Which prop should i buy?

Jason calleja · 19 September 2012, 20:16

Hi all i would like which propeller shall i buy for my mercury 60hp 4 stroke EFI. I have a 16ft rib that it is running with an aluminium 10.1/2 x 14 pitch and it is giving me 32knot at 6000 at full open throttle and full trim with 2 adults and some water and fuel around 200kg. I wish to upgrade to a stainless steel prop i would like to know what will be the right pitch and if i would buy 3 or 4 blade i was looking at the trophy sport and vengeance propellers. What do you think? Thanks Jason

Locozodiac · 19 September 2012, 23:18

What's max rpm factory state for that engine, probably you are at the limit of 6 K rpm at wot, if so, whay would you want other prop, more speed, better hole shot ? If 6 K is the max, probably you are already over reving when boating lightly loaded and solo.

Happy Boating

lightning · 20 September 2012, 07:56

I've just been through this and the technical answer is to look at your handbook to see the recommended engine RPM range at WOT. Mine was 5000-6000rpm.
The answer for me was to find a prop that would give about 5500 rpm at WOT.

This is something that you can take a guess at (regarding what pitch/no. of blades etc) but in the end you will need to put the prop on the engine and test the boat on the water with an RPM meter on it.

The non-technical option is to decide what is more important to you, top speed or acceleration and "hole shot" performance. If you want better acceleration you need the lower pitch but if you want to try for the best top speed the higher pitch prop will be the one to try.

Jason calleja · 20 September 2012, 12:45

The recommendations are 5500 to 6000rpm at wot. No i just want to buy a new ss propeller and don’t won’t do get the wrong pitch as here in Malta i will not find a shop that can give me a propeller to try it as they have no stoke they will bring it by order. I have a friend that replaced the aluminium prop to a ss prop with the same pitch and the engine began over rev with it. All i want you to tell me your opinion regard if i will buy 3 or 4 blade and what will be the correct pitch to keep my hole performance. Thanks Jason

Downhilldai · 20 September 2012, 13:06

The stated max RPM for the Merc F60Efi is 5950rpm. The rev limiter cuts in at 6100rpm.
A 4-blade prop, such as the Trophy, will give you better holeshot & grip, eg in turns, but will drag a touch more than a 3-blader, so you may be ok to run a 14" pitch Trophy, if you're happy with the performance you get out of the 14" pitch aluminium prop currently fitted. A 3 blade Vengeance is a basic spec prop, which should perform similarly to an aluminium 3-blader.
What's your reason for wanting a stainless prop and have you tried an aluminium 15" pitch prop on there?

Jason calleja · 20 September 2012, 13:18

I want to replace the propeller as it is starting to have a little dent of corrosion near the nut. And buy a ss prop as it will not corrode again and it make nice too. That’s the only reason. If i will buy an aluminium one i will spent less for sure.

Downhilldai · 20 September 2012, 13:25

The difference in performance will be negligible on a 60hp outboard. If you're unlucky enough to strike the prop, then the lower unit is much more likely to get damaged with a stainless, rather than aluminium prop. This is particularly so with a 60hp motor, as the lower unit components are relatively small.

Jason calleja · 20 September 2012, 14:00

ok thanks for all your info. i will try a 15pitch aluminium. thanks again

npm108 · 07 October 2012, 18:31

The Blackmax 15 will drop you down by around 200rpm to 5800, which is your ideal WOT RPM for that engine (WOT 5,500 - 6000rpm) always making sure to prop your WOT at typical load.

The reason your friend may have over-revved when changing to an S/S prop is because sometimes the diameter on an S/S prop compared to Alu of the same pitch tends to drop as well. Not always but I have found this on some props.

Diameter and blade size/shape make a huge difference as they are responsible for carrying the weight of the boat/load. The smaller diameter prop and prob smaller blades of the S/S will cause the prop to spin up quicker resulting in the over-rev at the same pitch.

I believe the Trophy Sport 15 would probably have you running at 5,700 given that one tends to reduce 100rpm or so when going from 3 blade to 4 blade, and change in pitch of 1 inch is around 200rpm (all theoretical).

Or did you already buy a Blackmax 15P?

Jason calleja · 07 October 2012, 20:09

No i have not bought the black max now as now we are out of season and i was still confused what to do but now i think i will have a try with the trophy after all you wrote. But i will buy it for the next season as now i have garage it .thanks for your help