Determining Shaft length on a Zodiac FC470 - Page 3

Projectile · 07 July 2014, 05:34

I have a Zodiac WB465, which is similar to an FC 470 but without speed tubes. My transom measured 19 inches, and my Evindrude ETEC was a long shaft that measured 22 inches to the AV plate. Accordingly, my AV plate was 3 inches below the bottom of the transom.

I had horrible performance issues that are perfectly explained by a hook in the hull. Unfortunately, my dealer incorrectly assembled the floorboards, which would have hooked the hull, and this went unnoticed. The boat was correctly assembled at the same time that the transom was plated to raise the motor so that the AV plate now sits 1/2-3/4 inch below transom bottom. The bow steering is much, much better, but now, I get plenty of prop ventilation - as if the motor is too high. I now wish that I could easily try to lower the motor, but to do so now is a big job because the transom was plated to this height.

Based on my experience, I would not raise your motor so much (4 inches!). I'd consider raising it 3 (or less), and leave the possibility to raise it another inch by placing a 1 inch block of wood above whatever you build to raise it. It's easier to do that than to have to reposition the device you will use to raise the transom, no?

Part of me thinks that Zodiac makes these transoms < 20 inches for a reason. Ie. They are supposed to run with the AV plate a little lower than on conventional hulls. Maybe that's wishful thinking.

SIBRider has done what you are doing. You should see his pics.

I'm very keen to hear how this turns out for you.

F470 · 07 July 2014, 21:29

Thanks for the input. My AV plate is currently 4.75" below the hull. If I raise the motor per drawings (4.375") it will be 0.4" below the hull. I suppose I could have it slightly lower (0.75" below) and an extra set of holes wouldn't hurt so I can drop it another 1/2" if need be.

F470 · 09 July 2014, 03:31

I'm considering making it adjustable with 3 half inch steps. What height do you think should be the neutral position? Should the neutral position be flush AV plate/hull or 1" below? I know on a normal boat without speed tubes it is supposed to be flush but am I correct to assume that the FC470 can ride a little lower as default position due to the speed tubes? Clearly from my own experience 4.75" below is way off but how would 1-2" work? What height are yours currently at?

I'm considering these adjustability options.

Option a) 0", 0.5" and 1" below hull
Option b) 0.5", 1" and 1.5" below hull
Option c) 1", 1.5" and 2" below hull

Please vote

F470 · 09 July 2014, 03:33

Or option d) 0", 1" and 2".

F470 · 09 July 2014, 04:58

Here's a screenshot of the adjustable transom riser. Shown here with a 0", 1" and 2" drop of AV plate below hull.

Projectile · 09 July 2014, 05:03

Why not have the middle or highest position where SIBRider has his? He also has an FC470 ...

If I had to pick, I'd go with B.

F470 · 09 July 2014, 05:09

I don't know what he has other than judging from the picture it looks like about 0.5" below the hull.

SIBRider · 09 July 2014, 07:41

What size bolt do you plan to use? Step must be larger than diameter of bolt hole otherwise holes will touch making a slot. So for 0.5" bolt you would need at least 0.75" step. IMHO there is no point going much more than 1" below. I'd go with +0.25 -0.5 -1.25. Make sure you set it up at 90 degree motor to water surface trim position, approximately 15 degrees angle between motor and transom.

Mine is 0.5" below or so.

F470 · 09 July 2014, 17:23

Thanks! I like the idea of 0.75" increments. 0.5" seems small. You mentioned +0.25". Would you really want the AV to be slightly above the the hull on a Zodiac?

F470 · 09 July 2014, 17:26

The ones in the CAD model are 5/16". Too small? I use larger ones for the ones that don't hold the motor down as I am limited by what can pass through the motor mount holes.

SIBRider · 09 July 2014, 17:54

Quote:

Originally Posted by F470

Thanks! I like the idea of 0.75" increments. 0.5" seems small. You mentioned +0.25". Would you really want the AV to be slightly above the the hull on a Zodiac?

