need outboard help please!

[bunkrepair]

before i pull the plugs and watch it sink!

at full throttle it will build high rpm then fall on its face then slowly build rpms back up .

if i trim all the way down it will run decent if i trim it up it will not run full throttle without the rpms going roller coastering



if i hook up to a hose it seems to run great seems to only happen under load

i have a new
water fuel seperator
plugs
floats in carbs

any ideas thanks for any help

 

[TBI]

Sounds like a fuel delivery issue. Floats maybe?

 

[bunkrepair]

Sounds like a fuel delivery issue. Floats maybe?

there all brand new! and im not sure about you could adjust the float level, i was thinking maybe a week fuel pump?

i have noticed if you pump the primer ball up till its firm then run it for 5 minutes at say 2800 rpm it will lose its prime, well firmness it still has fuel in it just not full like was before engine started

 

[sergeantmike]

Fuel line not getting pinched when you trim the motor?

Tank have crap in it that may be sloshing around and hanging up on the fuel strainer?

Let's play with it tomorrow and isolate the probs. Bring a aux tank we can plug on to check that part.

We can also convert it to Jet Power with the old Olds and the "C" pump.

 

[TBI]

Go run it with someone in the back, when it'starts to fall on it's face, have them squeeze the bulb and see what happens?

 

[TBI]

Fuel line not getting pinched when you trim the motor?

Tank have crap in it that may be sloshing around and hanging up on the fuel strainer?

Let's play with it tomorrow and isolate the probs. Bring a aux tank we can plug on to check that part.

We can also convert it to Jet Power with the old Olds and the "C" pump.

Good thinking

 

[bunkrepair]

checked the pinching not happing

tbi would this happen if i had a cracked/broken/stuck reed?

 

[OCMerrill]

We can also convert it to Jet Power with the old Olds and the "C" pump.

Lets not get carried away now.

 

[bunkrepair]

Lets not get carried away now.

im thinking twin engines and pumps!

 

[KBS Engineering]

Assuming the fuel pump is working, most likely it is a crack or leak in a fuel line, allowing air into the system between the fuel tank and the fuel pump. This will allow proper fuel supply at light load, and allow air to be included to the fuel pump at high load conditions. Check your supply lines-or just replace them.

On a side note, old fuel tanks sometimes have scale or debris in them that is too large to make it thru the fuel pick-up line. At a heavy load the debris can clog the outlet to the pump and cause fuel starvation. Once the load is reduced, the offending debris falls back to the bottom of the tank waiting for the next time to cause a problem.
Best of Luck!!!

 

[sergeantmike]

"Lets not get carried away now."

Agreed... that much power would tear it apart!

Sean... no thread crapping Just me and O.C. funning...

We will sort this sluggish outboard problem out in the morning. Or maybe afternoon, depending on when you get your ass on the lake.

 

[TBI]

checked the pinching not happing

tbi would this happen if i had a cracked/broken/stuck reed?

When I have experienced broken reeds it would sputter and sometimes backfire through the carb on the cyl with the bad reed.... even at idle

 

[sergeantmike]

"On a side note, old fuel tanks sometimes have scale or debris in them that is too large to make it thru the fuel pick-up line. At a heavy load the debris can clog the outlet to the pump and cause fuel starvation. Once the load is reduced, the offending debris falls back to the bottom of the tank waiting for the next time to cause a problem."

Bring an aux tank.... clean one.

 

[bunkrepair]

"Lets not get carried away now."

Agreed... that much power would tear it apart!

Sean... no thread crapping Just me and O.C. funning...

We will sort this sluggish outboard problem out in the morning. Or maybe afternoon, depending on when you get your ass on the lake.

im gonna drain the tank first think make sure there no shit in there, then check for air leaks in the fuel lines

anybody know what the airfuel mixture screws should be set at 11/2 to 2 turns like a dirtbike more less i havent checked what they are at but will in the morning

 

[BMABITY]

Assuming the fuel pump is working, most likely it is a crack or leak in a fuel line, allowing air into the system between the fuel tank and the fuel pump. This will allow proper fuel supply at light load, and allow air to be included to the carb at high load conditions. Check your supply lines-or just replace them.

