trolling probs with a 1960 lark

[surlyjoe]

I have a 1960 40hp with a model-C carb, problem is when it gets down to trolling speed (tach starts at 500r, so a bit below that) it will cough every once in a while, maybe every 2 minutes maybe sometimes. I think I have the mixture as good as you can get it since i've spent countless hours fooling with it , hardly ever kils it, but just kinda skips a couple beats, jerks and keeps rolling. are there any tricks to these carbs, to smooth em out? or should I be reading up on recharging my magnets?


I rebuilt it last fall, pretty much every replacable peice on the motor, including all the electrical and ignition


Thanks in advance!

 

[xmen3]

Re: trolling probs with a 1960 lark

Worn reeds is my bet.

 

[surlyjoe]

Re: trolling probs with a 1960 lark

hmm, didnt think of that.... how long do they last? i mean hour wise.. I think were maybe 200 hours.. if that

 

[tashasdaddy]

Re: trolling probs with a 1960 lark

have you used Joe Reeves instructions on setting carbs? it is in the engine faq forum. i have a '55 15hp rude that will troll all day and never miss a beat, after using this method.

 

[steelespike]

Re: trolling probs with a 1960 lark

Try adjusting the idle mix just a touch toward rich from smoothest idle mix setting.While the factory literature says they can troll I don't think they are real happy at that speed.I believe some run a step hotter plug when they do a lot of trolling.

 

[papasage]

Re: trolling probs with a 1960 lark

your air intake is under the carbs you might be gitting exzoust sucked up inside the cover . had that to be a probablem in a drum trying to set the carbs . the newer motors have a intake at the top

 

[surlyjoe]

Re: trolling probs with a 1960 lark

cover on or off, its the same.

I am gonna try some hotter plugs and I am gonna rich up a little from fastest idle like Joe says and try that. I'll let ya know tommorrow how it goes. Thanks again!

 

[F_R]

Re: trolling probs with a 1960 lark

It would be an excellent running 40 that would run less than 500rpm. Don't know for sure if I ever saw one that would. But then, maybe your tach is not accurate.

Coughing or sneezing is a symptom of too lean carb adjustment on the top (slow speed) needle. Just skipping a beat without sneezing is caused by igniton, likely points or plugs if the coils are good.

Magnets never need recharging on that motor.

 

[surlyjoe]

Re: trolling probs with a 1960 lark

sonds like the prescribed treatment will probably work then! d

 

[rwise]

Re: trolling probs with a 1960 lark

I run my plugs gapped a little wide, an extra 0.05 to 0.10 and it helps at trolling speeds. Mine is a '59 35hp

 

[Texasmark]

Re: trolling probs with a 1960 lark

When all else fails, decarb. Can't hurt anything.

Mark

 

[tashasdaddy]

Re: trolling probs with a 1960 lark

i agrre with Texasmark, if it has never been debarbed, Seafoam is in your near future.

 

[jimh6278]

Re: trolling probs with a 1960 lark

This is not a motor related answer but I solved a similar problem with a 150 force by dragging a couple drywall buckets behind a 20’ Trophy like a sea anchor. I was able to increase the RPM and keep the speed low. It really worked well and allowed me to quit using a kicker.

 

[surlyjoe]

Re: trolling probs with a 1960 lark

well, the hotter plugs and the mixture didn't help. and I decarb religiously..

However, while getting gas the other day, the regular pump wasn't working so I got the mid grade... lo and behold, it idles like a dream!! guess I'll be buying the 89 from now on...d

 

[byacey]

Re: trolling probs with a 1960 lark

Don't overlook the possibility of leaking cranckshaft seals. I just replaced mine and it made a big difference for slow speed operation.