Rocky Mountain Monte Carlo

Designs for inboard or outboard power

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tysman52
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Joined: Thu Oct 18, 2012 1:17 pm
Location: Salt Lake City, Utah

Re: Rocky Mountain Monte Carlo

Postby tysman52 » Tue Oct 17, 2017 2:06 pm

Can I get some engine and transmission advice? These are dumb questions but I don't want to screw up this engine purchase LOL. I am not an engine guy and I'm going out on a limb here ! I decided to go with the PCM 6.0 L. My rudder is placed about an inch to the port side. I have a star board Helm. Do I need a left or right Prop spin? I talked to Richard at discount inboard. The 1:1 transmission gives a left. The 1:23 is reverse and also has a down angle of @ 9 degrees which lets it sit more level. I don't think I necessarily need to do the angle transmission for my size standpoint but can't hurt?

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Bill Edmundson
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Re: Rocky Mountain Monte Carlo

Postby Bill Edmundson » Tue Oct 17, 2017 3:36 pm

As I remember, for a starboard helm you use a right hand prop rotation (clockwise looking from the rear). Gear wise, if you use a 1:1 then if it was 12" pitch, you will get the same results with 1.23:1 and a 15" pitch. If the 1.23 is a ZF63a, it can be set-up left or right.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

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jenko
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Re: Rocky Mountain Monte Carlo

Postby jenko » Tue Oct 17, 2017 4:18 pm

What I found with the 12''props was they start to loose performance around the 4000 rpm shaft speed (their slip decreases from 0 srpm to around 3000 srpm stays the same to around 4000 srpm and then slip starts to rapidly increase (I tested with 4 different gear ratios so hull speed is not a factor with these findings))so if the max rated rpm of the pcm is 5000rpm or better I would go with 1:1.23ratio which would allow you to use a 12'' to 14'' prop efficiently
Last edited by jenko on Wed Oct 18, 2017 2:53 pm, edited 1 time in total.

tysman52
Posts: 36
Joined: Thu Oct 18, 2012 1:17 pm
Location: Salt Lake City, Utah

Re: Rocky Mountain Monte Carlo

Postby tysman52 » Wed Oct 18, 2017 12:24 pm

So I will plan on ordering the 1.23:1 right hand spin. Thx! JT

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Bill Edmundson
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Location: Birmingham, AL, USA
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Re: Rocky Mountain Monte Carlo

Postby Bill Edmundson » Wed Oct 18, 2017 2:06 pm

JT

I think the 4000 srpm is about blade tip cavitation. The larger the prop the lower the srpm. A 14 inch prop should be affected at 12/14 x 4000 srmp. These are just rough numbers.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build


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