Yamaha help

[the lackster]

Hello, looking for help with my 70 tlrr. It cranks and idles without an issue whatsoever but when i start easing into the throttle it bogs down and will cut off if i keep pushing it. It doesn't sputter or skip, it just falls on it's face but if i back off the throttle its fine. Once it has ran for a while it will finally decide it wants to run and will get on plane and run wide open, seems to be worse in cooler temps. I have pulled the carbs for cleaning and ordered new parts. I did notice when i took the bowl off the bottom carburetor that the rubber plug was not in the pilot jet hole. Could this cause an issue? Either way i have the replacement in the mail. Also when the boat is in neutral should the timing indicator on the side of the motor be lined up on 1 of the 2 lines or in between? I am extremely novice with boat motors and looking for help. I attached a picture of the plugs if this helps with a diagnosis. These are new plugs that have been ran a couple times on short trips. I am hoping the clean carbs will make an improvement but wanted to see if there could possibly be another issue that i might need to be working on while waiting on parts to ship. ANY help would be greatly appreciated!!!

So far i have recently
- replaced tank to motor line "bulb included"
- cleaned fuel strainer and bowl
- drained and cleaned fuel tank
- new NGK spark plugs " gap checked by Yamaha dealer"

 

[the lackster]

Clean the carb.....secondary jet is stopped up...

Secondary as in pilot?

 

[geezer]

I misread your post...I was thinking the small single cylinder motorcycle...

 

[geezer]

I’m not a boat mechanic, but those plugs look like it’s running way rich....

 

[StuP]

I’m not a boat mechanic, but those plugs look like it’s running way rich....

I agree, but if you want to evaluate mixture by the plug color you really need to cut the engine while it's running at the throttle / load condition you want to check, (ie full throttle etc). If you idle back to the dock, idling mixture is what you'll see.

Sounds like a carb problem, based on the description. Does it have a manual choke ? If so, does it accelerate better when cold if you add some choke or does that make it worse ?

 

[the lackster]

I agree, but if you want to evaluate mixture by the plug color you really need to cut the engine while it's running at the throttle / load condition you want to check, (ie full throttle etc). If you idle back to the dock, idling mixture is what you'll see.

Sounds like a carb problem, based on the description. Does it have a manual choke ? If so, does it accelerate better when cold if you add some choke or does that make it worse ?

It has the prime start fuel enrichment on the side of the second carburetor. I have ran it in auto and in a close position and it acts roughly the same. If i turn it to the emergency fuel enrichment it will flood pretty quickly.

Also this motor is running off 50:1 premix it does not have the precision blend on it.

 

[the lackster]

I’m not a boat mechanic, but those plugs look like it’s running way rich....

That was my thought as well. I had a fuel starving issue before but its not acting like that. If anything its acting the opposite.

 

[sniper22]

Its gotta breath to run. Check intakes and vacuum lies

 

[StuP]

That was my thought as well. I had a fuel starving issue before but its not acting like that. If anything its acting the opposite.

It sounds like you want to start with getting the carbs cleaned thoroughly, or rebuilt. So easy to get a leak or a tiny blockage.

 

[the lackster]

It sounds like you want to start with getting the carbs cleaned thoroughly, or rebuilt. So easy to get a leak or a tiny blockage.

carbs are taken apart and new parts should be here tomorrow. I couldn't see through one of the pilot jets after i sprayed carb cleaner up in it. Stuck a piece of 50lb test line up in there and it appears to be clear now. Hopefully this was one of the issues.