Hi dodgetboy; Welcome to the world of Uniflites. I also have a 27 uni 1972 with
a pair of 318's, direct drive {1:1}
velvet drives, 1-1/4" shafts turning 14" x 10" cupped 3 blades. It originally
came with 14"x11" props. It will plane at 13 mph @ 2200 rpm, but not an
efficient speed to run. Normal cruising speed is 18-20 mph @ 2600-2700 rpm. WOT
is 32 mph @ 4000 rpm. Measured with sumlog and GPS and digital tacks. The boat
has the long cabin. hard top with bridge and duel controls.
These hulls are 27'-3" long with a 9'-7" beam. They are very strongly built yet
quite flexible and with a hard gel coat {which will shine up well } they tend
to get many flex cracks. Your single 360 sounds great. I would think you have a
reduction gear of 1.5:1 or more. As I understand, you should turn as big a
diameter prop as you can in the space, but allow 15% {per Michigan Wheel }
of the diameter for clearance from blade tip to hull. Then adjust the pitch for
a WOT of 4000 rpm. I would really load that engine up, because the 360 has
almost twice the low end torque as a 318. Take the prop to a good Prop-Shop and
tell them of your 5100 WOT, your gear ratio and what WOT you want, and they
should be able to re pitch it. Good luck! Ray
]
--- [email protected] wrote:
From: dodgetkboy78 <[email protected]>
To: UnifliteWorld <[email protected]>
Subject: [UnifliteWorld] Prop pitch, GPH, cruising speed, RPM
Date: Thu, 10 Sep 2009 23:01:54 -0700 (PDT)
I have recently bought a 1970 hardtop express. It is registered as a
28', 9'8" beam boat, from what I can tell, it is a 27'3" boat.
But thats not the question.
It came with a 225hp 318, and recently has had an update to a 360. The
transmission, prop, ect, was all left alone.
Top speed, if you got the guts to rev it that high, is around 24kts,
at 5100rpm. Yeah, ouch.
To stay on step, it takes 3300rpm, at about 13kts.
I have been cruising at 7-8kts, at 1800-2000rpm. Throttle is barley
open, and it burns around 4GPH at this speed.
Here is my question.
Does that sound right? It takes the 4bbls open a bit to keep it at
13kts. I just cant bring myself to run it that hard, for long periods
of time.
Could I pitch the prop to make it cruise better at 12-13kts? Or would
it just take more throttle at less RPM?
Either way, the 360 almost seems to big/too little.
I can be happy with it at 7-8kts, but was wondering if it was, well,
normal.
Other than that, this is the nicest handling, roomy, well built,
smooth riding boat I coould ever imagine, takes 4' following chop like
a champ, turns on a dime, and has a real "Heavy" safe feeling in the
water. My plans are to put a 330hp cummins in it eventually, that
should push it 15kts, and burn the same as the 360 at 8 I bet, but for
right now, I want to get the most out of my 360.
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