Correct prop for 1980 Merc 90HP?

[Mnemonic]

I am bout to mount my '80 90HP on my boat, the motor did not come with a prop, the guy i bought it from said that he used a 21 pitch prop when he had it on his 18ft boat, but my boat is a 15', and I dont want to over/under power when it comes to the prop.<br /><br />Thanks!

 

[Chris1956]

Re: Correct prop for 1980 Merc 90HP?

Mneumonic, Selecting the correct prop is going to likely be a bit of trial and error. You will need a tach to "dial" it in correctly.<br /><br />BTW, I run a 21" pitch prop on my 16' speedboat with a merc 150 inline six motor.

 

[Mnemonic]

Re: Correct prop for 1980 Merc 90HP?

Thanx Chris,<br /><br />I was thinking about installing a tach, but I think i will buy a 21 pitch to see how that runs first... I need something to start with...