Determining Shaft length on a Zodiac FC470

[Projectile]

Whatever you guys come up with, patent it! I'm sure many inflatable owners would find it useful.

[SIBRider]

there are quite a few manual and not jack plates available already.

[F470]

I have quite a few patents. Its been a fun exercise but I don't think this one is worth the investment in terms of patent. There are a lot of solutions out there but none are specific to FC-470's so the best reason to make one as far as I can tell is to make it fit specifically to the particular transom thickness and shaft length requirements of a FC-470. The nicest one I found was made by a guy named Tom C a few years ago called TSG Jack plates but he no longer makes them. Here's a link. His design is much better than mine because it provides a much higher range of adjustment. My design as is, if I choose to have the motor bolted through the transom will only provide 0.91" range of adjustment so at that point you can ask yourself if it's worth the effort to make it adjustable to begin with.

[F470]

I'm running out of time so I have decided to buy a jack plate instead. I'm looking at the Detwiler D1000 (JP1040) which has a setback of 4" but I cannot find the maximum vertical adjustment anywhere and I haven't heard back from the company. Any guess as to what the vertical adjustment might be on this model? Does perhaps even someone on here own it?

[SIBRider]

It's not going to work as it is. Those kind of plates are much larger then it seems from pictures. It interferes with deck drains as is. Has to be modified a bit to fit nothing too major. I have brand new very similar design (no black anodizing) 3" setback 4" height adjustment. Got it to research that hot topic of "AV/DP water flows". Unfortunately free time is not on my side. Don't know if I get to it this summer. Way too busy. If you want to tinker with it or check it out let me know today. Heading south tonight to climb Shasta then gone all next week.

[F470]

You're right. I just heard back from them. Back to the drawing board. I would live to see what are willing to share but I am booked today. I will send you a PM with email address, if you have time to send a few pictures that would be very helpful. Have fun at Shasta!

[Doug_G]

[jyasaki]

Other thing to watch if you're setting the motor back is interference from the transom when you tilt the motor.

jky

[Attack Ducks]

I'm running into this problem on my current rig which is the 1999-up "long shaft" transom design like yours. Previously I have run AML35 short shaft motor on the older notched transom "short shaft" F470s as well as various long-shaft outboards on the same "short shaft" F470s in combination with the CMK Transom Cap which essentially turns the "short shaft" transom to a "long shaft" one and never had these problems. However with my current setup I am experiencing water flowing over transom into boat at cruise unless trimmed excessively out and lower top speed than I should be getting with this big a motor on a 300# rubber boat. I am currently running a 20" shaft motor raised one bolt hole position above "flat to the transom" level which appeared to put my cav plate at the same level as the transom bottom/keel but it isn't enough. I was planning on raising it another bolt hole position this weekend and testing the result. This whole rig was an experiment anyway to see how far I can take the platform (build thread coming soon) and surprisingly this is the only issue I've run into...it's also the only issue I didn't anticipate :-/

I have been around boats all my life but never encountered this before so I too am learning as I go on this. Its just really hard to see what it going on back there while underway. My concern is if it gets too high you can get an air pocket around the water pump inlet, reducing cooling flow and possibly overheating the motor. An adjustable jack plate would be the answer but seems overkill, however it is a PITA to do this "trial and error" style.

If you do make an "extension" plate I would suggest making it wider to spread the fore/aft twisting force along as much of the transom as possible and not concentrating it all in the middle. I have seen plenty of broken/cracked transoms on F470s, although I'd guess a lot of those were from airdrops gone bad I still wouldn't temp fate.

[SIBRider]

Yamaha 90 is one big motor for F470.

[Attack Ducks]

Originally Posted by SIBRider

Yamaha 90 is one big motor for F470.

