What have i gotten myself into? Flex Coupling?!?

[brian dragonfly]

after a decade with a 25' northern that had a 9.9 merc off the back (easy maintenance),
i "upgraded" to a 1982 Catalina 30' with an atomic four, last year.

i can't afford a boat in good condition and am quite handy, so i found myself a real fixer-upper. it is in bad shape but, like i said, i can fix most stuff, but also i can spend the money slowly fixing the boat over years, just not all at once up front. (plus it will truly be my custom boat).
the engine, however is a touch intimidating.

the old northern (Firefly) was a dream to handle, but i noticed that the cat30 (Dragonfly) had near zero reverse. pulling into my slip was more about tying-off in time that actual boat handling. stressful, and difficult for a solo-sailor with a new-to-me boat that weighs nearly twice as much.

so i looked into several different prop options that increased reverse thrust.
AutoProp was what i decided on and splurged...

https://www.youtube.com/watch?v=xdxY5Q7wXek

the problem was this... (would like to add picture inline but can't)
ok, so during the transition between forward and reverse... the blades can HIT THE DAMN STRUT!

i need to "lengthen" the prop shaft by about an inch. two ideas have floated up.

A) a custom spacer between the transmission and the coupler.
B) a Flexible Coupling.

i am brand-spanking new to this engine and really could use some advise.
(and not the "return the prop" kind as the ship has sailed. also i am profoundly dyslexic so please ignore spelling, & vids are WAY better than written directions for me.)

here is a guess at a Flexible Coupling i might use from a local (in town) shop (which also has a huge online business if you are in canada)

https://www.marineoutfitters.ca/index.cfm?category=10025|10742&product=63122075

it would add just over an inch (1 11/32) and thus the prop would clear.

i can't find any discussion here about Flex Coupling. pros/cons... that sort of thing.

if i can't figure this out soon, i'll miss the short lived summer here.

also i should change the cutlass bearing... so much to do... and none of the custom tools...

[edwardc]

Hi brian. Welcome to the forum! I think you'll find this one of the most helpful and friendly places on the internet for all things A4.

The Auto Prop sounds like a good idea. Reverse on an A4 is often hampered by two things:

1. The Paragon reversing gear supplies a small (~ 1.2:1) reduction in reverse.
2. Spinning a prop backwards runs it's airfoil (hydrofoil?) the wrong way.

The Auto Prop should eliminate number two. Bear in mind that it's one more moving part to keep maintained.

A spacer is fine IF you have the clearance for it between the output flange of the engine and the beginning of the stuffing box. I don't remember the layout of the Catalina in this area, but others will chime in soon. A flex spacer will also ease the engine alignment requirements.

If there's no room for a spacer (flex or otherwise), you always have the third option of a new, slightly longer, shaft. Could do the cutless bearing at the same time, since that's already on your list.

When you get it all sorted out, one thing you really ought to check is the reverse band adjustment. The A4 uses a friction band to engage reverse, and if its too loose, you get no reverse. In addition, there's NO detent in reverse! You have to hold the shift lever in reverse with pressure in order for it to work.

There are lots of threads here on reverse adjustment. Also look up something called the "Kaminsky modification".

Good luck, and keep us posted on your progress!

[roadnsky]

...one thing you really ought to check is the reverse band adjustment.

There are lots of threads here on reverse adjustment.

Brian-
Another welcome to the Forum!
HERE is a video on the Reverse Gear

vids are WAY better than written directions for me.

HERE are a bunch of videos to fill up your knowledge plate.

I would also recommend that your very first priority is to get the MMI Manual for the A4.

There are a bunch of the crew on this forum with C30's.
They'll be along soon with a wealth of first-hand advice as well.

[brian dragonfly]

thanks for the info.

so i think i have plenty of room for spacer (flex or otherwise) [see attached pict]

a new prop shaft was the first suggestion i heard but it's very cost prohibitive, and labor intensive, as it is highly recommended to get a new coupler and to have it fitted , and ... and... and...

it was the prop maker that suggested the spacer.
the CEO emailed me and apologized directly. turns out there aren't too many cat30's w/ A4 engines in the UK., and i somehow found the flexible coupling stuff and he said it would work. but i thought it wise to tap into the vast knowledge here.

catalina parts are easy to come by, IF you life state-side, which i no longer do. catalina direct has everything.
canada has serious import fees (315CAD for the prop, for example) so i do absolutely everything possible to avoid them. image shipping a new 8foot (or so) prop-shaft/coupler from cali to kingston, on... it might cost in the range of 80billion.

i had tried to order the MMI Manual and an "oil straw attachment thingy" (to help with oil changes, {apparently a foreign concept to the previous owner, judging by the molasses i removed...}), but the shipping costs were more than the goods...

there is a trick i use to ship things to near the border and then drive down and pick them up myself (https://www.kinek.com/)... but the pandemic shot that to pieces. i will absolutely get the book (and oil straw thingy) once things open up.

" When you get it all sorted out, one thing you really ought to check is the reverse band adjustment. The A4 uses a friction band to engage reverse, and if its too loose, you get no reverse. In addition, there's NO detent in reverse! You have to hold the shift lever in reverse with pressure in order for it to work."

um, wow... had no idea...what 'detent' was outside of a campground.
so you have to hold the shifter in reverse or it wont work? (where is the facepalm emoji?)

i'm going to watch the vids now....but just wanted to say thanks.

[brian dragonfly]

Well I got the coupler removed and I slid the shaft back 3/4 of an inch and now the prop clears the strut

but I can't find anywhere that sells a 3&1/2 inch, 3-bolt flex coupler...
Guess it's back to the machinist...

[Al Schober]

I used a 'DriveSaver' from Globe Rubber.

https://www.amazon.ca/Marine-DriveSaver-Flexible-Coupling-Universal/dp/B00GXFFUG0

Coupling itself was fine but I had to change some of the bolts and washers to get it installed.

[tenders]

Whew. $540 at Defender ($497 if you're a "Defender 1st Member"):

https://www.defender.com/product.jsp?id=99532

[ndutton]

And a new shaft is how much?

[edwardc]

A 3/4” thick circular steel spacer with three through holes and a little depression in the center to mate with the coupler face should be an easy diy build for a hobbiest with a lathe and a drill press.