mercury 90HP lower unit gear ratio

[johnnywood]

I just bought a boat with this 1989 90 h merc 3cyl. serial number B208699. I think the lower unit was replaced. Is it possible to have the wrong gear ratio? I have no top end and have played around with prop pitch to no avail. PLEASE HELP!!!

 

[JUSTINTIME]

Re: mercury 90HP lower unit gear ratio

what is wot rpm?

 

[Silvertip]

Re: mercury 90HP lower unit gear ratio

Recommended WOT rpm is 5500. Lower unit gear ratio is 2.4:1. Make sure the throttle plates are perfectly horizontal in the carb bores with the throttle full open. If they aren't, you need to do a link & sync procedure. You need a service manual for this.