2000 200 2 stroke Yamaha stumbling 200rpm loss in choppy water-HEELPPP

Only120jman

Seaman Apprentice
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Nov 3, 2012
Messages
35
2000 Yamaha 200 V6 2 stroke Saltwater Series II- compression 110-112psi across 6 cylinders- carbureted motor- (non OX66)

So, starting from scratch, last year (7/15) i was taking a cruise one evening and (have never had an issue with motor-flawless performance) i hit a choppy part of the river and all of a sudden the motor drops power like its out of fuel(3/4 tank) drops like 800-1000 rpm and starts cycling between running good for a second then dropping rpms like its running out of fuel. I turn around and head back to ramp, take to local reputable certified yamaha dealer and describe issue. They change the fuel pumps and say "its running great"(on muffs albeit).. so i pick up the boat and take it out and its doing the same thing only its dropping(stumbling) 3-500 rpm in a chop for a few seconds then picking up and running ok for 1 or 2 secs. So i carry back and describe the deal and they say its the carbs need rebuilt. So i have them rebuild the carbs and they say its ready, so i pick it up... get out and run it and once i hit the chop(1'-1.5' waves) it starts again.. only its dropping 200 rpm for a sec and then jumping back up and running fine, then dropping 200 etc...stumbling enough to notice the loss of power- and i smell fuel. At this point i shut off the motor, pull the cowling and there's fuel dripping out of the bottom of the airbox/breather so i crank it and the fuel begins pouring out of the breather box... soooo i swing around and head towards the ramp, return the boat and describe everything and show a video clip of what its doing(including the fuel pouring from airbox/breather) starting to get a little frustrated. (each time i take boat back they put it in line and it takes a week to get the boat back).. i also ask them if it could be a coil pack or electrical and they say no, that all the coils checked out ok... they say i needle and seat was bad(after a fresh rebuild???) so they fix the needle and seat issue- i ask them to take the boat out and trial test it politely, which they do and also carry an aux tank. They return and say the problem is a crimped fuel line at the lower cowling inlet grommet(where all the lines enter the motor) well, i had them replace all the fuel line from tank to onboard filter on motor/external micron filter/bulb/fuel tank bulkhead fitting with check ball/pickup tube in tank/screen on pickup tube/...(all brand new stuff complete from tank to motor).. soooo, i didn't ask them to trial run after replacing all that because i figured that would do it... well, a week later i was able to take the boat out and it happens again... 200 rpm drop in chop. at this point i have my wife drive the boat and i start pumping the bulb while its stumbling.. at this point the added pressure (from the bulb being pumped) the engine picks up 300 rpm and runs awesome as long as I'm pumping the bulb.. so once the water slicks off everything runs great again..so i get the idea that I'm losing fuel pressure from lack of ?? vacuum? maybe? i get back to my house and double check everything the mechanic did (i am a decent mechanic but not an "outboard" mechanic) so i know enough to double check all the hose clamps and even put 2nd hose clamps on everything to ensure for secure fits.. go back to the river and same thing... 200 rpm drop. At this point i put my own idea in place, an inline fuel assist pump making 2-3lbs of pressure. wire it in with fuseable link and heat shrink and head to the river.. same thing... i pump the bulb and it picks up the pace and runs fine again..hit the chop and it drops 200 rpm again.. soooooo.. here we are a few months later coming up on a years worth of waiting and tinkering and i figured id run this story by the field of experts and see if this sounds familiar.. any ideas would be appreciated.. i am now considering an inline pump with a regulator and dialing the pressure to whatever a squeezed primer bulb would be (10-13lbs?) and seeing if that corrects it? or checking the float settings? again if it didn't run perfect when i pumped the bulb then id be thinking electrical.. but it straightens out once i pump the bulb.. I'm lost for fixes.. thanks again for your time.. any help is appreciated.
 

tommarvin

Ensign
Joined
Nov 22, 2015
Messages
999
I would take your boat to another certified Yamaha outboard mechanic,never go back to this place, this is not right even if you have to drive a little longer..
Stop the fuel from pouring out the air box before you start a fire.
Check the fuel pressure, you can rebuild fuel pumps you don't need a brand new fuel pump. I don't trust these guys, they should have fixed your motor a long long time ago.
Did they really rebuild all six carbs? And then say a needle and seat were bad ? REALLY Im not feelin it.
Check for loose vacuum lines, visually check everything on motor,check every inch of wire especially where the wire goes into connectors pull them hard..
Keep posting questions, this forum will help you fix your motor.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
from what all you have written , my guess would be an air leak between the primer bulb and the pumps if pumping the bulb makes it go away.
sucks air when under a vacuum, but when pressured with the bulb it stops the air leak.
if you look in the frequently asked questions section of the forum, find the testing fuel system.
it shows how to test pressures and for air leaks
 

firstcatch

Petty Officer 3rd Class
Joined
Jan 20, 2014
Messages
75
Have you replaced the VST filter? I know when it is time to change mine when I start having a problem with RPM's when I sit back into a swell.
 

