Re: 1983 115 power tower mercury
Tough question, it all depends on how well the motor runs, the weight of the craft, an so on.
Check compression, spark, run good fuel with a quality oil and see how it runs with that prop.
Repost with WOT rpm and speed and go from there.
Chances are that prop has been fine for the last 25 years and still may be fine, then again, it could have been wrong all this time, the only way to know is try it and find out, it should be close.
