tilt down (aft side higher), doesn't that mean they've gone past horizontal?

No matter, they're horizontal now, give her a test run.

Doesn't sound like you're describing more than a normal amount of throttle travel after shifting. There is an adjustment to fine tune the cable length where it enters the engine, but changing that affects other adjustments (idle stop, wot stop, cam roller, what'd I forget?)

The throttle lever also coordinates the spark advance with throttle valve opening - the syncronization procedure isn't difficult but it varies from one model to the next. A manual is pretty much a necessity to get it dialed in just right.

Have you done a compression test?

Re: 1987 Gt 150 carborator adj.

Yeah I didnt want to mess with all that other adjustments without a manual. The Mechanic who installed it is supposed to be pretty sharp so I'm going to take it for a little test run now. The compression is right at 90 pounds on all cyl. I think one cyl was around 87 or so. other than that they were all the same. I'll let ya know the results of the test run in about a hour. Thanks for all the help here. Chris

Re: 1987 Gt 150 carborator adj.

After adjusting cam I took it out and it did gain me a couple hundred RPM. There just happen to be a mechanic running new boats at the dock yesterday and he said everything was ok with my engine. He suggested a 18 pitch prop for the size of my boat. Well see. I'm calling around now to see if anyone will trade my 22 pitch raker for a 17 pitch.