Merc 1998 125HP Max RPM's

[tjerzak]

Hi,I recently purchase a used 1998 125HP outboard for my 1977 18ft open bow Glastron. I have finally gotten to put some hours on it and it's running great and perfect for the boat. I have a 19 pitch prop but I don't know if I should step up to a 21. Does anyone know the RPM range it should be running at when wide open? I recall from my older Merc's 4800-5300 or so but I don't know if that applies to this one. I did open it up and it got to around 5100 then seemed to "miss-fire" so I quickly backed off. Is there any type of governor on the motor to keep it for over-reving?
It seems to be running very well except when I stop for 15 min or more I have to choke it to get it running again. I adjusted the linkage and the idle screw but it doesn't seem to help. It idles smoothy around 800 rpms.
I have a manual on order but I thought I would see if anyone can help sooner.
Thanks,
Tom

 

[Texasmark]

Re: Merc 1998 125HP Max RPM's

For a '94 4 cyl the book says 5250.

Some of the marine mechanics on here say that overreving that particular engine could result in a snapped crank.

Misfiring could be the overrev (PPM) limiter..that engine should have one..if so, sounds like yours is kicking in early or your tach isn't telling you the truth.

To ID it, look for a 1" or so potted module, held to the block/bracket with 2 screws having the following colored wiring entering/exiting: purple, brown, black wire with yellow stripe, and black

The black with yellow stripe should go to your ign modules to shut down triggers when you go too fast.

HTH

Mark

 

[tjerzak]

Re: Merc 1998 125HP Max RPM's

Thanks,
I'll check it out but that sounds like it was the limiter. I didn't check the tach that close after it skipped so I could have been around 5250. It sounds like I need to go to a 21 Pitch or maybe a 19 Cupped. Anyone have any experience with the Michigan Wheel Aluminum Vortex?
Thanks,
Tom