Prop for 4.74 V-Sea with 60hp 4 banger

[fishingrod]

Trying to help a mate who just purchased a 4.74m Seafarer V-Sea (Mk1) that’s fitted with a 2011 60hp Mercury Big Foot 4stroke. Big Foot being the larger gear box with 2.33 ratio.
The current prop (fitted by previous owner) is way too small and the boat is painfully slow. It’s an Mercury SpitFire alloy 4 blade 13.8 x 11 pitch.
From what I can see 13-14” pitch seems more appropriate.

With 2 persons, 40 Litres of fuel, basic safety, but no fishing gear his approximate GPS speeds are :
10 knots @ 4000
11 knots @ 4200
12.5 knots @ 4400
13.3 knots @ 4600
14.0 knots @ 4700
14.5 knots @ 4800
15.5 knots @ 5000
19.5 knots @ 5600
WOT is >5800 with the current prop, but we won’t sure on the max rated engine RPM so didn’t try any harder.

No "foil" is fitted. Whist on the plane the anti-ventilation plate has a “film” of water passing over it, but I would not call it submerged.

Understand that people like SOLAS can provide advice, but hoping to get some recommendations from the Ausfish community on prop size/types/models to consider. With some luck he can find something second hand on Gumtree etc.

I’m hoping we can get him a 17-22 knot cruise in the region of 4000-4600. Achievable ?

[Noelm]

If he's only getting 19 knots at 5,600RPM, I think it would be a bit optimistic to expect to get around 20knots at 4,000! do you know if 5,800 was flat out? if it was, then sadly it's probably close to the right prop now, 60 HP for that boat is pretty well minimum power, most had 70 on them, and only a handful of them had 55HP 2 strokes when new.

[Dignity]

Trying to help a mate who just purchased a 4.74m Seafarer V-Sea (Mk1) that’s fitted with a 2011 60hp Mercury Big Foot 4stroke. Big Foot being the larger gear box with 2.33 ratio.
The current prop (fitted by previous owner) is way too small and the boat is painfully slow. It’s an Mercury SpitFire alloy 4 blade 13.8 x 11 pitch.
From what I can see 13-14” pitch seems more appropriate.

With 2 persons, 40 Litres of fuel, basic safety, but no fishing gear his approximate GPS speeds are :
10 knots @ 4000
11 knots @ 4200
12.5 knots @ 4400
13.3 knots @ 4600
14.0 knots @ 4700
14.5 knots @ 4800
15.5 knots @ 5000
19.5 knots @ 5600
WOT is >5800 with the current prop, but we won’t sure on the max rated engine RPM so didn’t try any harder.

No "foil" is fitted. Whist on the plane the anti-ventilation plate has a “film” of water passing over it, but I would not call it submerged.

Understand that people like SOLAS can provide advice, but hoping to get some recommendations from the Ausfish community on prop size/types/models to consider. With some luck he can find something second hand on Gumtree etc.

I’m hoping we can get him a 17-22 knot cruise in the region of 4000-4600. Achievable ?
Can you confirm that prop size as the pitch seems to be way too small given a diameter of 13.8, the blade would have to be virtually vertical from the hub.

[fishingrod]

Thanks Guys,

Noelm - there is more than 5800 in it. We should pushed it harder, being EFI I assume there is a automatic rev limiter. When throttle is applied it responds and accelerates quickly at all speeds, even top end, which I’m guessing means the donk has the power to spin a bigger pitch ?

Dignity - 13.8x11P is correct according to a receipt the previous owner provided (PN 8M8026560) and a few websites : https://www.boatpropellerwarehouse.com/product/28776/spitfire-pontoon-13-8-x-11-mercury-rh-propeller-48-8m8026560

Looks like that size optimized for Pontoon boats, presumably low speed planing.

