Mariner 15 2 Stroke running too fast!

LanceB · 05 August 2009, 00:06

Hello All,

I'm new to the forum & have looked through the post but can't find a reference to my particular engine issue. I purchased a Mariner 15M 1997 year 2 stroke recently - actually it was included in the sale of a Honwave T32 & Honda BF5 package. It was sold as not running when brought out for the spring this year.

I knew I was taking a chance on it but you have to sometimes I guess. I cleaned it up, changed the plugs, cleaned the fuel out & cleaned the filter.

It started first time so I was really chuffed & started pumping water after the thermosat opened up!!

The problem though is that it's actually running too fast - it doesn't seem to want to run at anything like tickover or slow speed even tough I turned the primer knob fully counter clockwise. The owners manual said screw the slow idle screw full in on the carb & then back it out 1.5 turns, which I did. Any other adjustment screws have a red paint on them to lock them in place I assume so I left them well alone.

Is there any adjustment anyone can suggest I try?

Thanks in advance

oujakov · 05 August 2009, 02:05

When you're playing with idle screw, does the motor respond (increasing rpms)?
Or does it start to respond only when the idle screw is more than 1.5 turns in?

1. It is possible the throttle might be stuck in the semi open position. See if the throttle cable is in fully closed "off" position. Try lublicating it with wd40 or similar.
2. If hasn't helped, take carb off and see if the butterfly can be freely be opened and closed. While you're at it, get the carb fully cleaned in the with the toothbrush and gasoline. Get you tire inflator running, set it up with the soccer ball inflating needle and get all jets and all possible channels air pressure cleaned.

LanceB · 05 August 2009, 09:22

Thanks oujakov for your advise - I had a thought about the slow idle srew this morning. The maunual said turn fully clockwise & then back out 1 1/2 turns.

The screw is slotted & I assumed 1 turn was 365 degrees from a point on the circumference of the screw. Was I right or is it just a 180 degree turn of he screw driver?

Could to many turns anticlockwise (out) be the cause do you think?

Will cerlook at cleaning the carb out as you suggest if it isn't jus a miss understanding of terms on my part.

LanceB · 05 August 2009, 09:29

Hope you got the idea - meant to say 360 degrees etc

Forums don't have spell check either of course!!! :-)

Bigmuz7 · 05 August 2009, 09:55

Quote:

Originally Posted by LanceB

Hope you got the idea - meant to say 360 degrees etc

Forums don't have spell check either of course!!! :-)

Yes it does .. top right of your post box its the ABC with a tick under it

.. wont help you with numbers though

oujakov · 05 August 2009, 12:27

Quote:

Originally Posted by LanceB

Thanks oujakov for your advise - I had a thought about the slow idle srew this morning. The maunual said turn fully clockwise & then back out 1 1/2 turns.

The screw is slotted & I assumed 1 turn was 365 degrees from a point on the circumference of the screw. Was I right or is it just a 180 degree turn of he screw driver?

Could to many turns anticlockwise (out) be the cause do you think?

Will cerlook at cleaning the carb out as you suggest if it isn't jus a miss understanding of terms on my part.

Idle screw is nothing more than the "fine throttle" at the closed position of the carb's butterfly. You screw the adjustment in - you're opening the throttle, means motor starts to run faster, and vise versa.
There is no "set" position for this idle screw. Play with it until the needed speed of the motor at idle "starts licking" your ear.
I've always cleaned my carbs with gasoline, disel fuel or kerosene.

Try doing something tonight and then post results.

LanceB · 05 August 2009, 14:33

Quote:

Originally Posted by oujakov

Idle screw is nothing more than the "fine throttle" at the closed position of the carb's butterfly. You screw the adjustment in - you're opening the throttle, means motor starts to run faster, and vise versa.
There is no "set" position for this idle screw. Play with it until the needed speed of the motor at idle "starts licking" your ear.
I've always cleaned my carbs with gasoline, disel fuel or kerosene.

Try doing something tonight and then post results.

