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tapenick

stumbling at idle when in gear

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tapenick

85 Skier (PCM 351)

Been struggling with this issue - boat idles fine but when I put it in gear it starts stumbling and will usually die if I don't throttle it a little.

Tried replacing the entire ignition system (plugs, wires, cap, rotor, points to Pertronix), rebuilt the carb.

Thoughts?!

Tom

http://tapenick.googlepages.com

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JasonK

Maybe it needs the throttle/shift linkage adjusted by a professional. ? I don't know.

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99response

What are the idle RPM's set at, in neutral?

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tapenick
What are the idle RPM's set at, in neutral?

800

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footnlongline
Maybe it needs the throttle/shift linkage adjusted by a professional. ? I don't know.

That would be my guess, or If you have it in the water, maybe you got some wire around the prop shaft.

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electricjohn

Have you checked your timing?

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tapenick
Have you checked your timing?

Yes... timing is dead on.

Talked to skidim today and they suggested maybe the Anti-siphon valve in the tank or the fuel pump. Went to check that anti-siphon valve but it wasn't where I expected it to be. Have to look around on the net or call them back to find out... unless someone knows off the top of their head.

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multiplemalibufamily
85 Skier (PCM 351)

Been struggling with this issue - boat idles fine but when I put it in gear it starts stumbling and will usually die if I don't throttle it a little.

Tried replacing the entire ignition system (plugs, wires, cap, rotor, points to Pertronix), rebuilt the carb.

Thoughts?!

Tom

http://tapenick.googlepages.com

What carb did you wind up with on this boat? I had a very similar issue with an '86 skier I owned and through a bit of trial error found out my carb calibration was not was needed for this engine. In order to acheieve "idle" speed while in gear, the throttle blades on my carb had to be opened too much such that I was actually beginning to start the transition circuit of the carb flowing fuel at a lower rpm than was intended. As a result the engine would work itself into a mild surging which would steadlily increase in magnitude till the now radically fluctuating vac signal would draw harder on both the idle and transition circuits further enriching the fuel mixture at low rpm. Left to its own, the engine would eventually die and be hard to restart due to fowled plugs and excess fuel in the intake. A simple carb recalibration to set throttle blades at an angle to keep them from engaging fuel flow at transition circuit and a couple of small holes drilled in blades to bypass enough air for idle at low throttle blade angle corrected the problem. If this has been a nagging problem for you then a look at this is in order. Otherwise, idle mixture screws set a bit on the lean side while the boat is in neutral idling will often be too lean when the boat is put in gear. A simple check for mixure too lean is while at lake is to lift engine cover, start boat and let it idle till at operating temp. Place boat in gear and as it begins to surge, spray a very small quantity of something like WD-40 at the flame arrestor. If the additional Wd-40 cleans up the iodle surging then you have to look at a lean mixture at idle. If some reasonable adjustment to idle mixture screws does not clean up the problem and repeated WD-40 squirts to flame arrestor keeps you running, then it is highly likely you have a vacumm leak that wreaking havoc on your fuel mixture. Possibly not bad enough to affect idle quality in neutral, but it cause mixute to too lean while in gear as load is placed on engine.

Make sure you do the whole mixture check deal first before attempting a carb recalibrate like I described. Additionally perform your on water mixture enrichment with something like WD-40 in very small squirts and not anything like starting fluid or gasoline in a spray bottle. It is not necessary to remove flame arrestor for this test and it is not recommended that you do so. Looking down the throttle bores while the engine is running will do you little good for this problem.

This all assuming that all other tuning parameter such as timing, tempature, battery voltage and such are in order.

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tapenick
85 Skier (PCM 351)

Been struggling with this issue - boat idles fine but when I put it in gear it starts stumbling and will usually die if I don't throttle it a little.

Tried replacing the entire ignition system (plugs, wires, cap, rotor, points to Pertronix), rebuilt the carb.

Looks like it was the timing. I tweaked it and the problem cleared up. Not sure if I marked the balancer wrong or if maybe the outer ring slipped on the balancer. With the timing set so it was running well it was showing a few degrees off on the light.

Will never know, sold the Bu yesterday.

Thanks for all the help!

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