Did it drive differently after you cut the shaft?

Yours is a short hull like the Classic isn't it?

Bruce,

I remember getting under Charlie's 69 Cuda when we were trying out an Acme prop. I don't remember the exact distance but was surprised how far aft of the strut the prop was. I'd say the 2&3/4" Todd mentions would be very close to what I saw. 

Based on the 3 Classics I've driven, the older short hulls drive much differently than the long hulls, although both have larger than usual strut to prop distance.

No problem. I'm going over there for New Years and will make a point to get down to the boat house with a tape measure. 

8122pbrainard wrote: No problem. I'm going over there for New Years and will make a point to get down to the boat house with a tape measure.

Shouldnt be a problem.  COVID doesnt survive at -30* F

Well, through the magic of that thing called a search, here's a picture of Charlie's original shaft and Charlie too 

Since he got a new shaft when the old one bit the dust, there's probably not much need for Pete to measure Charlie's shaft again since it sounds like the new one was probably shorter anyways.

You can easily see the amount of shaft sticking out and get a  good idea of the length and the hull clearance since there's a ruler in the picture showing the clearance

Just trying to save Pete from having to probably lay on the ice with a flashlight on New Years Eve to get a picture of what isn't original and from the sounds of it the one in the picture may not be original anyways.(but I'll guess that it was the original) 

We're a step ahead of you Ken. Charlie is pulling the paper work on the new shaft  He's great on taking notes plus he and I both remember the new shaft was intentionally ordered 1" shorter than the original. He also still has the original shaft with the cutlass witness markes. Between notes, memory and the old shaft we should come up with a very good figure. 

As far as laying on the ice, that's a no since he has his aerator is running so we'll drop the canoe in the slip.. 

A video might be asking too much 

Our Cuda with the short shaft cavitates on left left hand corners and when riding over good size chop, something it did not do before the engine and shaft swap. I also do not think it corners as well.   I do not think the weight of the engine is an issue as the 318 poly was heavy due to all its beefy cast iron Chrysler parts and our Ford FE has aluminum oil pan, bell housing, intake and exhaust manifolds and may even be lighter than the Chrysler.   As far as it weird bow steer at medium speeds, that could be due to the combination of the wrong rudder port which needs to be recessed and the increase in prop size from 12x13 to 12x16.  However, it did not steer like that prior to the engine/shaft swap. We have the newer style rudder. Reid thinks it has something to do with the rudder port as the part of the port that is supposed to be recessed is mounted directly to the hull and is not recessed. .  For now, I want to get a longer shaft in it, maybe not as long as Correct Craft installed, but longer than what we have now. Initially, we were worried about running all that 427 power through an ARE shaft, but that is no longer a concern.  

Here's what's on Charlie's Cuda. The original shaft was 41".  Using the wistness marking on the old for a guide the distance between the prop and the strut was 2&1/2". The new shaft is a GP double taper and per the request, they made it 40". This gives 1&1/2" between the prop and hub. Charlie is running a 540 giving a prop to hull clearance of about 5/8".  

He says there are no different handling characteristics from the original. 

EDIT: Per the strut/shaft/rudder list, the shaft length is listed as 41" so, I'd say Charlie's original shaft was factory. 

It's been a long time since I've been in a Mustang bilge so I can't remember how close the log is to the trans. The Cuda log is real close to the point where tightening the nut on the end of a double taper shaft isn't easy. There's only about an inch between the trans and shaft coupling faces so there's no way a socket and ratchet will fit. The answer is making a special socket by cutting the length down and then welding a flat bar handle on it's end. 

+1 ^^

Some more of that same math 

Same strut, same mounting angle, same distance to the log from the strut

Relative to the transom or rudder...

What exactly are you looking for? From the start of the thread, it sounds like just a shaft length? 

Not enough...

That's what I thought. 

Tim,

I know he wants to go back to the original length. How is that an "errant path". The overhung load issue? 

