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Old 01 March 2016, 16:38   #1
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Country: UK - Scotland
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Boat name: Ron Mor
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Prop options for Mariner 125hp

Hi All,

I have purchased a Delta 5.8m Rib with a 125hp Mariner 2 stroke.

It has a Mercury Marine Lazer II - 48.16990 20P on it at the moment.

The prop is OK but was thinking of getting a 2nd/spare.

Is there a better prop to try for this boat engine?

Cheers Stevie
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Old 02 March 2016, 03:22   #2
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Country: UK - Wales
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Engine: 150hp outboard
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We have only ever had good experiences with a High 5 prop, we have had a High 5 for over 20 years and it has been used on outboards & stern drive boats with great results, we also have a Laser 2 prop and others that get little use
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Old 02 March 2016, 12:24   #3
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Country: UK - England
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RIBase
How is it running with the current prop?
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Old 02 March 2016, 12:58   #4
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Is it within the engine's specified WOT rev range under your normal usage with the current prop?
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Old 02 March 2016, 14:29   #5
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Country: UK - Scotland
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Hi all, appreciate the replies

Whiskylee - aren't the High Five props for 135 hp and above? Would they work well on the 124 hp I have? Are the Laser 2 props surplus? PM if they are compatible and available.

Searider/Paintman - had it out as soon as I got home (as you do). WOT it reached 5000 rpm and 45 knots (ish with some more in there if I'd feathered it better). At 3500 rpm it was 26.5 knots and 2000 rpm 8 knots. Tick over at 800 rpm gave 2.5 knots. Does that sound right?

I've no idea what the engine's specified WOT rev range is. Will dig around for that info, unless anyone out there can help with that?

There is a brutal pick up between 2000 and 3500 rpm. I've ordered Hydrifoil fins to see if I can smooth that out a bit, they did well on my previous rib with a 90hp Mariner.

S
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Old 02 March 2016, 14:49   #6
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Country: UK - Wales
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The even no's are for 75 - 115hp (20,22pitch)

I keep all our props, wouldn't want to sell any, they look too good on the garage wall !
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Old 02 March 2016, 19:04   #7
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If your motor is the 125hp here: Mariner 125 - Mercury Marine then the WOT should be 4750-5250.
At 5000 you're right in the middle of the range which suggests with the loading you had that the prop is fine - although you seem to be saying that you could have gone faster so your actual WOT revs might be higher.
Be worth another run with what you would normally have in the boat to see if it stays in the range.
There are various prop calculators on the internet & I'd be inclined to enter your details into a few to see what comes up.
I've just had a play with this one & for 'good all round performance' it comes up with 3 props of 20 or 21 pitch - including what you've got fitted.
https://www.mercurymarine.com/en-gb/...tion#/step-one

ETA you mention 'brutal pick-up'. If that is your engine then the spec listed says that up to 1800 rpm (ish) it only runs on two cylinders so the other two coming in could explain it.
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Old 05 March 2016, 03:12   #8
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Cheers guys,

I did not know about the 2 cylinder thing at low revs!

So from this I'm hearing that the Laser II 20P prop is fine for this setup and getting a similar one as a spare would be sensible.

Anyone out there have one to sell?

Any advice on where I should go to get one?

S
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Old 05 March 2016, 05:17   #9
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Put a wanted add on here

Internet auction sites etc etc
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Old 05 March 2016, 06:55   #10
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Country: UK - Scotland
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Done! Ad in bits and pieces.

Not much on ebay, all from the states.


S
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