56 fastwin 15hp only goes with the choke out

[Kelpy]

So it starts fine with the choke out and then idles up really high until i push it back in. Once its been warmed up a little bit it runs fine at low speed with the choke in. When I put it in gear and start to go I can twist the throttle up to about fast and it doesn't really go any more than about a heavy wake dragging speed and then it tries to die. When I get about half the throttle twisted (about the slow speed) and pull the choke out it goes just fine. I can then run on a plane (in a 14ft flat bottom boat) speed of about 16mph. If I push the choke back in it starts to cut out and dies. I have tried to mess with the needles and can't seem to get it to go any better (only worse).

Did maybe I mess something up when I did the carb rebuild? The motor goes just fine with the choke out so I am hesitant to mess with it as it seems to work without trouble. The only thing is that the boat goes 11 mph with my 7.5 fleetwin and only 16mph with my 15 fastwin. . . I'm guessing that running it with the choke out is costing some performance, or is that speed gain only to be whats expected?

Thoughts, ideas, things to check? Thanks, Kelpy

 

[HighTrim]

Re: 56 fastwin 15hp only goes with the choke out

It is running lean, there is something wrong. What is your low speed needle setting at? Did you replace the packing washers?

 

[boobie]

Re: 56 fastwin 15hp only goes with the choke out

I think you missed something in your carb repair. Are all the gaskets in the right place ?

 

[Kelpy]

Re: 56 fastwin 15hp only goes with the choke out

The motor idles really low (will go down to 2mph and stay running) before it starts to spit/miss on one cylinder. I replaced pretty much everything in this motor. Coils, points, condensers, etc. . . and rebuilt the carb so I know it is sparking well and running on both cylinders.

I don't know what the needles are at because I lost the screws to hold the knobs on with, Doh. I can't seem to find the screws in any parts lists either. They are close to the settings that are recommended here. I originally set them close to what my 7.5 fleetwin runs best on and it seems to do well. I have made minor adjustments and can't seem to get it any better.

That brings us back to the carb. I put it back together the same way that it came apart, only with new everything inside of it. Maybe it was put together wrong in the first place. This is how it ran when I got the motor (only with the choke out). There was left over packings and such when I was done and I was under the assumption that it was because there is several years that the carb kit covered and some weren't necessary. Is there anywhere that has a good instructional about taking the carb apart and putting it back together? I was really careful when I did it but evidently not as careful as I should have been. . .

Thanks, Kelpy

 

[AlTn]

Re: 56 fastwin 15hp only goes with the choke out

linknsync correct?

 

[SeaKaye12]

Re: 56 fastwin 15hp only goes with the choke out

I suppose you've already studied a parts diagram...but in case others would benefit, here's a link to one:

http://www.marineengine.com/parts/v...evinrude-johnson/ITEM_2747/ITEM_274700001.htm

 

[Kelpy]

Re: 56 fastwin 15hp only goes with the choke out

linknsync correct?

What is a linknsync? Are you referring to the linkage between the flyweel plate and the carb?

What is this and what should the settings be?

Thanks!

 

[AlTn]

Re: 56 fastwin 15hp only goes with the choke out

more or less I think we're talking about the same thing..the link SeaKay12 provided...magneto...the carb roller rest against the timing cam...there should be a raised or indented mark on the cam which is where your carb roller should be just as the throttle plate begins to open....when you advance the throttle to wot, the roller should be on the highest step of the cam and the throttle plate should be perfectly horizontal in the carb throat

 

[Kelpy]

Re: 56 fastwin 15hp only goes with the choke out

more or less I think we're talking about the same thing..the link SeaKay12 provided...magneto...the carb roller rest against the timing cam...there should be a raised or indented mark on the cam which is where your carb roller should be just as the throttle plate begins to open....when you advance the throttle to wot, the roller should be on the highest step of the cam and the throttle plate should be perfectly horizontal in the carb throat

Yes, the roller is riding on the flywheel plate just fine. It is off the edge of the raised ridge when the throttle is at stop and on the highest portion when the throttle is twisted all the way to fast.

Thanks

 

[HighTrim]

Re: 56 fastwin 15hp only goes with the choke out

There should be a couple packing washers behind each packing nut. Ensure the packing nut is tight and secure.

You can still tell your settings without the knobs by the cut slot in the end of the needles. Start them at 1.5 turns out from lightly seated for the low, and 3/4 out from lightly seated for the high. Did you replace all the fuel lines and fittings? If they are original the are NFG. What was the condition of the reeds when you had the carb off? What about the needles themselves?

 

[Kelpy]

Re: 56 fastwin 15hp only goes with the choke out

Ok, the needles looked good to me. No heavy grooves or anything. I took the carb completely apart as far as I could tell. Not sure what the reeds are. Everything inside the carb looked pretty clean. The fuel lines are old but I will replace those. Whatever the problem is it is consistent as it does exactly the same thing before and after my carb job. Maybe I need to go back through and try to re seat all the packings. I will get another carb kit and rebuild it again I guess.

I read somewhere that when the motor "coughs" back through the carb it is running lean. It does that at every once in a while at low speeds. Never at high speed.

 

[HighTrim]

Re: 56 fastwin 15hp only goes with the choke out

Yeah, as I stated in the first post, you motor is running lean. Lean as in the air/fuel mixture. Too much air.

You do not necessarily need a new carb kit, just need to troubleshoot some more. I would start by replacing the fuel lines and ensuring the connections are tight. Also ensure the packing is adequate and the nuts tight. Start with the low speed needle 1.5 turns out from lightly seated. If this does not solve the problem let us know and we can troubleshoot further.

 

[nwcove]

Re: 56 fastwin 15hp only goes with the choke out

dont see any mention of the welch plug being pulled or any mention of the passages being cleaned with a wire? just a thought.