In your experience what exactly happens without minimization? "reliability and performance perspective" is pretty vague. 

 

There are 2 things to consider, prop to strut clearance which affects shaft performance, and prop to hull clearance which affects boat performance.  I don't see how anyone can disagree that shaft performance is secondary to boat performance. If perfect shaft performance is causing poor boat performance, what good is the perfect shaft performance?

In the case of the Cuda, Correct Craft put long shafts on them for a reason. While some people might cringe at the sight of their excessive prop to strut distance, they perform well and have been running like this since the 1960's.  In our case, we went with a short shaft in order to have perfect shaft performance as we were installing an engine that had 300 hp, much more than what was in the boat originally, and we knew it would require more prop, which it did.  We went from 12x13 to 12x16.

I've explained the handling characteristics on page one.  Based on my experience with 2 Cudas, I believe lengthening the shaft will be an improvement and make the boat handle better as it did with the longer shaft.  I'd rather not go to 2.5", but certainly .5" is inferior as far as boat performance goes to the original spec of 2.5".

As far as weight of the engine, I cannot find an Interceptor spec that has the weight of the FE marine engine.  I did find automotive specs that have the 318 at 550# and the 427 at 650#.  Chrysler Marine states that the 318 was 750# with all their beefy marine parts on it.  Given all of the light aluminum parts that the Interceptor has, I'd bet the 2 marine engines weigh about the same and the Interceptor maybe slightly lighter.  

This isn't rocket science and I often think some of us are overly critical of some of the things Correct Craft did in building their boats.  The long shaft on the Cuda may have been an unorthodox fix to enhance boat performance, but it worked.  

I simply want the original spec so that we have a base line. 

Keep us informed how it works out. 

Bruce 

It sounds and looks like you have the original spec between the picture of Charlie and the measurement numbers from Charlie by way of Pete

What I wonder about is your comment on the rudder port that is not mounted flush but sticks down from the bottom of the hull.

Was that bigger rudder and new port on there before the problem started or was it put on to try and solve the handling issue?

You mentioned Reid thinking that might be the problem, you can add me to that list.

Is it hanging down say 1/4 inch or so with squared off edges or is it tapered so it's at least somewhat hydrodynamically efficient

If you recess it like it was originally built, you'll be back to "baseline" there too

The rudder port is an issue and will be recessed.  It did not cause any problems prior to the engine swap, however.  The problems I noted on page one I know to be from the shortened shaft as I've experienced them with another Cuda.    I tried to install an original rudder port, but the hull has been altered to except the newer style port.  This was done by a PO.  

Plenty of CC's had a lot of strut to prop clearance over the years.

Gen 2 SN's and the Martiniques on that same hull come to mind with over 2 inches of distance.

You have the info you wanted, you know the boat, I'd go with what you think needs to be done right now 

Not to throw a curve ball at you Bruce, but if you look closely at your strut and Charlie's strut they're not the same so any measurements from his may not really be what you're looking for if you're trying to get the prop location in it's original spot.

If you took an inch or so off of Charlie's, it would look like yours

Yes, the struts are different. Looks like you have a 6A and Charlie's is a 6A6. The 6A6 is 1 inch longer at the aft end so, that really puts the prop farther aft. I'd say the aft move was due to CC going to a 13" prop. 

Further aft of what?

They're both 17 ft Barracudas, assuming the transmissions are mounted in the same spot and the struts are in the same spot and you put a 41 inch shaft for example in both, the prop is in the same spot on both boats.

On the boat with a 6A6 it sits closer to the strut by an inch though since the difference in the struts is all at the back. Trim an inch off the back of a 6A6 and it's the same as a 6A

I guess you'll have to explain how that gives any more room for a bigger prop Pete 

Sorry but I'm not a math teacher

Anyway, I appreciate the info and welcome any more measurements I can dig out.  Our original shaft was bent pretty badly, but maybe I can dig it out if it didn't go to the scrap pile.