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1988 Force 125 hp

waterbouy

New member
"Two weeks ago speed had dropp

"Two weeks ago speed had dropped from 38mph to 24mph. Just this week It dropped again to 9mph. I cleaned the carbs, and did a compression check. 145-150 on all four cylinders. Fuel bulb stays hard. Any ideas? Thank you."
 
"What are the rpms doing? do y

"What are the rpms doing? do you have a tach - speed in itself tells nothing - if the motor is turning 5000 rpms and you are only going 9 mph you may have spun your prop hub.

If the rpms won't get above 1000 rpms or whatever, that is an entirely different matter."
 
The boat does not have a tach.

The boat does not have a tach. But I know the rpm is down. when I start the boat the gearshift hi idle does not rev nearly as high.
 
"If your compression numbers a

"If your compression numbers are good then it can only be ignition or fuel.

May as well start with the ignition first. If you have or can beg/borrow a timing light make sure you have spark at each cylinder - if a couple cylinders are not firing that will definately put a damper on performance.

If your spark tests out ok, then start back at the gas tank and work your way to the carbs."
 
"No, not always. This has a Pr

"No, not always. This has a Prestolite ignition system. You will have 2 CDI packs that fire the 4 coils (2 coils per pack).

There is a diode in the CDI packs which effectively split it into 2 separate units (inside). So half of the CDI pack can go bad which would look the same as one bad coil. This can be checked easily by disconnecting the ground wire from that pack (it goes from the pack over the top of the motor, under the flywheel to a terminal strip on the other side of the powerhead). If you disconnect that ground and you get spark back, it is the pack that is bad, however that is not a work around. Without the ground connected there is no way to shut the motor down other than choking it out or running it out of gas.

It can be a bit confusing but lets see if I can give you some hints...

If you have NO spark on two plugs (but must be paired ie 1 and 2 or 3 and 4, but not 1 and 3 as an example) that would indicate a bad pack

If you have no spark on 1 plug it could be either a bad coil or a bad pack or a bad trigger (sensor).

No spark on any plug would most likely be a bad stator, but could be two blown packs.

These can be quite a pain to troubleshoot, but you don't want to go swapping out parts to try and find what is wrong. Those CDI packs sell for over 400 bucks a piece from Merc (although you can get them for half that in the aftermarket and even cheaper used - but used is always a gamble).

If your spark is intermittent - ie. sometimes it's fine but then it will miss, that is almost always the trigger (sensor).

Additionally, the wiring on these is pretty poor so check the main terminal strip (below the packs) to make sure everything is connected. The ends tend to bust off, particulary on the trigger wires (the 8 little wires on the far right of the strip)...

Hope this makes sense and helps a bit, I have spent many an hour chasing my tail with prestolite ignitions..."
 
"Thank you very much awsome in

"Thank you very much awsome info. I had to replace my tilt and trim motor on holidays. but the only one I could find is a 3 wire system. My boat is wired for two. Is there a way to make it work? I have the black connected to the battery ground. The blue to the up wire, it works. But the green does not."
 
Sorry for the delay in getting

Sorry for the delay in getting back to you - I will have to do some digging.

Your best bet may be to post another new message. Someone will probably know right off the top of their head.
 
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