On a side note, old fuel tanks sometimes have scale or debris in them that is too large to make it thru the fuel pick-up line. At a heavy load the debris can clog the outlet to the pump and cause fuel starvation. Once the load is reduced, the offending debris falls back to the bottom of the tank waiting for the next time to cause a problem.
Best of Luck!!!

What he said.. I had a small crack in a fuel line once, changed everything except the cheap fuel line. Expensive mistake but hell I learned from it.

BTW, my boat was doing exactly what you claim.

 

[OCMerrill]

When I have experienced broken reeds it would sputter and sometimes backfire through the carb on the cyl with the bad reed.... even at idle

Right. That would affect running accross the board and even make it hard starting.

This is a fuel dilivery issue I think and I must remind that running a two stroke out of fuel or starving one for fuel can have some pretty severe consequences. Careful not to lean it out.

 

[TBI]

im gonna drain the tank first think make sure there no shit in there, then check for air leaks in the fuel lines

anybody know what the airfuel mixture screws should be set at 11/2 to 2 turns like a dirtbike more less i havent checked what they are at but will in the morning

I don't think I'd mess with them just yet - Try one thing at a time grasshopper

 

[bunkrepair]

What he said.. I had a small crack in a fuel line once, changed everything except the cheap fuel line. Expensive mistake but hell I learned from it.

BTW, my boat was doing exactly what you claim.

they are all new lines i replaced them personally maybe i have a bad connection somewhere between all the carbs and shit

 

[OCMerrill]

im thinking twin engines and pumps!

Yeah this has also been tried. Same top speed.

 

[bunkrepair]

Right. That would affect running accross the board and even make it hard starting.

This is a fuel dilivery issue I think and I must remind that running a two stroke out of fuel or starving one for fuel can have some pretty severe consequences. Careful not to lean it out.

starts great while cold one warmed up shes a little rough starting also but could be something with the air in the lines

 

[TBI]

Check the screen on the pump, also make sure all the bolts on the pump are tight but don't over tighten them

 

[bunkrepair]

alright ill have some updates by 8 am haha im gonna be up early fighting this thing

 

[TBI]

What year?

 

[WTMFA]

Make sure the fuel tank vent is clear.

 

[bunkrepair]

What year?

i believe a 79 but there the same from 77 to 81 i beleive

 

[sergeantmike]

It's 2011.... Yeeeesh!

Sean's 115 Merc is a fossil.

 

[TBI]

i believe a 79 but there the same from 77 to 81 i beleive

115hp correct?

 

[bunkrepair]

115hp correct?

yes sir, thnks for all your help!

 

[TBI]

yes sir, thnks for all your help!

Do you happen to have the serial #

 

[Classic Daycruiser]

I had my fuel level sensor replaced on one of our boats, and some rotted wood got into the tank before the new sensor was installed.

Fuel level sensor problem solved, created problems as you describe at high rpms, and when the tank get low. Mine had a belly fuel tank.

 

[TBI]

Passed my bedtime, find the serial number and I'll check back in the am :thumbsup

 

[Faceaz]

I would replace the fuel lines, it's cheap & the problems they could create could run you in circles - they can clog, crack, some old hose will swell & restrict the ID, etc. Check the pick-ups to make sure there's no clogs. Replace the primer bulb - those things can suck air. Since you've already rebuilt the carbs, pretty much everything from the tank to the engine.

 

[Letzgo]

I've had the exact problem you described twice now. once was on a jet (I know, I know) and it was a in-line filter that looked perfectly good and full but when boat was ran WOT for about 20 to 30 seconds it would start to do the roller coaster you described (starve for fuel). Changed a two dollar filter after many hours of trying to figure out the problem and problem solved.

The second time was on an outboard and the tank vented through the fuel cap. if you overtightened the fuel cap it would starve for fuel at WOT.

Good luck

 

[Phebus]

Asssuming it's a fuel delivery issue, if it was a fuel restriction prior to the priming bulb, it would suck the bulb down. Since it's losing bulb pressure I would look for a bad line or bulb itself.
I bet you end up going through the carbs though, and be very careful running it in a lean condition as you don't want to burn it up. The carbs are easy enough to go through, it's just removing the starter and disconnecting the linkage that's a pain in the ass.

