I’ll start by saying I’m not building a boat or anything, just purely interested in the topic and would like to chat and learn.

On an outboard powered CAT, what is the best centerline and why?

Narrower with the props slightly protruding into the tunnel or wider with the prop all the way out of the tunnel? How do you decide the measurements? Does a true tunnel or center pod bottom change this?

Did you ever find an answer to this? I am going to repower a 28ft profile cat with twin 400s or 450s and would like some info on where to mount them.

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I would get in touch with Shaun Torrente for advice and for purchase of motors


Shaun Torrente Racing
Shaun Torrente Racing Established As Authorized Mercury Racing Dealer


STR X-Act Laser height kit
https://shauntorrenteracing.com/coll...t-kit-sm-bravo





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Interested to see some of the answers on this question .

When I started this post I had zero experience with twin cats in general rigging, setup, and driving. I’m still no expert, but I have a little more experience now.

I’m not sure how much data we will get on this topic. It’s one of those things that is kept quiet and everyone has their own preferences and every boat reacts different with everything setup related.

With the combination of my existing experience in the V bottom world at Laveycraft when I started this post, along with new experience rigging/setup/testing/etc on a few different cat brands twin IO and OB (Victory, Skater, RPM, Eliminator).

A very general rule of thumb; blade in the tunnel will aid in bow lift, no blade in tunnel will not. Then things change with prop rotation in/out, rake, diameter, and much more. It’s a fine line that each boat reacts different to and requires testing different centerlines, matched with the correct prop, overall CG of the boat, etc.

Theres no written rule or one size fits all.

The Norwegian Hydrolift racing cats had the engines in the center of the tunnel, like on a single-engine cat. That was the fastest.

It was of course very hard on gear cases and mid sections.

Look at the first boat here:

https://www.cormate.co.uk/heritage.html