2 Stroke Outboard Engine troubles low speed burp/thump.

kytooner

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Jul 11, 2021
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Ok motor sat for 10 years, started and was running great for a motor that sat for 10 years. But now as the gunk must be breaking free it started as slight bog on low speed acceleration and occasional burp in neutral. The burp was the most concerning. Only noticed in idle but every time it happened it was like the motor was shifting into gear then a slight oil or gas discharge. This was not a popping like I'm use to hearing in a 2 stroke with carb problems but more physical. All I can describe is like thump and I felt engine was going into gear. So I put new plugs in it and some sea foam in gas. That was probably a mistake in hind sight. The burp is still happening at idle and now what was sluggish in low speed has moved to falling apart in the mid range. Full throttle seems to do ok and idle does ok. Maybe more than one issue going on. Any Thoughts on the burp/thump in idle? (only noticed in neutral but maybe it's happening in idle forward and I don't notice. It does only seem to happen after running for a few minutes.

Other things I notice seems to be going through more fuel than I would expect. 20' pontoon driving for 1 hour eats 7 gallons of gas but maybe that's normal. Only achieves about 4200-4500 rpm don't know exactly as the tach only works up to 3800. Top speed at between 18 to 20 mph depending on how many passengers but that is about what I would expect. Motor had NGK BU8H spark plugs but they were not listed anywhere as being applicable so I went with what a Merc dealer told me was the right plug.

I can't even get an appointment for Mechanic they just say call me back in 6 weeks we are booked up. I say no problem how about we make an appointment for 6 weeks. No just call me back and well see if we can work you in.

So I sit here and think should I just order new carbs, aftermarket carbs, rebuild the existing carbs. I'm intimidated with multiple carbs and setting the timing. Seems like I recall that it never felt like the carbs were properly timed from the prior marine mechanic 10 years ago.

Can I access and change the fuel filter without removing the carbs?
Thanks for any thoughts and letting me ramble.
 

kytooner

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Can I do any damage by replacing fuel filter and and spraying some carb cleaner (chlorinated) into carbs in hopes that it gets me through when mechanics get slow enough to be willing to work on my old motor.
 

racerone

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Dec 28, 2013
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38,550
Some will argue.-----That motor should run a lot smoother.-----Start with a compression test.----Post your numbers.
 

kytooner

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Jul 11, 2021
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Can't argue with that. Ok compression test it is. Will do it this coming weekend.
 

kytooner

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Jul 11, 2021
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120, 118, 120 Throttel open, safety kill off, One spark plug out at a time. Put the 10 ur old BU8h spark plugs back in And it’s back to running the way it was Which is Farley even throttle response. We will see if temporary I suspect the 10-year-old fuel filter it’s truly the blame
 

kytooner

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Jul 11, 2021
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OK short-livedOn the way back rough waves Mid throttle it would seem to lose power but if I went full throttle it would recover
 

kytooner

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Jul 11, 2021
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Noticed a little water in bottom of engine under cowl, both occurrences have happened after running through some rough water. Any chance moisture affecting electronics. Doesn't' seem like issues since when I go into full throttle issues clears up but if I go back down to mid throttle the issue starts up again.. Holding throttle steady rpm slows down as does boat. It might clear up a bit or get even slower. If I give it full gas issues clears up. Was not doing this issue on the drive to lunch 40 minutes plus of going from Idle to mid throttle to full throttle and it worked great. Boat sat for lunch about 45 minutes no problems starting. And on the way back 20+ minutes fine, after hitting the roughest water issue started.
 

Faztbullet

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Mar 2, 2008
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15,931
Pull the carbs and clean em with new gasket kits. Replace all fuel lines from tank to carbs. You have debris floating in fuel system
 

Sea Rider

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Sep 20, 2008
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Out of curiosity, how did you started the motor up after sitting for such long 10 years of storage ? That motor once carbs are fully clean should benefit going for a long decarbon process through the carb's throats with whatever decarbonizer brand is available, the motor will run much smoother soon after returning from a 15 minute wot run as if stealing the combo...

Happy Boating
 

kytooner

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Jul 11, 2021
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35
Thankyou for the input floating stuff in fuel system makes sense.

After 10 year hibernation I put some straight 2 stroke oil in pistons let sit. Emptied fuel tank, put some fresh fuel in it, emptied again turning it upside down and shaking all the crud out that I could. Bought a fresh battery, put in fresh fuel, and it started. It starts on nearly the first attempt everytime. Don't need to pump the ball and choke only if it's been more than week.

Should I feel guilty?

Yes my plan is to find mechanic willing to rebuild carbs, fuel pump, replace all oil and fuel lines, and I might look into putting one of the those spin on fuel filters for easier filter change in the future.
 

kytooner

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Jul 11, 2021
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Everyone tells me to call them back in 3 weeks I know they will then be swamped with winterization. So I guess I'll have to do myself. Can someone point me to best carb rebuild kits and where to get them? And what size tubing is needed for fuel and oil lines?
 

kytooner

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Joined
Jul 11, 2021
Messages
35
Everyone tells me to call them back in 3 weeks I know they will then be swamped with winterization. So I guess I'll have to do myself. Can someone point me to best carb rebuild kits and where to get them? And what size tubing is needed for fuel and oil lines?
Scratch that finally got an appointment in a week and half. Woot woot, going to replace fuel pump, clean rebuild carbs, replace fuel and oil lines, check and clean fuel intake. Anything else one should have them do?
 
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