15hp 2-stroke woes

[rednwhite]

I picked up a 14' v-hull boat with a 15 hp merc last fall.

Motor is model 1015201LD, serial 0D002971. The carb is this one: https://www.crowleymarine.com/mercury-outboard/parts/496_110.cfm?mdl=YC3Z8P

This engine sat for several years with fuel in it and was not running well, so I rebuilt the carb.

I picked up the appropriate gasket kit (sierra). It came with a paper gasket that was not present in the original carb --between the diaphragm (20 in the diagram above) and the pump body. I installed it, but I'm not sure it's necessary. After getting everything back together, it ran great for about 20 minutes. After the initial run, it died, and became difficult to start. Once started, it will die shortly unless I depress the diaphragm pump button that's affixed to the side of the bowl. After pressing the button, it runs for a minute or two and begins to die again until I depress the button again.

I have rebuilt several two-cycle carbs, but am new to outboards. Does anybody have advice on how to troubleshoot this? I'm planning to check the float level and re-clean the jets.


Thanks

 

[hardwater fisherman]

The "button" on the right side of the carb is a primer... And used for starting and or warm up...Did you rebuild/inspect the fuel pump? Or just the carb itself?

 

[rednwhite]

Thanks. Found that after a bit more searching. I rebuilt the pump and the carb. Prior to rebuild, the primer was stuck in the down position.

 

[flyingscott]

Did you replace the waterpump? what is the compression? The carb kit covers several different carbs. Did you soak the carb or just replace parts? Did you look at/replace the ball and spring on the primer?

 

[rednwhite]

Thanks for the help.

I replaced the impeller -- full water pump kit is on the way. Compression is around 100 in both cylinders. Didn't soak the carb, but I did spray thoroughly with carb cleaner. Pretty sure all of the jets are clear. I didn't replace the ball & spring from the primer (almost lost the ball - glad I cleaned it in a pan), but I did remove them and clean everything with carb cleaner.

Based on hardwater fisherman's comments, I took a closer look at the choke assembly and found that it was not engaging. Reinstalled and it's working as it should now.

I also took a look in the fuel line from the tank, and it looks like it has a plastic lining that is collapsing -- maybe that's what restricted fuel flow. I'm going to replace the tank and hoses and will post here if it's still giving me problems.

 

[QBhoy]

Hi. If new to it all, welcome, but you may or may not know about the vent on the tank needing to be clear and open. Just throwing it in there...haha. All the best.

 

[rednwhite]

Thanks. I appreciate all of the help. I did read about the tank vent.

I just switched to new hoses and tank, and still see the issue, though it is smoking a lot at idle (which seems to point at the primer ball). This really seems like a fuel supply issue. I double-checked the service manual and the pump & carb assembly looks right. Going to pull the carb again this weekend and give it a more thorough cleaning -- overnight soak and compressed air.

 

[Marine Services of Las Vegas]

Keep in mind that an engine that is hard to start after reaching op temp may be a head gasket issue. A compression test will not always show this where as a leak down test will.

 

[rednwhite]

Thanks for the advice. I'll definitely keep the head gasket in mind.

The motor is starting right up after after soaking the carb overnight in pine-sol and some attention with compressed air. Must've been some varnished gas gumming things up. Carb looks like new after the soak

Now I'm getting some popping and backfiring. I may have inadvertently thrown the timing adjustment off. going to check with a light per the service manual tomorrow.

 

[flyingscott]

You do not have a head gasket on that motor. Your popping and backfiring is probably a lean sneeze. Open the low speed screw an 1/8 turn at a time until the engine runs smooth. Make the final adjustments when the engine is warm. Does your motor have the wire running from the carb to under the flywheel. If it does make sure it is not binding as that wire may advance the timing. This advice depends on which ignition your motor has one has the wire one will not. The wire if you have it controls the fast idle when the knob is turned. It does this by advancing the stator timing to increase the idle. The other ignition will have a short wire to the carb. Taking the carb off does not affect the tining setting. Make sure you do a link and sync.

 

[rednwhite]

Thanks, flyingscott. Pretty sure that I screwed the timing up . I, um, may have turned the idle timing adjustment thinking it was a simple linkage adjustment, thereby throwing the timing off. I was unable to find the original position, so I'll check with a light as soon as I get time. Completely self-inflicted

 

[flyingscott]

Unless you turned the small rod under the flywheel your timing is fine. Do a link and sync and adjust your low speed mix screw.

 

[rednwhite]

Update:

Was ready to give up and turn it over to a marine mechanic. Called a local mechanic who has great reviews online. He didn't think it would be fair to work on an engine this old at his rate of $120/hr. He did take the time to speak with me about the problem at length. He agreed that it sounds a carburetor issue and advised me that these carbs are extremely hard to clean after they get varnished -- said to either find a new carb or try an ultrasonic cleaner. New carbs are $450, but an ultrasonic cleaner at harbor freight is $65. Ran all metal carb parts and the fuel pump body through a couple of cycles on the cleaner, rinsed and blew with compressed air. Things were noticeably cleaner and there was a lot of small crap in the cleaner solution when done. Reassembled and it started right up. Adjusted the low-speed mix a little richer than 1.5 turns and made a minor idle timing adjustment and it's running great now in a trash-can of water.

Thanks for all of the advice on this thread!

 

[Big Gee]

Sounds like things have worked out well!

I've been looking at the HF ultrasonic cleaners. Which one did you get? What solution is used with them for carb cleaning?

 

[racerone]

Wow-----Folks are paying $150 / hr------Where ?-----I have to move to that nrighborhood

 

[rednwhite]

[duplicate post]

 

[rednwhite]

Oops. That should be $120/hr. Raleigh, NC area.

I got this cleaner: https://www.harborfreight.com/25-liter-ultrasonic-cleaner-63256.html and a 20% off coupon from hfqpdb.com. Used around a 30% solution if Simple green HD Pro (doesn't react with aluminum). Ran through 2 8-minute cycles for each side of the carb (had to flip it).