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Can't advance timing far enough on Mariner 115 2+2

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2PBC22

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I recently bought a 1990 Mariner 115 and tried to use it on the water today and ran into an issue. At idle, the timing is 2-4, right where it should be. When going to max throttle, the timing is only 16 BTDC. I cannot advance the timing anymore as the timing arm cannot move any further.

I've taken apart, and rebuilt the carbs. Replaced the fuel lines, and checked the spark on all 4 cylinders. Compression also tested between 115 and 120.

At max throttle, rpm was only about 3,000. The prop is a 19 pitch on a boat that weighed 2000 pounds loaded so I expected to see 35-40 mph. I was only getting about 25, and the boat was even hard to get on plane. I also removed the intake cover, and at full throttle, the butterflies were wide open and dumping fuel into all 4 cylinders. I got the standard rough running at about 1800 rpm where the lower 2 cylinders kick in, so I know they were activated at 3,000 rpm too.

How can I go about advancing the timing when the timing arm is already maxed?

Thanks!
 
I woud double check your tach and I would guess you are overpropped. Get the factory service manual for that motor that is a MUST. You shpuld also go to www.cdielectronics.com and find the troubleshooting info about your ignition. Those motors do have a tendency to have stator problems.
 
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Thanks Tom! The prop is a 13x19. Everything I’ve researched says the motor should have no trouble reaching max rpm with this prop.

I’ve looked through the factory service manual and nothing addresses the issue unfortunately.

And I don’t know if my tach is perfect, but at 1800 on the tach, the engine was running rough as it transitioned from 2 to 4 cylinders. This makes me think the tach is atleast close because this occurs at 1800.

I’ll be sure to check out cdi electronics.

Not understanding timing completely, but if I can only get 16 btdc at full throttle, when it should be 23, is that enough to impact the rpm?
 
You should not need to adjust timing it very seldom ever goes out. Takes something pretty catastrophic for that to happen. The high speed coils in the stator can fail. Before you adjust timing other things need to be checked. Changing timing is the last thing to look at.
 
You should not need to adjust timing it very seldom ever goes out. Takes something pretty catastrophic for that to happen. The high speed coils in the stator can fail. Before you adjust timing other things need to be checked. Changing timing is the last thing to look at. Did you ever hear this motor run right. If it has one have you checked the flywheel key. Do you have a factory manual.
 
I have the factory manual. It does have a flywheel key. I’ll check to make sure that is intact. When testing today, I used a timing light, and the idle was within spec, but not the max advance. I also tested all 4 spark plugs with the timing light to make sure they were firing, and made sure they would jump a 7/16” gap.

I’ve never heard the motor run right, I just bought it this spring. I guess I’m having trouble understanding why the stator could be bad and affect performance when I’m getting good spark. The only thing I can’t advance is the spark because of the limit of the throttle arm.
 
You never heard this motor run right. You need to start with the basics your factory manual has all the info you need. Trying fo change the timing is the last thing you need to do.
 
Had something similar happen to a three cylinder Merc: the trigger coil could not rotate enough to make full spark advance. I replaced it woth another and all was good. But on another three cylinder, the opposite happened: I couldn't rotate it enough to idle down all the way!

My conclusion: The factory trigger coils aren't manufactured very accurately.

I cured the latter problem by grinding more clearance in the top bearing holder. You might try that. You need a bunch more advance.

Jeff
 
A couple of questions i have how can to have a good hole shot if only running on two cylinders? Have you checked your timing mark with a piston stop tool for true TDC. Without that reference point your timing light is useless. If the carbs are opening the same time and all four plugs are sparking you should get fire on all four cylinders throughout the range.
 
kimcrwbr1 said:
A couple of questions i have how can to have a good hole shot if only running on two cylinders? Have you checked your timing mark with a piston stop tool for true TDC. Without that reference point your timing light is useless. If the carbs are opening the same time and all four plugs are sparking you should get fire on all four cylinders throughout the range.
Click to expand...
This posting is for a 2+2 motor they are designed that way. They idle on 2 cylinders up to 1800 rpm then the other 2 come on. They control that by not putting an idle circuit in the bottom 2 carbs. The ignition fires all 4 plugs all the time.
 
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