Optimax 115 Propeller size?

whackywoody · 23 June 2013, 08:58

Morning, looking to get my boat out on the water for the first time this week (if the weather behaves) but need to purchase a prop as the one I got with the engine is kn$%kered! I have never put this boat in the water before so have no starting point and have also tried the mercury propeller selector which was advising me to get a 12" pitch which I believe is to small as I was thinking about a 19" pitch. My specs and usage are as follows:

Engine: Year 2000 optimax, V6 115Hp
Boat: 6m humber destroyer
Total Weight: 900 - 1000kgs
Usage: Mid range cruising and top speed

Has anybody got any recommendations for pitch and diameter size I should go for that would suit the above requirements?

Thanks

Pikey Dave · 23 June 2013, 09:47

19" sounds a bit high, I'd have thought 15-17" depending on your loadings. You don't want to be overpropped. I'd try & borrow a 17" stainless & work from there.

macattack101 · 23 June 2013, 17:43

I've got a 6.2m with 115hp and my prop is 13.25 diameter with 17 " pitch. Works well for me giving 33 knots with a family and kitchen sink loaded and just bought a new spare aluminium for about £100.

nugent · 23 June 2013, 17:49

Quote:

Originally Posted by whackywoody

Morning, looking to get my boat out on the water for the first time this week (if the weather behaves) but need to purchase a prop as the one I got with the engine is kn$%kered! I have never put this boat in the water before so have no starting point and have also tried the mercury propeller selector which was advising me to get a 12" pitch which I believe is to small as I was thinking about a 19" pitch. My specs and usage are as follows:

Engine: Year 2000 optimax, V6 115Hp
Boat: 6m humber destroyer
Total Weight: 900 - 1000kgs
Usage: Mid range cruising and top speed

Has anybody got any recommendations for pitch and diameter size I should go for that would suit the above requirements?

Thanks

Engine: Year 2000 optimax, V6 115Hp. In line 3 isn't it? Or is it not a 115hp?

whackywoody · 23 June 2013, 17:59

Quote:

Originally Posted by nugent

Engine: Year 2000 optimax, V6 115Hp. In line 3 isn't it? Or is it not a 115hp?

Its an early one and not sure they were that common. Its a 2.5L V6 (got 6 spark plugs as I have been through the expense of changing them all

) and is definitely 115Hp (wish it had more horses)

Pikey Dave · 23 June 2013, 20:20

Quote:

Originally Posted by whackywoody

Its an early one and not sure they were that common. Its a 2.5L V6 (got 6 spark plugs as I have been through the expense of changing them all

) and is definitely 115Hp (wish it had more horses)

That's a big block for just 115hp, are you 100% sure?

nugent · 23 June 2013, 20:23

Quote:

Originally Posted by Pikey Dave

That's a big block for just 115hp, are you 100% sure?

Yep me thinks its a 135 sir with different hood

ashbypower · 23 June 2013, 20:51

V6 115 !! well our 125 is a 3 pot !!! I'm with nugent on the numbers !!

willk · 23 June 2013, 20:58

It's not often you ask for prop advice and get a bigger engine. Score!

Of course, your insurance is shot...

mickab9 · 23 June 2013, 21:02

Hi, I have one of these (115) on a 6m destroyer. Definitely 3 cylinders..... I'm running a 17 pitch after much chopping and changing! Works extremely well (35kts ish) with 4 divers and kit at about 5000rpm.

whackywoody · 23 June 2013, 21:04

Quote:

Originally Posted by nugent

Yep me thinks its a 135 sir with different hood

I wish that was the case but I have put the serial number into the mercury marine parts catalogue and this is what I get:

Parts catalogue number 803502 00 - 115/135/150 DFI (2.5L)

Service Literature for MERCURY DFI OPTIMAX DIGITAL 115DFI L DIG

Its a year 2000

Who knows maybe that is my next project to get the block bored out to 150Hp - More power

Any suggestions on prop sizes please

whackywoody · 23 June 2013, 21:11

Quote:

Originally Posted by mickab9

Hi, I have one of these (115) on a 6m destroyer. Definitely 3 cylinders..... I'm running a 17 pitch after much chopping and changing! Works extremely well (35kts ish) with 4 divers and kit at about 5000rpm.

No its definitely got 6 x cylinders as I have changed the plugs, the newer ones have 3 cylinders. What diameter prop is your 17" pitch and is it alloy or stainless steel! Please don't be offended but I would be disappointed with 35 knots I will have to sell the boat and start a new project

unless nugent is right and I have a 135Hp with a 115 Hp hood

willk · 23 June 2013, 21:22

Quote:

Originally Posted by whackywoody

Please don't be offended but I would be disappointed with 35 knots I will have to sell the boat and start a new project

Well, 35kts on a 6m RIB with 115hp sounds about right to me.

mickab9 · 23 June 2013, 21:27

My prop is stainless steel, 13.5 x 17". Pretty sure it has "vengeance" stamped on the side if that helps. Very happy with 35 kts on a 115 with approx 600kgs of divers and kit! I'm sure you would achieve more with a lighter payload mind but its a good all round pitch for me. Can't afford to smash up my divers too much :-)

mickab9 · 23 June 2013, 21:28

PS you're probably right about the year. My engine is an Optimax approx 2005.

whackywoody · 23 June 2013, 21:37

Quote:

Originally Posted by mickab9

My prop is stainless steel, 13.5 x 17". Pretty sure it has "vengeance" stamped on the side if that helps. Very happy with 35 kts on a 115 with approx 600kgs of divers and kit! I'm sure you would achieve more with a lighter payload mind but its a good all round pitch for me. Can't afford to smash up my divers too much :-)

Ah, forgot you mentioned divers (4 x divers 600kg that's a lot of pie eating

). However you are only revving to 5000 rpm as I thought max revs was 5800, do you think I could max it to a 19" pitch prop or will that overprop it?

I'm determined to be the fastest man on the mersey

Turbodiesel · 23 June 2013, 21:38

Yes its a V6 the early 115 opti's were V6. Not many of them about.

whackywoody · 23 June 2013, 21:55

Quote:

Originally Posted by Turbodiesel

Yes its a V6 the early 115 opti's were V6. Not many of them about.

Thanks Rob, going slightly off topic myself here but what would it take to bore out the block to 150 or even 175hp. Obviously I would av to get new pistons and rings but what about the fuel rail and ECU would they need to be changed and anything else?

Pikey Dave · 23 June 2013, 22:02

Quote:

Originally Posted by whackywoody

I'm determined to be the fastest man on the mersey

You need to prepare yerself for some disappointment then

mickab9 · 23 June 2013, 22:38

Quote:

Originally Posted by whackywoody

Ah, forgot you mentioned divers (4 x divers 600kg that's a lot of pie eating

). However you are only revving to 5000 rpm as I thought max revs was 5800, do you think I could max it to a 19" pitch prop or will that overprop it?

I'm determined to be the fastest man on the mersey

Mmm wouldn't want to guess your all up weight versus revs. Suspect 19" might be a big bite and could lose you some hole shot and options in bigger seas. Someone else on here might have tried it though......