Prop question.

[87 Montauk]

I have a 17 foot 1987 Whaler Montauk with a 90 horse 1987 Evinrude on it. The prop that came with it is 13 1/2 X 17. I dinged it up pretty good and swapped in another I had. I cant read it but it looks like its 14 X 17 or 19. Is that enough difference to damage anything & is there an acceptable range of suitable props or should I stick with what came on it?
I understand clearly the danger of useing a lower pitch and over reving the motor but am uncertain of the dangers going the other way a little bit. My tach doesnt work.

Thanks,
Ken

 

[QC]

Re: Prop question.

Being below the WOT RPM range can be more damaging to the engine than over revving. There is simply no way to do this properly without a tach. With your previous WOT RPM we might be able to guess a little, but still there is risk. And without knowing the pitch you are going to the guessing game gets even harder. If it is a 17 then you should be OK. This assumes that you were OK before. If it is a 19, you could still be OK if your prior prop was reaching the higher end of the range. Just guesses though.

 

[steelespike]

Re: Prop question.

I would say that a 17 or 19 would be typical on boats the 90 might be found on normally.
It is a crap shoot you may have noticed the motor may struggle a little more with the 19 especially when you add weight.
If the motor is lugging it will be fairly obvious with poor performance and probably an increase in fuel use.
If it is lugging over time it can cause premature repair problems.