Lowelife2003
Recruit
- Joined
- Sep 22, 2024
- Messages
- 5
Maybe someone will know more than I do about this problem . ( Like a experienced Yamaha tech )
1 2003 50 hp TRLB ran perfect last trip then parked in a field and sat for 11 years not winterized or fuel drained or anything !
2 replaced fuel tank , fuel line & primer bulb , engine mounted fuel filter, fuel pump, COMPRESSION 130 ON ALL , removed 3 carbs disassembled and found carb # 3 bottom carb the worst main jet blocked with crud and had to drill out hole with small bit. Soaking in chem dip and ultra sonic wouldn't remove the hardened crud. Note I was able to remove pilot jets on all 3 but the bottom main jet ( 130 size ) is stuck , not even penetrant or heat would free it. So it went back in the sonic cleaner for another hour.
3 Now the prime start system, the plunger on the solenoid was stuck in the bore and separated from the electrical portion ( they come apart ) and can be be snap back together. I tested ohms @ 3.2 which is in spec . next applied 12 volts for 6 minutes and plunger extended . Note when engine was idling I had 6.1 volts on blue wire ? I know it requires 12 but maybe because of idle speed its low. This device has 3 positions for fuel NORMAL , OPEN , CLOSED red level on front of carb.
4 I reused the floats & needle & seats , the seats can hold 10 psi in the closed position so they work. Next I blew out all the small fuel lines going to each carb and made sure fuel flowed from the carb lines using pressure from primer bulb. I can hear the fuel filling the bowls as I prime system. once full the bulb becomes hard. ( using fresh 89 octane fuel with Stabil in it ) Now on muffs in driveway to start it I have to switch prime start to OPEN mode for about 1 minute the to closed position . The engine will fire up quick and idle nice now. I'm curious if 2 stroke engines run better in the lake or a tank because of exhaust back pressure ? My theory is they do and I always think it sounds better in the lake than on muffs .
5 Now the interesting part once in the lake the engine fired right up and idled smooth I let it run for 30 minutes then switch the prime start to normal thinking it would be warmed up by then. It died ! restarted in fuel closed mode and it continued to idle.
Next put into gear and it ran pushing the boat about 3 or 4 mph then when trying to get on plane it bogs down and wont get on plane ! One time I was able to drive through it and get on plane. So with 2 people operating the boat I can sit by the engine and when we get to mid range and its shuddering I place half my hand over each carb . The top and middle carb had NO improvement in performance but the bottom carb ,, it immediately sounded better and allowed the engine to take off and reach top speed. So once through mid range WOP runs like a new engine Idle is fine except the " Prime start " system isn't working normally.
Now from my basic understanding of prime start its designed that in event of failure the RED LEVER can be used to by pass the system , how ever I would think once warmed up I should be able to run it in normal operation mode ?
Next I removed the carbs and drilled out CARB # 3 ( bottom ) main jet to remove the emulsion tube suspecting its tiny side hole to be clogged ? I found all of them open due to ultra sonic cleaning I suspect and was disappointed that I still have NOT located the lack of power taking off. The engine also has brand new NGK spark plugs
I now think once I get a replacement jet for the destroyed JET in carb # 3 I'm going to test on the lake this Saturday . I suspect a possible air leak between the carbs and reed plate but has no reason to suspect this its just I'm running out of options.
I have ordered brand new carbs to from Yamaha to be delivered Friday as a last resort but if this can be fixed without that expense I would much prefer that.
i also want to check voltage above idle on the blue wire to P/S system as @ idle its only 6 volts, I check the throttle linkage and ign time on the CDI box ( Mitsubishi ) and it appears normal which it should be since it wasn't messed with.
I went to a dealer to ask for help but it was quickly apparent that they had no one skilled in 2 cycle engines plus no one had any factory or UTI marine training. So I took the boat home.
Update I found the o ring on the aux fuel pump inside the Prime start was leaking slightly ( I bought 2 brand new Yamaha factory carbs and tested the old vs the new.
I installed the new carbs yesterday and started the engine on a hose in the driveway. While idling I am only measuring 6.5 volts on the blue wire feeding the Prime start solenoid. I increased engine speed to around 1500 but no change in voltage. I do not have the service manual or wire diagrams for this engine. The charging voltage @ battery is 14.5. Today Im going to see if it will get on plane in a normal fashion.
I'll update later as this is really frustrating and I have never had so much trouble from a 2 stroke. I'm a master certified Automotive tech but only school of hard knocks 2 stroke experience. So to be clear this engine has 3 carbs each is different slightly I replaced the middle and bottom carbs only with new Yamaha carbs. The top one is original equipment. I could have probably saved the middle and bottom but it would take 3 weeks to get the Jet and rebuild parts for prime start.
