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Frustrating 2003 yamaha 50 hp TLR 2 stroke problem!

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zcarpman

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New to the forum but I am having a very frustrating issue that I cannot resolve on my 2003 Yamaha 50 hp TLRB 2 stroke outboard. The engine is on my 17 ft. Carolina Skiff flatbottom boat. We bought the engine backll in 2009 and ran it hard for commercial fishing purposes and it was tremendously reliable, never had one issue. The boat began having issues after one winter of sitting. The problem from the start has been the same, the engine starts up and idles awesome in the yard in neutral, revs up just fine, and seems like it is good to go. Once on the water under load, the engine still starts up and idles fine but immediately when throttled up begins to bog down and almost die unless you bring the throttle back down.

To me this seemed blatantly like a carburetor issue / fuel issue and the engine was not getting the fuel it needed. I've now become an expert on dismantling the carbs and cleaning everything. This spring I'm determined to get the engine back up and running well but it is proving difficult, this is what I've done so far:

1. Replaced all three spark plugs
2. Replaced inline fuel filter inside engine cowling
3. Replaced all fuel lines from tank to engine
4. Installed and replaced new water separator
5. Replaced engine fuel pump
6. Replaced cold start priming mechanism on second carb and rebuilt priming system
7. Bought carb rebuild it, fully disassembled carbs, chem dipped all metal parts over night
8. Rebuilt carbs with new kit
9. Scrubbed and cleaned all jets and parts related to carbs
10. put carbs back together and reinstalled

I blew out both jets and the carbs really looked fully cleaned when I put everything back together and I was feeling certain that the boat would finally run good. I dropped it in today with the priming system set to "oN" and the engine started first turn and sounded good. Went to throttle up, same issue, immense bog into almost die, into throttle down. I also, noticed that when the throttle is in gear, if I put my hand in front of any of the carbs to restrict the air flow , the engine perks up and sounds much better and runs stronger. As soon as I take my hand away, same problem. So, to me it seems that the mix is lean, but I have NO idea how that would be since the carbs aare fully rebuilt. Does anyone have any ideas? Maybe the reed valves? Head gasket? Electrical issue? Powercore? Do the carbs need to be retuned??? Anything would be much appreciated, cheers!


 
So i took it out the other day on the lake and ran it through a bunch of tests. Up to 1/2 throttle (10-12kts) on my Carolina skiff the engine sounds and pushes great. Once you start to get close to 3/4 throttle it starts to skip almostand run poorly. It won’t die at all just skips and doesn’t gain speed. If you pump the ball it doesn’t help at all. If you restrict airflow to the carbs it will die so the mix seems alright. One thing I did start to mess with is the mix screw on the top of all three carbs. These definitely effected the overall performance. It seemed every time I tried different settings it would run differently. I got it up to 16 kts and running a bit better by screwing the screw outwArd. Any ideas at all? I’m thinking maybe it’s a timing issue. Is the CDI marking “II” supposed to be lined up for full throttle ?? If so, it is not currently it hits the stopper at about 1/2 throttle. Maybe it’s a timing issue. Anyways attached is a video of the skipping. Any help would be great , going to pop the carbs off and go through again tomorrow. Maybe the reeds ??

https://drive.google.com/open?id=1gn...2Ehu5k1Ebk0_4_
 
You said that when you put your hand over the carb to restrict the air flow the RPMS picked up . I would say it is a fuel problem and you are sucking to much air from some where .Which will make it run lean. On some old Carb engines would increase in RPMS when you shut it down because it's a little rich .
You had the carbs off so I assume the gaskets are not leaking. Keep following your air to the engine. Check the intake manifold ,gasket and look for cracks even on the engine head . It's hard to find ,easier on a fluid leak. While the engine is running squirt heavy oil on areas and see if the rpms pick up a little. If not to hot try your finger if possible. Good luck
 
zcarpman said:
So i took it out the other day on the lake and ran it through a bunch of tests. Up to 1/2 throttle (10-12kts) on my Carolina skiff the engine sounds and pushes great. Once you start to get close to 3/4 throttle it starts to skip almostand run poorly. It won’t die at all just skips and doesn’t gain speed. If you pump the ball it doesn’t help at all. If you restrict airflow to the carbs it will die so the mix seems alright. One thing I did start to mess with is the mix screw on the top of all three carbs. These definitely effected the overall performance. It seemed every time I tried different settings it would run differently. I got it up to 16 kts and running a bit better by screwing the screw outwArd. Any ideas at all? I’m thinking maybe it’s a timing issue. Is the CDI marking “II” supposed to be lined up for full throttle ?? If so, it is not currently it hits the stopper at about 1/2 throttle. Maybe it’s a timing issue. Anyways attached is a video of the skipping. Any help would be great , going to pop the carbs off and go through again tomorrow. Maybe the reeds ??

https://drive.google.com/open?id=1gn...2Ehu5k1Ebk0_4_
Click to expand...
Did you ever get this fixed
 
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