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115 Mercury 1997

R

RedHamil

New member
:confused:Looking for Experiences and advice on turning my 1997 Mercury 115 hp outboard from a 2 by 4 running cylinders into a 4 x 4 running cylinders.

As all who have experiences with this engine. The engine runs on 2 top cylinders when below about 2000 rpm and then kits in the two bottom cylinders when runs above about 2000 rpm.
The bottom 2 carbs are Identical to the top 2 carbs with the exception that the 2 bottoms carbs lack Idle screws.
Question,
Has anyone removed the 2 screws plugs and installed Idle screws allowing the bottom carbs to work at all rpm levels.
I would imagine the timing would need adjustment and all carbs would need to be tuned and synced.
any and all comments wlecome

Redhamil
 
If you are saying your motor is running on a 2cyl at a time, your motor has an ignition issue. It should idles with all cyl and WOT with all cyl. This motor is equipped with an accelerator pump. Make sure the diaphragm is not ruptured/leaky. How do do you determine that there are only 2 cylinders running???
 
qhn said:
If you are saying your motor is running on a 2cyl at a time, your motor has an ignition issue. It should idles with all cyl and WOT with all cyl. This motor is equipped with an accelerator pump. Make sure the diaphragm is not ruptured/leaky. How do do you determine that there are only 2 cylinders running???
Click to expand...

Motor according to Mercury is designed to run on only 2 cylinders firing a Idle, Below 2000 rpm. Then at approx 2000 rpm and above the motor runs on all 4 cylinders. To top rpm of approx 5450 rpm.

Other responses have noted that motor cannot be made to run on all 4 cylinders at Idle due to vibration issues.

Thanks for your response, sounds like I may have not been clear on the issue in my first post.

Rodger
 
Rodger,
As I understood your ad stated that your motor was idling with 2 cylinders and kicking into the other two cylinders instead of all 4 cylinders above 2000rpm. If it kicks into all 4cyl, it is normal for a 2+2 Mercury motor with 2 resistor built-in stator adaptor (I believe). I did rejet the bottom carburators once and the motor bogged. If your motor is idling with 2cyl and kicks into all 4cyl, leave it alone! If it only runs on 3&4 then it has an ignition issue! Is what what suggested. There isn't a single outboard motor 2 or 4stroke that I haven't worked on or rebuilt more than once!!
Take care.
 
qhn said:
Rodger,
As I understood your ad stated that your motor was idling with 2 cylinders and kicking into the other two cylinders instead of all 4 cylinders above 2000rpm. If it kicks into all 4cyl, it is normal for a 2+2 Mercury motor with 2 resistor built-in stator adaptor (I believe). I did rejet the bottom carburators once and the motor bogged. If your motor is idling with 2cyl and kicks into all 4cyl, leave it alone! If it only runs on 3&4 then it has an ignition issue! Is what what suggested. There isn't a single outboard motor 2 or 4stroke that I haven't worked on or rebuilt more than once!!
Take care.
Click to expand...


Many Tanks for your reply.
Motor does run on all 4 cylinders above the 200 rpm level.
Have found a loose Bullet connector coming from stator to coils. Mechanic has installed new connector.
Motor Has been winterized and is now stored for winter Will have to wait till spring to see if this repair has solve the issue.
Mechanic checked Throttle Cam and Pump accelerator, his determination is all is OK.
Next steps to Be determined IF motor still having ISSUES.

Thanks Again

Still looking for other Observations and Ideas for Possibilities for items to check.
 
What issues are you having? The bottom 2 carbs are different as they have accelerator pumps on them. I have had the accelerator pumps on them fail and start leaking. This causes the bottom 2 cylinders to start firing they start to idle very rough when that happens not pleasant. I would leave it alone because if you start to modify the motor it could cost you a motor. Your max RPM for that motor is 5250 not 5450. I also don't believe that carb has an idle circuit cast into it at all you would need to buy 2 top carbs.
 
There is an idle circuit on the bottom 2 cylinders.----------No adjustment and set at the factory.---------------The bottom 2 cylinders just get a wee bit of fuel and not enuff to fire.---------The wee bit of fuel is for cooling and oil to the bottom 2.
 
Thanks Flyingscott
Make long story short, here goes
Motor runs great to approx 3500 rpm then when going toWOT motor has sporadic instantaneous cut out, a milla second or so, dyes then back to life. Enough that skier can feel it and it is noticed with sound of motor change.
Have had wire harness from stator changed, carbs cleaned and synced, new plugs, new fuel line from tank to motor. Mechanic checked fuel pump accelerator and throttle cam, all ok.
Recently I was looking at wires bundle from stator and found a loose bullet connector, had this replaced when motor was being readied for winter storage, so cannot determine if this could have some bearing on the problem till spring when boat goes back in the water.
During all work at the shop motor performed great on the dyno with loads to WOT.
Anyway thanks for your input and would be grateful to any other ideas or suggestions to ponder during the winter and then check out in spring.
As for Carbs, all input has lead me to decide to leave as is and look for other electrical issues.
The cut out is so quick and intermittent that it is leading me down the electrical issue path.
One other issue is that when coming down from WOT to Idle after running across the water, the motor makes a rattling sound.
Motor idles smooth and great hole shot. the issue of cut out only happens after boat reaches plane and then trying to get up to full 5250 rpm.
You can see the cut out on the rpm Gage drops from about 5200 down to 4800.
flyingscott said:
What issues are you having? The bottom 2 carbs are different as they have accelerator pumps on them. I have had the accelerator pumps on them fail and start leaking. This causes the bottom 2 cylinders to start firing they start to idle very rough when that happens not pleasant. I would leave it alone because if you start to modify the motor it could cost you a motor. Your max RPM for that motor is 5250 not 5450. I also don't believe that carb has an idle circuit cast into it at all you would need to buy 2 top carbs.
Click to expand...
 
If you slow down quickly the prop will want to keep turning.------It will ratchet.---------Test this yourself with motor in forward and turn prop clockwise by hand.
 
RedHamil said:
Thanks Flyingscott
Make long story short, here goes
Motor runs great to approx 3500 rpm then when going toWOT motor has sporadic instantaneous cut out, a milla second or so, dyes then back to life. Enough that skier can feel it and it is noticed with sound of motor change.
Have had wire harness from stator changed, carbs cleaned and synced, new plugs, new fuel line from tank to motor. Mechanic checked fuel pump accelerator and throttle cam, all ok.
Recently I was looking at wires bundle from stator and found a loose bullet connector, had this replaced when motor was being readied for winter storage, so cannot determine if this could have some bearing on the problem till spring when boat goes back in the water.
During all work at the shop motor performed great on the dyno with loads to WOT.
Anyway thanks for your input and would be grateful to any other ideas or suggestions to ponder during the winter and then check out in spring.
As for Carbs, all input has lead me to decide to leave as is and look for other electrical issues.
The cut out is so quick and intermittent that it is leading me down the electrical issue path.
One other issue is that when coming down from WOT to Idle after running across the water, the motor makes a rattling sound.
Motor idles smooth and great hole shot. the issue of cut out only happens after boat reaches plane and then trying to get up to full 5250 rpm.
You can see the cut out on the rpm Gage drops from about 5200 down to 4800.
Click to expand...

I have this very same problem!!!!! You have described it to a T.......did you ever find a fix?????? I know this is an old post but I am hoping you see this and reply......Mike
 
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