mercury 175 sportjet full rpm trouble

[hockeyfan514]

I just got my rebuilt engine running with break-in fuel and went through about 30 gallons. It idles great, midrange is good, but it wont go over 4700 rpm. I have new boyesen reeds, carbs are cleaned out, throttle linkage lets the throttle plates open completly, and the timing was just done by the dealer. What could cause an engine to not reach full rpm? The boat before it broke went to around 5600 rpm.

[mmb]

I have the same exact problem except mine is only going to 4200 rpms....... went to 5800 before the rebuild.........

[mmb]

well looks like number 2 and 6 are not firing..... I am changing the coils right now (I have new igniton boxes and stator)

Is it possible that the trigger is the problem? since 1 coil is out on each bank? I just had the stator replaced and not the trigger......

[blazer01]

well looks like number 2 and 6 are not firing..... I am changing the coils right now (I have new igniton boxes and stator)

Is it possible that the trigger is the problem? since 1 coil is out on each bank? I just had the stator replaced and not the trigger......

i could be wrong but 2&6 get there fire from the same power pak box. i find it kinda hard to believe that 2 coils went bad at the same time

[mmb]

Im sorry it was 3 & 6...... Middle on the left and bottom on the right..... Cylinder on each bank is not firing

[blazer01]

have you checked for any loose connections grounds etc?? i believe there is a way to check the trigger with a meter i dunno how thoe

[mmb]

Yeah I went over the grounds and unpluged/repluged all connections. The coils didn't change anything. I am going to order a trigger - there was something in the manual about two coils not firing on opposite banks is usually the trigger.........


It's the only thing left to change so hopefully it works out!!!

[sschefer]

Yeah I went over the grounds and unpluged/repluged all connections. The coils didn't change anything. I am going to order a trigger - there was something in the manual about two coils not firing on opposite banks is usually the trigger.........


It's the only thing left to change so hopefully it works out!!!

The trigger has three coils. There are two opposing magnets in the center hub.

Heres the trick - Write it down:

1 2 3
4 5 6

See, trigger coil #1 supports cylinders 1 and 4, #2 supports cylinders 2 and 5 and #3 supports 3 and 6.

I believe you said you lost fire to 2 and 6. That would be on the outer switch box. You can check the trigger voltage at the switchbox it should be around 4vac. Without a DVA adapter for your multimeter you would read around 2 volts.

This check requires a DVA adapter for your mulitmeter. --- Start the engine and read the voltage at the + terminal of the coils. A reading of less than 190 volts usually indicates a stator problem. No voltage could be trigger but if the other cylinder that the trigger supports has voltage you can eliminate the trigger and the only thing left is the switchbox. In your case I would be swapping it out for a known good one.

Your lucky.. Whenever one goes on me it always seems to be the inner and I have un-do all those dang terminals...LOL...

[mmb]

It was cylinder 3 & 6 that was not firing and from your post it is definatley the Trigger!!!

Thanks for the help!! What the best way to get the flywheel off? Do I have to buy the special tool?

[sschefer]

It was cylinder 3 & 6 that was not firing and from your post it is definatley the Trigger!!!

Thanks for the help!! What the best way to get the flywheel off? Do I have to buy the special tool?

Whoops sorry, didn't see your correction to 3 & 6. Yes you need a special tool. I don't think Jay Smith is selling them anymore but ask him. If not you can get the correct one by calling Pro Marine. There number is on their website at www.promarineusa.com (http://www.promarineusa.com).

DO NOT try to use an automotive puller, you will damage the flywheel or crankshaft.

[mmb]

I changed the trigger and set the timing.... Took it out on the lake and it is a rocket ship again!! 5600 rpm!!!

Thanks sschefer & Scream & Fly!!!