Thanks for that - i'll see if I can try it tonight (depends if the rain holds off) & post results

Cheers

m chappelow · 05 August 2009, 15:03

could it be drawing air in, from loose nuts or a broken gasket on the carb where it mates to the engine ,

LanceB · 05 August 2009, 15:16

Quote:

Originally Posted by m chappelow

could it be drawing air in, from loose nuts or a broken gasket on the carb where it mates to the engine ,

Not sure but everything looks Ok. I'm going to give it another go tonight if possible & another good look over myself. May have to take it somewhere if not

AllenF · 05 August 2009, 16:26

when you adjust the screw rev the engine slightly then WAIT it takes a bit of time to use the fuel alredy there
1 turn is a full 360 but full in (to a pinch tight) then two out is a VERY good place to start from

LanceB · 05 August 2009, 17:56

Quote:

Originally Posted by AllenF

when you adjust the screw rev the engine slightly then WAIT it takes a bit of time to use the fuel alredy there
1 turn is a full 360 but full in (to a pinch tight) then two out is a VERY good place to start from

Thanks for the advise - I'm going to set it up now & give the suggestions so far reeived a whirl !!

Will post my results

LanceB · 05 August 2009, 20:42

Quote:

Originally Posted by oujakov

Idle screw is nothing more than the "fine throttle" at the closed position of the carb's butterfly. You screw the adjustment in - you're opening the throttle, means motor starts to run faster, and vise versa.
There is no "set" position for this idle screw. Play with it until the needed speed of the motor at idle "starts licking" your ear.
I've always cleaned my carbs with gasoline, disel fuel or kerosene.

Try doing something tonight and then post results.

I thought I'd cracked it when it fired first time & then I stopped & adjusted the idle screw on the carb & it was running much slower.

Stopped & adjusted again but wouldn't start - checked the fuel & stopped it up, cleaned & checked the plugs, checked & rechecked everything I knew but it wouldn't fire again!!

Bit deflated now but will try again Friday maybe...Ah well

m chappelow · 05 August 2009, 21:18

it could be also that the screw your adjusting has worn at the pointed end, an instead of being smooth has a ridge , it is some times caused by overtightening which then makes the fine adjustment all or nothing .

Turbodiesel · 05 August 2009, 21:49

I hope this attachment works. Have a read this is how you should do it.

Mixture screw should be screwed in and lightly seated and as a starting point take it out by 1 and a half turns. But you can fiddle it a bit to get them to run right!.

LanceB · 05 August 2009, 22:14

Quote:

Originally Posted by Turbodiesel

I hope this attachment works. Have a read this is how you should do it.

Mixture screw should be screwed in and lightly seated and as a starting point take it out by 1 and a half turns. But you can fiddle it a bit to get them to run right!.

Many thanks for the pdf

Timing light eh!!! perhaps I should stop at this point then as I don't have one of those..Sounds as though I need someone like youself on the case.

1 1/2 turns is what my owners manual said & this is what I had when it ran. What I don't get is that it was starting first pull & did again tonight then nothing at all even after going back to the 1 1/2 turns as before.

oujakov · 06 August 2009, 13:06

Quote:

Originally Posted by LanceB

Many thanks for the pdf

Timing light eh!!! perhaps I should stop at this point then as I don't have one of those..Sounds as though I need someone like youself on the case.

1 1/2 turns is what my owners manual said & this is what I had when it ran. What I don't get is that it was starting first pull & did again tonight then nothing at all even after going back to the 1 1/2 turns as before.

You can do ajustments while the motor is running, just keep your thingers off moving parts.

It looks like if you can start it, then timing is not the issue, as there is no load to the engine at idle. If you know factory setting for timing, I'd suggets to set it at that point for now. Timing could become an issue when you'll start runnung the motor on the boat.

Here what I thing is happening.

When you try firing up the engine, do you have the tiller arm throtle piosition on the "start" line or just fully closed (idle)?

It is is not on the start position, then it will not start (e.g. throttle butterfly is almost fully closed) as the air/fuel mixture is way to rich.

At first, your idle scre was way to much in, this was enough for throttle to be open and start the engine. Now, you seem to figure out how to slow down, but it wont start (as I understand).

Do this little test:

place the tiller throttle into the start position (a little bit open)
start the motor (pull coke out if the motor is cold)
idjust idle speed with the screw witht he motor running.

Keep motor running for few minutes. stop it and take the pugs out, as angin was only idling the plugs suppose to be darker colot then normal, dark chokolate, but not black. if they are black you either need to adjust mixture screw for little leaner.
You may also have out of spec spark plugs that may explain hard/impossible starts when warm. I'd put brand new plugs, just to eliminate the possibility that problematic plugs.

