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View Full Version : Q's on PROP for 50hp Mercury



thejumbie
06-01-2011, 09:09 AM
Hey guys,

i have a 1996 4.5m Quintrex Bermuda with 96 50hp Mercury (3 cyl 2 carb)

its a good little rig and easy to use,

i want it to go faster (considering my 20ft did over 40knots) as its painfully slow
i know a small ally wont go as hard as a glass boat but a bit faster would be good

It does about 36km/h at 4000RPM and 40km/h flat stick at 4500rpm
what prop do you guys recommend but without losing reasonable fuel economy?
this should be able to run to about 5200rpm max right?

prop at the moment is stock, part number - 48 73136 A40 13P
its an alloy prop and want to stay with alloy as a stainless might destroy box if i hit something...

cheers in advance

STUIE63
06-01-2011, 09:25 AM
where are you getting your speeds from a gauge or a gps

thejumbie
06-01-2011, 09:27 AM
its my GPS as i have a 60MPH speedo so needle only just moves lol

who want to swap my 60mph for a 35mph quicksilver guage

Owen
06-01-2011, 09:29 AM
I have a 4.55 Quintrex Escape with a 50hp 3cyl 3 carb.
Pretty sure the hull would be much the same as it's about same age.
Flat chat with just me in is 27kn (About 50 k's I think)
It'll pull 5200 rpm, but I really get little or no extra speed over 4500.
I think I have a 10.5x13P on it, but I'm away from home at the moment.
I do find that if I have a couple of guys in the boat that it's a struggle getting out of the water.
Not good in a following sea if you need to jump up on a wave.
I think if you go for the top end you're going to get the same issue.
I'm thinking of trading some top speed to get some more out of the hole power.

thejumbie
06-01-2011, 09:32 AM
cheers Owen, i know its not "slow" for an ally but i have so many toys that need towing..
also those speeds are with 3x70 kg guys plus and esky plus an extra 20l fuel so it might not be too bad as it does take off ok

STUIE63
06-01-2011, 09:38 AM
is your cav plate just skimming the top of the water when on the plane

thejumbie
06-01-2011, 09:45 AM
is your cav plate just skimming the top of the water when on the plane

im not sure, looks like im going fishing to find out

STUIE63
06-01-2011, 09:50 AM
it just seems strange your prop sounds about the right size and should rev out higher than it does

thejumbie
06-01-2011, 10:06 AM
im sure its the standard prop as i got 2 the same from old mate,
i bought the boat a few months ago and got it serviced straight away but yeah could be tuning.... economy seems good (i just sold my 150 V6 yammy lol) so maybe needs more juice through it

Toddy_again
06-01-2011, 10:25 AM
I think the max revs for these motors are between 5000-5500 rpm?

You should be looking at getting it within that range.Speak to somebody about tweaking your prop or getting another.

Toddy