Prop pitch for 1987 Mercury Mariner 60hp 3 cyl? 4.2m inflatable rib

[CamaroMan]

Hi everyone, spun prop hub on first day out last week - ive pinned it now, but need some help on what pitch for my motor? According to my manual WOT rpm is low - 5300, gear case ratio is 1.64 : 1 - any ideas?

Ive played with the merc prop selector and i get mostly 14-15, and 13 in some cases (more weight).. Mostly fishing with a friend, and skiing with 3 aduts on board..

Pre ordered a 13, and 14s sold out here - so can also get a 15..

I would like to save some fuel during transit, and think the 13 will def burn more fuel.. whereas the 15 will give better economy - however the holeshot might be a little lost on 15..

A plus is the 2 stroke has good low end torque, and the boat is powered on the high side - many folks use a 30-40-50 with 60 being about the max..

Thanks all - I have to decide by monday tuesday latest!

 

[Sea Rider]

Is it a center console Rib with tach installed ? usually 4.20 Mtr Ribs are rated for max 40-50 HP. What does tech plate say if having one, which brand is it ? You should always test delivered prop with a tach at wot lightly loaded on flat calm waters. Check max achieved wot rpm and then go from there selecting a prop that puts that OB near max wot range.

How was water performance with current prop ? fishing with friend and skiing with 3 up is a complete different scenario, probably will need 2 props for that if wanting running top.

Anyway whichever prop you choose will need to test it with a tach, then go from there maximizing a prop to suit best your boating needs. Being a Rib a light combo you can achieve as much as + 500 wot revs with one less pitch size.

Happy Boating

 

[steelespike]

You should read the stickies at the top of the prop forum.
Get us your present lightly loaded wot rpm and gps speed.
My info indicates 5000 to 5500 wot rpm.
Generally lower motor rpm (higher pitch)doesn't necessarily.mean better mileage.
If you think about it more pitch actually makes it harder for the motor to perform.
Slower hole shot more sensitive to added weight
May struggle to maintain plane at reduced throttle.
May or may not deliver wot top speed.
Motor needs to rev freely within its rpm range.