LanceB · 06 August 2009, 21:29

Quote:

Originally Posted by oujakov

You can do ajustments while the motor is running, just keep your thingers off moving parts.

It looks like if you can start it, then timing is not the issue, as there is no load to the engine at idle. If you know factory setting for timing, I'd suggets to set it at that point for now. Timing could become an issue when you'll start runnung the motor on the boat.

Here what I thing is happening.

When you try firing up the engine, do you have the tiller arm throtle piosition on the "start" line or just fully closed (idle)?

It is is not on the start position, then it will not start (e.g. throttle butterfly is almost fully closed) as the air/fuel mixture is way to rich.

At first, your idle scre was way to much in, this was enough for throttle to be open and start the engine. Now, you seem to figure out how to slow down, but it wont start (as I understand).

Do this little test:

place the tiller throttle into the start position (a little bit open)
start the motor (pull coke out if the motor is cold)
idjust idle speed with the screw witht he motor running.

Keep motor running for few minutes. stop it and take the pugs out, as angin was only idling the plugs suppose to be darker colot then normal, dark chokolate, but not black. if they are black you either need to adjust mixture screw for little leaner.
You may also have out of spec spark plugs that may explain hard/impossible starts when warm. I'd put brand new plugs, just to eliminate the possibility that problematic plugs.

Many thanks for your very comprehensive advise...really appreciate it

I'm certainly going to give this a try, probably wont be till Saturday now but I'll post my results.

Cheers

LanceB · 10 August 2009, 23:40

Quote:

Originally Posted by oujakov

You can do ajustments while the motor is running, just keep your thingers off moving parts.

It looks like if you can start it, then timing is not the issue, as there is no load to the engine at idle. If you know factory setting for timing, I'd suggets to set it at that point for now. Timing could become an issue when you'll start runnung the motor on the boat.

Here what I thing is happening.

When you try firing up the engine, do you have the tiller arm throtle piosition on the "start" line or just fully closed (idle)?

It is is not on the start position, then it will not start (e.g. throttle butterfly is almost fully closed) as the air/fuel mixture is way to rich.

At first, your idle scre was way to much in, this was enough for throttle to be open and start the engine. Now, you seem to figure out how to slow down, but it wont start (as I understand).

Do this little test:

place the tiller throttle into the start position (a little bit open)
start the motor (pull coke out if the motor is cold)
idjust idle speed with the screw witht he motor running.

Keep motor running for few minutes. stop it and take the pugs out, as angin was only idling the plugs suppose to be darker colot then normal, dark chokolate, but not black. if they are black you either need to adjust mixture screw for little leaner.
You may also have out of spec spark plugs that may explain hard/impossible starts when warm. I'd put brand new plugs, just to eliminate the possibility that problematic plugs.

Gave it another go on Saturday morning - no joy & thought it was probaby time for me to give it to someone else. Took it to the local marina & they are going to give it the once over..they recon that the carbs get mucked up by the varnish from the fuel flaking off when they are started again after a long period inactivity & this clogs the jets???

Hope they can get it running properly for me now

Thanks for all the helpful advise.

m chappelow · 11 August 2009, 00:07

Quote:

Originally Posted by oujakov

You may also have out of spec spark plugs that may explain hard/impossible starts when warm. I'd put brand new plugs, just to eliminate the possibility that problematic plugs.

just had this with a near brand new engine about 15 hours use from new ,would start first pull then after it had been running a few mins it ran rough and onto one cylinder and wouldent restart ,on removing the plugs and they both showed a good strong spark it wasent until a very close examination that the insulater ceramic on the tip was broken and could be slid up and down a fraction on one plug ,looking it at first time/ newish plugs that had a strong spark and were clean you wouldent have guesed that one was was at fault ,,new plug and it ran perfect .

oujakov · 11 August 2009, 12:16

Quote:

Originally Posted by LanceB

they recon that the carbs get mucked up by the varnish from the fuel flaking off when they are started again after a long period inactivity & this clogs the jets???

It used to be correct, where is leaded fuel from 30 years back would leave the residue inside the engine and it's systems.....but modern fuels are much cleaner and of a higher standard..I guess they wanted to say you have a dirty carb.