Looking at online reviews which I realize may be slightly exaggerated suggest a 60hp Merc BF can push a 5.3 Stacer CC to 27knots (14” pitch) and a 60hp High Thrust Yammy pushes a 4.85 Streaker to 30knots (11 1/8dia x 13” pitch)

[Noelm]

OK, if the motor still has more RPM in it, then you might be in luck, only option is guess work or borrow a prop, or get someone like Solas to come out and try props for you.

[Dignity]

Definitely change the prop, that's a fairly flat blade at that pitch.

[BigE]

have the below prop sitting in my shed if you want give it a run, it in as new condition.

had it on a 60HP merc command thrust pushing a 5950 long boat and it gave excellent fuel economy and speed.

PM me if you want to discuss.

it's a 14 x 13 four blade SS

BigE

[BigE]

PS the yammie big foot and Merc command thrust are the same gear box.

BigE

[fishingrod]

have the below prop sitting in my shed if you want give it a run, it in as new condition.

BigE - thanks for the offer mate, but testing might be a bit difficult as I’m Sydney based.

Yours does look like a reasonably good match.

[Fed]

Might help.

[fishingrod]

Good table Fed, some interesting figures there. Suspect it’s for 2 strokes as it shows WOT RPM as 5000-5500. The fourstroke is labeled as WOT being 5500-6000 rpm

[Fed]

Try this one.

[rodneyk]

Bigfoot gearboxes were designed for barges and Houseboats so at 19 knots thats pretty fast for a barge but not a 4-7 Mtr Boat .
Small HP engines dont have the cubes to push big propellors . Smaller gearbox = Less drag also more props to choose from

[fishingrod]

Fed - thanks for the second table. It looks closer to the mark. I’m no expert, but their recommend pitches seem slightly larger than I expected.



also more props to choose from
Agree - there is very little around second hand.

Thanks for everyone’s replies. A new prop has been ordered from SOLAS. Will post an update in a couple of weeks after water trials.

[BigE]

Hi Fishingrod

what size did you end up ordering ? did you go 3 blade or 4 blade.

BigE

[fishingrod]

Hi BigE
Solas didn’t seem keen on a 4 blade. They seem to only offer 4 blades on larger engines (>90hp).

It’s my mates first boat so he didn’t want to spend too much. Have ordered a 3 blade alloy, 13.8 Dia x 14P. Admittedly Solas was recommending a 13P, but on our request, allowing us to try a 14P.

We’ll have to see how it goes,
Cheers, Rod

[rickmarlin62]

I own a vsea had a 60yammie 2st on it ran a 13 1/4 x 17p revved out fine did 29knots upgraded to 90yammie now I think 14 will still be underpitched......I have 13 1/4 x 15 pitch stainless with removable hub for sale 200 bucks im at lake macquarie

[fishingrod]

RickM - thanks for the SS offer but have already purchased and started testing with SOLAS alloy.

The engine is the 4stroke 60hp Bigfoot model, which has a 2.3 gear ratio and spins 13.7-14inch diameter props. Standard models have a gear ratio around 1.8. This makes it difficult to compare.

My mate tired the 14P SOLAS and only achieved 5100 WOT maxing out at 22.5 knots GPS.
We thought about raising his engine a little, but didn’t think it would gain us an extra 500rpm.

He has now exchanged for a 13P and it easily achieves 6000 WOT at 22.7 knots GPS.
I’m suprised there is such a big WOT rpm difference. It’s all black magic !

Other figures with the 13P are :
4500 - 16.1 knots (GPS)
5000 - 18.9 knots
5500 - 20.7 knots
Looks like my mate is going to stick with the 13P for now. Understand that a Stainless would generally give slightly better performance. SOLAS actually has more blade options available in Stainless.

[Moonlighter]

Its not impossible to pick up several hundred rpm, even 400, if the engine is currently set way too deep and is then lifted to the correct height.

The accepted wisdom is to first get the engine height set right, then swap props if still necessary.

If it is done the other way (prop first) you can still end up well under the optimum performance. And if you then lift the engine height to where it should be, then the prop is probably wrong all over again.....

Lifting a 60hp is quick easy using the boat trailer method. And its free if you do it yourself.