Donald TIA
1 2003 50 hp TRLB ran perfect last trip then parked in a field and sat for 11 years not winterized or fuel drained or anything !
2 replaced fuel tank , fuel line & primer bulb , engine mounted fuel filter, fuel pump, COMPRESSION 130 ON ALL , removed 3 carbs disassembled and found carb # 3 bottom carb the worst main jet blocked with crud and had to drill out hole with small bit. Soaking in chem dip and ultra sonic wouldn't remove the hardened crud. Note I was able to remove pilot jets on all 3 but the bottom main jet ( 130 size ) is stuck , not even penetrant or heat would free it. So it went back in the sonic cleaner for another hour.
3 Now the prime start system, the plunger on the solenoid was stuck in the bore and separated from the electrical portion ( they come apart ) and can be be snap back together. I tested ohms @ 3.2 which is in spec . next applied 12 volts for 6 minutes and plunger extended . Note when engine was idling I had 6.1 volts on blue wire ? I know it requires 12 but maybe because of idle speed its low. This device has 3 positions for fuel NORMAL , OPEN , CLOSED red level on front of carb.
4 I reused the floats & needle & seats , the seats can hold 10 psi in the closed position so they work. Next I blew out all the small fuel lines going to each carb and made sure fuel flowed from the carb lines using pressure from primer bulb. I can hear the fuel filling the bowls as I prime system. once full the bulb becomes hard. ( using fresh 89 octane fuel with Stabil in it ) Now on muffs in driveway to start it I have to switch prime start to OPEN mode for about 1 minute the to closed position . The engine will fire up quick and idle nice now. I'm curious if 2 stroke engines run better in the lake or a tank because of exhaust back pressure ? My theory is they do and I always think it sounds better in the lake than on muffs .
5 Now the interesting part once in the lake the engine fired right up and idled smooth I let it run for 30 minutes then switch the prime start to normal thinking it would be warmed up by then. It died ! restarted in fuel closed mode and it continued to idle.
Next put into gear and it ran pushing the boat about 3 or 4 mph then when trying to get on plane it bogs down and wont get on plane ! One time I was able to drive through it and get on plane. So with 2 people operating the boat I can sit by the engine and when we get to mid range and its shuddering I place half my hand over each carb . The top and middle carb had NO improvement in performance but the bottom carb ,, it immediately sounded better and allowed the engine to take off and reach top speed. So once through mid range WOP runs like a new engine Idle is fine except the " Prime start " system isn't working normally.
Now from my basic understanding of prime start its designed that in event of failure the RED LEVER can be used to by pass the system , how ever I would think once warmed up I should be able to run it in normal operation mode ?
Next I removed the carbs and drilled out CARB # 3 ( bottom ) main jet to remove the emulsion tube suspecting its tiny side hole to be clogged ? I found all of them open due to ultra sonic cleaning I suspect and was disappointed that I still have NOT located the lack of power taking off. The engine also has brand new NGK spark plugs
I now think once I get a replacement jet for the destroyed JET in carb # 3 I'm going to test on the lake this Saturday . I suspect a possible air leak between the carbs and reed plate but has no reason to suspect this its just I'm running out of options.
I have ordered brand new carbs to from Yamaha to be delivered Friday as a last resort but if this can be fixed without that expense I would much prefer that.
i also want to check voltage above idle on the blue wire to P/S system as @ idle its only 6 volts, I check the throttle linkage and ign time on the CDI box ( Mitsubishi ) and it appears normal which it should be since it wasn't messed with.
I went to a dealer to ask for help but it was quickly apparent that they had no one skilled in 2 cycle engines plus no one had any factory or UTI marine training. So I took the boat home.
Update I found the o ring on the aux fuel pump inside the Prime start was leaking slightly ( I bought 2 brand new Yamaha factory carbs and tested the old vs the new.
I installed the new carbs yesterday and started the engine on a hose in the driveway. While idling I am only measuring 6.5 volts on the blue wire feeding the Prime start solenoid. I increased engine speed to around 1500 but no change in voltage. I do not have the service manual or wire diagrams for this engine. The charging voltage @ battery is 14.5. Today Im going to see if it will get on plane in a normal fashion.
I'll update later as this is really frustrating and I have never had so much trouble from a 2 stroke. I'm a master certified Automotive tech but only school of hard knocks 2 stroke experience. So to be clear this engine has 3 carbs each is different slightly I replaced the middle and bottom carbs only with new Yamaha carbs. The top one is original equipment. I could have probably saved the middle and bottom but it would take 3 weeks to get the Jet and rebuild parts for prime start.
Donald TIA