Only120jman

Seaman Apprentice
Joined
Nov 3, 2012
Messages
35
Tommarvin-- everything I told you is 100% straight truth. No exaggeration, I actually like and trusted these guys, however after several trips back and forth and a lot of excessive money I just ran out of extra money. Plus the boat ran "good enough" to use. I just ran it through the chop and waited for the fuel to "catch up" and we'd be on our way smooth again. I'm still working on it... I'm gonna try to test for vacuum leaks.. Just strange it all happened at once, then got somewhat better. Now it's only 200 rpm surge.. Just strange.
 

Only120jman

Seaman Apprentice
Joined
Nov 3, 2012
Messages
35
from what all you have written , my guess would be an air leak between the primer bulb and the pumps if pumping the bulb makes it go away.
sucks air when under a vacuum, but when pressured with the bulb it stops the air leak.
if you look in the frequently asked questions section of the forum, find the testing fuel system.
it shows how to test pressures and for air leaks

Ok I'll get to that today. Ty so much everyone.
 

Only120jman

Seaman Apprentice
Joined
Nov 3, 2012
Messages
35
from what all you have written , my guess would be an air leak between the primer bulb and the pumps if pumping the bulb makes it go away.
sucks air when under a vacuum, but when pressured with the bulb it stops the air leak.
if you look in the frequently asked questions section of the forum, find the testing fuel system.
it shows how to test pressures and for air leaks

Btw we've swapped out 3 bulbs. Nothing changes it so far. I take this boat out 45+ miles it is so consistent. I just know when there's a chop I full trim it down to plow through. We went on a 110 mi trip last sat. I trust the motor, just would like for it to be spot on.
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,413
Had the same issue with my ocean pro. Only happened once I got below 1/4 tank.
I replaced all the fuel lines from the tank to the pump with no improvement. Removed the tank select and anti siphon valves and the problem went away.
By the looks of the anti-siphon valve, I'm guessing it was sticking.
 
Last edited:

Only120jman

Seaman Apprentice
Joined
Nov 3, 2012
Messages
35
Had the same issue with my ocean pro. Only happened once I got below 1/4 tank.
I replaced all the fuel lines from the tank to the pump with no improvement. Removed the tank select and anti siphon valves and the problem went away.
By the looks of the anti-siphon valve, I'm guessing it was sticking.

Yesr, I removed one and out an open on in and it didn't change anything, then out a new one in and it still does it.
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,413
Next step is to rig up a remote tank and see if the problem goes away
 

99yam40

Fleet Admiral
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Sep 7, 2008
Messages
8,851
did you look up the fuel testing I talked about on this site?
if so did you test to see if pressures or air is getting in during this problem?

You have a carbed motor,
it helps when you pump the primer bulb,
new primer blbs are not the only place a problem will show up.

You need to test things and then be testing also when the problem shows up to see if something changed.

also is there still fuel coming out of the carbs like you described before?
 

Only120jman

Seaman Apprentice
Joined
Nov 3, 2012
Messages
35
did you look up the fuel testing I talked about on this site?
if so did you test to see if pressures or air is getting in during this problem?

You have a carbed motor,
it helps when you pump the primer bulb,
new primer blbs are not the only place a problem will show up.

You need to test things and then be testing also when the problem shows up to see if something changed.

also is there still fuel coming out of the carbs like you described before?

Yesr, I did look up the fuel testing page. Very thorough article. I will test it as soon as I get the gauge and fittings together. When the fuel was running out of the airbox I carried it straight from the river back to them,(they had just rebuilt the carbs) and he found a seat that was blown out. (That was last year about midway through the repair cycles... I only mentioned the bulbs because I think I forgot to mention specifically that I had tested and replaced them in the original article. This weekend, I drained all the bowls(for possible water pockets?) and pulled the fuel filter(it has water separator) and it looked good. Took boat out and it's still doing same stuff. On calmer water it's great, passed a larger yacht and once I hit the wake it began to stumble momentarily, I pumped the bulb and it caught up and we went on our way.
Gonna try to do the fuel system vacuum test this week.
 
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