 

[bunkrepair]

Asssuming it's a fuel delivery issue, if it was a fuel restriction prior to the priming bulb, it would suck the bulb down. Since it's losing bulb pressure I would look for a bad line or bulb itself.
I bet you end up going through the carbs though, and be very careful running it in a lean condition as you don't want to burn it up. The carbs are easy enough to go through, it's just removing the starter and disconnecting the linkage that's a pain in the ass.

carbs are cleaner than brand new ones i have rebuilt them all 3 times becuase the first time i just cleaned them, the second i replaced the floats and the 3rd time a float got stuck because the little spring came out of the top of the float,

there is vent on the aluminum tank, i believe it vents threw the lid style cap but here is zero to over tighten it,

the problem maybe where the fuel lines connects into the motor the little peiece there is a little sloppy but id have to do some digging to see if its leaking or something

thanks everyone for all your help im gonna go get my hands dirty so i can get on the water before 2 lol

 

[bunkrepair]

this maybe a retarded question,

should the priming bulb be before or after the fuel filter, currently it is before the filter because thats where it was located when i got the boat

 

[sergeantmike]

arty2:

 

[bunkrepair]

arty2:

can you resize and repost this picture please may help me figure this out

im pretty sure i have a fuel pump issues and a bad gasket m gonna go get a rebuild kit for it and see how the screen inside looks

 

[Tom Brown]

this maybe a retarded question,

should the priming bulb be before or after the fuel filter, currently it is before the filter because thats where it was located when i got the boat

My preference is to have the fuel filter between the bulb and the engine. That won't help the filter but the bulb will be less collapsed and will flow a touch better.

 

[sergeantmike]

"can you resize and repost this picture please may help me figure this out"

I dunno how.... it's a scanned snap shot. How does one resize a photo?

Keep trying on your end and gimme a call if you need a hand.

 

[bunkrepair]

replaced the bulb and rebuilt the fuel pump it was squirting a little fuel, idles better but still doing its shit on the top end

 

[Tom Brown]

replaced the bulb and rebuilt the fuel pump it was squirting a little fuel, idles better but still doing its shit on the top end

For all the problems I've had over the years with Mercury mechanical fuel pumps, these days I put in a Holley red, remove the bulb, and forget about it.

 

[bunkrepair]

For all the problems I've had over the years with Mercury mechanical fuel pumps, these days I put in a Holley red, remove the bulb, and forget about it.

tryed it again and then pulled the plugs seems to be a little and the rich/dark side

 

[TBI]

I'm thinking maybe the floats are out of adjustment?

 

[bunkrepair]

I'm thinking maybe the floats are out of adjustment?

could be how in the world do you adjust the floats on these things?

 

[Tom Brown]

could be how in the world do you adjust the floats on these things?

You have to bend the hinge arms.

Over the years, the floats don't float so well and they typically need to be adjusted down.

Your engine probably has foam floats. The early L6 outboard carbs had copper floats that would develop pinholes. You can tell when you shake them there is fluid inside.

Make sure they will float in gas before reinstalling.

I've got a manual that shows how to adjust L6 carb floats but it's at the lake. It's pretty easy, though.

 

[bunkrepair]

You have to bend the hinge arms.

Over the years, the floats don't float so well and they typically need to be adjusted down.

Your engine probably has foam floats. The early L6 outboard carbs had copper floats that would develop pinholes. You can tell when you shake them there is fluid inside.

Make sure they will float in gas before reinstalling.

I've got a manual that shows how to adjust L6 carb floats but it's at the lake. It's pretty easy, though.

they have all been replaced i think my top carb needs adjustment the most so ill start there and see if i get any results, how much adjusting does what? a 1/8 inch make a huge difference more less how much bending would be a good spot to start at?

 

[Tom Brown]

they have all been replaced i think my top carb needs adjustment the most so ill start there and see if i get any results, how much adjusting does what? a 1/8 inch make a huge difference more less how much bending would be a good spot to start at?

It's been a long time so I hope someone steps in and provides better information.

... but from what vague memory I have of the process, the floats need to rest about 3/16" up from the bottom of the bowl when the needles are seated.

It shouldn't take much bending at all.

 

[bunkrepair]

hum hum hum, this is gonna drive me to start drinking early today

 

[bunkrepair]

anyone know what the airfuel mixture screw should be at because they are all in different locations thats for sure one is about 2 1/2 other was 3 and the last was like 5