Right prop?

[Channel Ribs]

What would you put on a fairly light 6m RIB with a 135HP V6 two-stroke?

[outboardtech]

19 or 21 I would start off with . probably a 21 as you dont want to over rev that outboard . is that a merc or mariner ?

[Channel Ribs]

Originally Posted by outboardtech

19 or 21 I would start off with . probably a 21 as you dont want to over rev that outboard . is that a merc or mariner ?

Mariner.

'Tis a nice engine.

[Downhilldai]

135 Opti?
This has a 2.00:1 gear ratio, so on a lightweight 6m RIB, I'd also say 21" pitch, but it may need something coarser. What RIB is it?

[Robbie Diesel]

A Friend of mine had a 6 Metre Humber Destroyer with a new 150 Optimax which we did a fair bit of prop testing on and the 21" Laser 2 was probably the best all rounder. So I would probaby say the 19" Laser 2 on a 135hp? Go to Ebay United States amd you'll pick one up for buttons

[outboardtech]

DEFINETLY a 19 or 21 . you have to remember here that the LOWER THE PITCH YOU GO THE MORE REVS you going to get from your outbard but will loose TOP END SPEED . The higher the pitch you go the LESS REVS you will get but will have the TOP END . depends what you want it for . If you pulling kids on ringo etc etc then you need that acceleration out the HOLE and the 17 will perform . Both will work

[Downhilldai]

Originally Posted by Robbie Diesel

A Friend of mine had a 6 Metre Humber Destroyer with a new 150 Optimax which we did a fair bit of prop testing on and the 21" Laser 2 was probably the best all rounder...

I wouldn't disagree with that

Originally Posted by Robbie Diesel

.... So I would probaby say the 19" Laser 2 on a 135hp?

If it's a 135 Opti, then I would disagree, as the 150 Opti has a 1.87:1 gear ratio and the 135 Opti has 2.00:1.
This lower gear ratio on the 135 would suggest that the same pitch prop would be needed as the 150, on an equivalent size boat, not a finer pitch.

All this, of course, would be irrelevant, if the gear ratio isn't 2.00:1.

Malthouse: What RIB & motor are we talking about here?

[Channel Ribs]

Originally Posted by Downhilldai

Malthouse: What RIB & motor are we talking about here?

The RIB is of unknown heritage, but I will get a photo for ID. I suspect the hull shape will be easily recognised.

The motor is not the Opti, it is the other V6 135HP.

I also have a sneaky fear that at some point it has had the nuts revved off it.

[Robbie Diesel]

Originally Posted by Downhilldai

I wouldn't disagree with that



If it's a 135 Opti, then I would disagree, as the 150 Opti has a 1.87:1 gear ratio and the 135 Opti has 2.00:1.
This lower gear ratio on the 135 would suggest that the same pitch prop would be needed as the 150, on an equivalent size boat, not a finer pitch.

All this, of course, would be irrelevant, if the gear ratio isn't 2.00:1.

Malthouse: What RIB & motor are we talking about here?

Oh right, Sorry, I had no idea they were different gear ratios between the 135/150. You live and learn. I'm pretty sure the 150 opti we tested both the 19" & the 21" laser were both within the recommended rpm range. The 19" went to 5700ish rpm with better acceleration and the 21 was around 5300 rpm. Cruised better but not as punchy acceleration. Probably a 20" would have been ideal but wasnt available at the time. Best thing is to try and borrow one of each from a friend and test them back to back on the same day.