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Reversing a reverse rotation boat

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tleed View Drop Down
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    Posted: January-15-2021 at 6:04pm
I'm starting a new thread about reversing the rotation of an engine in a boat that was initially reverse rotation from the factory. It could be mercifully short, or painfully long. I'm going to suggest that we keep out of this thread discussion about boats with dual engines, mostly because one of those engines is reversed for reasons that don't interest me.

What I am interested in is why CC and other ski boat manufacturers back in the day routinely reversed engines in inboard ski boats. Apparently nowadays that isn't done.

From reading on this site years ago, I gleaned that one main reason is that the torque and thrust of a revving engine lift a boat on the right front side. Because every piloted boat has a driver, that thrust counters the weight of the driver. In a standard rotation setup, the weight of the driver adds to the torque of the engine, burying one side of the boat deeper in the water, as opposed to leveling it out.

Our boats run 1600-2500 lbs. I read about a big, porky ski boat the other day that was way over 4000 lbs. Whew! Yes, it has a much more powerful engine. But it also has a lot more mass to resist the engine's kick. So, (although I might be reigniting an old thread that's been beat to death), I wonder if that's the main reason why our ski boats had reverse rotation? The mass was less, and the torque of the engine produced a greater effect? Is that effect more exaggerated in a boat with significantly less mass, like a vintage CC? Will that reach objectionable levels if you add horsepower?

My questions are oriented toward putting an 18" 1968 Wildcat back together with a 440. That's a not very huge ski boat with a pretty aggressive power package, compared to today's rigs. Would it be a terrible idea to "reverse" this particular engine to standard rotation?

The other main topic I'd like to see addressed here is whether you can *easily* convert the boat to standard rotation. I've read enough to know there's lots of info here about the engine itself. It's not hard to reverse an engine if it's out of the boat. Cam, dizzy firing order, etc. What I'd really like to know is other more esoteric info, such as whether the prop and rudder are/were offset from each other to finesse the handling characteristics?

And, yes, I realize there's the obvious: the prop has to be changed. But do you have to also change anything else?


Thomas



1974 Southwind 18 with 318 cubic inches of reverse rotation roller cam "Moparvation"
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8122pbrainard View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: January-15-2021 at 6:40pm
Originally posted by tleed tleed wrote:

But do you have to also change anything else?

Most transmissions need to be indexed for the rotation. 


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67 ski nat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67 ski nat Quote  Post ReplyReply Direct Link To This Post Posted: January-15-2021 at 8:17pm
There is a very excellent machine shop engine builder in my town that could easily pull that off for a fee $$$$$
Time, money, skill

Have you tried to find parts yet crank, cam for the 440
What about alternator, starter, h20 pump rotation
Oh new carburetor the old one will blow air out, not suck in

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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: January-16-2021 at 6:39am
Since now you're thinking about making the engine a normal rotation engine, probably the biggest things to worry about that haven't been mentioned are the crankshaft wick/helix lines on your reverse rotation 440. and whether the pistons and rods are flopped around for reverse rotation.

You'll have a rear main seal leak if you turn a reverse rotation crank in the normal direction and there are different opinions on piston orientation.

You already know you'd need a new cam and oil pump intermediate shaft with the right gear on it and a new starter 

Your distributor in the picture of the engine when you bought it is an automotive one, so replacement is up to you. It would work for normal rotation without the collar but there's that safety thing to worry about

The alternator won't care which way it's turning  and the engine circulating water pump might be directional and pump a lot better in one direction

Now as far as needing that new carburetor that 67 Ski Nat mentions, only he may know what he's thinking.........maybe Wink

Originally posted by 67 ski nat 67 ski nat wrote:


Oh new carburetor the old one will blow air out, not suck in
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: January-16-2021 at 6:51am
It looks like nobody wants to talk about reverse rotation vs normal rotation reasons but how the boat rides will depend a lot on whether you're the Lone Ranger out in the boat or if you take Tonto and some friends along for a ride Wink

It's been discussed plenty of times over the years, with no perfect answer.

If you crawl under the boat, you'll see if there's any offset between the prop shaft and the rudder
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: January-16-2021 at 8:00am
I have owned and driven several cc’s that have been repowered with LH engines/props. The smaller the boat, the bigger the effect. None of them drove as well as their RH counterparts. The smaller one was borderline dangerous due to the excessive starboard lean. You really had to be careful about stuffing the nose and had to plan turns very cautiously, especially in varying water conditions and at higher speeds.

The 18’ wildcat is a bit bigger, which would concern me less... but despite its size, its running surface is still pretty narrow. I sure wouldn’t do it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tleed Quote  Post ReplyReply Direct Link To This Post Posted: January-16-2021 at 10:02am
I think I asked a broader question than the answer that I wanted. If I had to rephrase it, I'd say "What are the effects on handling of reversing a reverse rotation engine in a single-screw ski boat?"

I think I have the answer now, but if anybody has more info to add, they're still welcome to chime in.

I interpret the above as: you can do it, but the smaller and narrower the boat, the more detrimental the effect. I suppose I might add that any increase in horsepower would only exaggerate the effect.

I'll also add that I looked under my Wildcat and a couple other boats. I can't visually see an offset in the prop/rudder relationship, so if it's there, it's minimal. That's why I asked. My eye doesn't tell me definitively whether there is one or not.
Thomas



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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: January-16-2021 at 10:38am
Cc didn’t offset the rudder like some other manufacturers do.

I would not say that the increased hp exaggerates the effect... the effect of a LH prop would be consistent on any given hull. Combine that detrimental effect with increased hp through, and the danger certainly increases. More so than the same additional hp on a RH prop boat imho.

Easiest way to decrease the enjoyment and desirability of a classic Cc, I’d say.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67 ski nat Quote  Post ReplyReply Direct Link To This Post Posted: January-16-2021 at 10:59am
Interesting topic to understand CC design, but a ‘heavy lift’ to pull off reversing motor
Flop steering and controls to others side??

The carb comment was a funny, my emoji not working (winking smile emoji here)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: January-16-2021 at 12:48pm
If you could put in a gear reduction transmission, you can run righty/lefty (prop/engine respectively).  If.....

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tleed Quote  Post ReplyReply Direct Link To This Post Posted: January-16-2021 at 1:31pm
Thank goodness you clarified that carb funny, because I was trying to figure out how to hook the bilge blower to the bottom of my motor to get the air to go backwards.

I think I'm going to leave that alone now and go work on the gear reduction transmission idea…right after I finish swapping the controls to the other side, too. Back in five…
Thomas



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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: January-16-2021 at 1:42pm
Originally posted by tleed tleed wrote:

I think I'm going to leave that alone now and go work on the gear reduction transmission idea……

A 1:1 down angle trans would be a better choice over any reduction. Reductions typically swing larger diameter props and that would get you into hull/strut mods. A down angle would still reverse the rotation. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: January-16-2021 at 5:59pm
I think that if I had the engine you have, fresh from the PO, never run yet and being a Reverse Rotation engine, complete with the wrong distributor before I spent any big amount of money, I'd get it running (even if it's on a wooden cradle). with a carburetor and whatever distributor you can come up with that fits.

That way at least you'll know it runs or you may find some other "surprises"

Ya never know Wink
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