As a matter of experiment why not. You got bigger motor/prop.

Quote:

The ones in the CAD model are 5/16". Too small? I use larger ones for the ones that don't hold the motor down as I am limited by what can pass through the motor mount holes.

I think motor mounting bolts on Zuk are at least M10. At least mine are. 5/16 or M8 are somewhat undersized unless you use more of them

F470 · 09 July 2014, 18:23

True. It is an experiment.

F470 · 09 July 2014, 20:57

Here's where I landed. Thanks for all the input. At 0.75" increments with 3/8" bolts there will be enough distance to fit a open end wrench but not a box wrench or socket. At 1" increments you can fit all. Don't think that should matter. This set up gives a 5" maximum rise. Since my offset is 4.75" the settings will be: +0.25", -0.75" and -1.5".

SIBRider · 09 July 2014, 21:38

I wouldn't do two bolts side by side. It's not going to do any good. Also one thing having small gap drilling metal plate another through wooden transom. Drill bit tends to wonder a bit in wood. Hard to drill exactly perpendicular. You may want to have holes drilled only in one plate then use those as guide to drill transom and opposite plate. I'm a little concerned that you only have bolts at the bottom. Top ones only clamp (I guess) which is never very reliable.

F470 · 10 July 2014, 00:23

I addressed the bolts that were too close to each other. As is there are 6 x 3/8" bolts going through the transom. Is that sufficient? If I go up in size it'll interfere with the adjustability pattern so in that case I would rather add two more in the center but that seems a little overkill. I hear you on the drilling but I'd rather have all these holes water-jet cut and use them as a guide. That way I can trill halfway though from either side as perpendicular as possible. Or I could fab a guide rod for the bit to go through

SIBRider · 10 July 2014, 16:39

How do you plan to attach motor, I'm guessing 4 bolts: 2 narrow in the middle and 2 at very top? Motor bracket has slots at bottom for adjusting height. Does its length match your adjustment range? If not you will have to drill extra holes in transom. Actually If you use 4 bolts to attach motor then you don't need to move your raiser up and down at all it can be left static, only motor and 2 top bolts need to go up and down. Your raiser doesn't have to be as tall either in that case. Clamps are not needed if you bolt it down with all 4.

F470 · 10 July 2014, 21:23

I can't check the motor until tomorrow but as far as I recall there are only two holes on the motor meant for bolt mounting. Two holes in addition to the two clamps. So unless I am mistaken I am going to have to use the clamps and the two mounting holes with bolts to mount it. Those two holes are about 9MM wide x 32MM tall so a about 1 1/2" in adjustability up/down. I can check closer tomorrow.

I'm not sure I follow the rest of what you're saying. Are you saying that I could leave the riser static and have the motor move up/down? Wouldn't that leave a gap between motor mount and transom? Seems like you would want the motor to rest its weight on the transom instead of bolts, at all times. I also don't see how I could make it any less tall. It needs to have a total rise of 5".

SIBRider · 11 July 2014, 16:51

1980 DT40 bit different bracket from 83+. Bolts are indeed M8. Slot (at least in graphic) is what limits adjust ability if bolted to transom. If it is not a slot but rather a hole then you can't move motor higher without drilling corresponding new pair of holes in transom. I suppose you can dial in height of outboard by adjusting raiser with outboard on clamps. Then once you found desired height drill transom to secure outboard using single pair of holes as guides.

F470 · 11 July 2014, 17:01

Doh! I finally see what you're saying. I can't believe I haven't caught this until now. Of course the adjustment level is limited to the range of that slot otherwise I would have to drill more holes in the transom. So I will see if I can change the design to work around this. The total adjustment will then go from 2" to 1.5" unless I want to drill more holes in the transom. Thanks!

SIBRider · 11 July 2014, 17:24

Taking a clew from outboards you can make slot in lower corners of raiser instead of holes and move your assembly (with some effort) without taking it complete apart. Remove upper loosen lower bolts you could slide it up and down with certainty that it won't fall off even with outboard mounted.