Well it is and it isn't. HP yes, on paper, no question. Weight, not so much. It went down like this... I've run up through 55hp motors on these boats and was left wanting a little more power. With the hard deck the F470 is rated for 65hp, which isn't very common so I began looking for good deal on a Yamaha 70 hp 2stroke. After searching the better part of a year I came across a great deal on the 90, which is pretty much the same as the 70 (size, weight, etc) just more HP. In fact the Yamaha 70/90 weight is about the same as the Johnson 55hp Enforcer and my previous favorite Honda BF50...around 230#...so the 90hp motor isn't making it any more stern-heavy than the other commonly-used motors. So I figured I'd "try" it. If it turned out to be too much, I'd sell it and go back to plan A. Plus I could always install a throttle stop, right? (BTW, psychologists call this process "rationalizing" lol)

The newer F470s like mine have a straight transom with SUBSTANTIALLY beefed up mounting to the tubes (Zodiac calls them "Ovoid transom reinforcement patches"), furthermore I have all the components of the CMK installed: the stainless transom cap, the one piece solid stringers and the thrustboard reinforcement plates. I also added fittings to attach torque rods between the transom and aluminum hard deck to prevent excessive stress on the transom attachment. Finally, I run SeaStar full hydraulic steering. Long story short, the 90 is working fine on this particular F470. I've been running this setup for about 4 yrs now and other than the aforementioned transom backwash issue, I haven't observed any issues: No excessive fatigue on the transom or boat hull and no "scary" behavior—even at WOT in rough water.

Despite those assurances, I'm sure there will be those that disapprove of my setup. For those people, take solace in the fact I do plan to repower in the future. Yamaha finally came out with a lightweight (~250#) 70hp 4-stroke last year that I would like to eventually throw on the back on this boat. Then I can hang the 90 off the back of a 5.4m RIB

All this is probably better located in my build thread...as soon as I get around to starting it I'll move it there.

[SIBRider]

Sounds good to me.

[Attack Ducks]

Originally Posted by SIBRider

Sounds good to me.

Sorry for that somewhat lengthy response. I'm new here and not quite sure to expect yet... Truth be told I lost interest in the boats for a while and building this rig has rekindled my interest. I set out to build a flexible platform that I could SCUBA dive off one day and chase my PWC-owning friends around the lake the next and pretty much succeeded...this boat is a blast to drive.

I do have another FC470 I plan on keeping simple...just a roll up deck, co2 inflation, 6 gal fuel bladder and a small tiller outboard (25-35hp). Actually I'd love to get a FC420 but they seem to be as rare as hens teeth (anyone want to trade? ;-) )

[Squid Boat]

Originally Posted by Attack Ducks

Sorry for that somewhat lengthy response. I'm new here and not quite sure to expect yet... Truth be told I lost interest in the boats for a while and building this rig has rekindled my interest. I set out to build a flexible platform that I could SCUBA dive off one day and chase my PWC-owning friends around the lake the next and pretty much succeeded...this boat is a blast to drive.

I do have another FC470 I plan on keeping simple...just a roll up deck, co2 inflation, 6 gal fuel bladder and a small tiller outboard (25-35hp). Actually I'd love to get a FC420 but they seem to be as rare as hens teeth (anyone want to trade? ;-) )

You can't run a bigin....''You'll shoot your eye out''.

Carry on..

[Attack Ducks]

An update on my experience... I went out this morning and raised my motor again. Unfortunately, the original holes through the transom were drilled 2nd down from top because at the time I never expected I would need to raise the motor (never had to before) . Previously I raised it one hole. So today its now two holes above flat on the transom. Unfortunately that's not enough I never really looked at it with the motor tilted down on the trailer until today...it's clearly too high, not sure how I never noticed this before. Looks like it needs to come up another 2" to be even with bottom of transom. To do it right I need to take the transom cap off and raise that also, inserting a suitable filler in the deadspace above the transom...which means removing the motor...fun!

The upside is the boat ran noticeably better today...much less splash over the transom than last weekend. I had an extra person in the boat today plus 16 gal of gas and some gear that I didn't carry last weekend. Despite that and the fact that the lake was choppy as heck (holiday weekend) I gained 3-4 mph top speed compared to last weekend. Some of that I attribute to running some seafoam through the motor yesterday to clean out the carb jets & carbon buildup...but I'd say 1-2 mph was just from raising the motor. Really curious to see how it does whien I find the "sweet spot" which I will be doing soon since I have to derig it anyway to fix a speed tube sheath (more on that in another thread). If it's not one thing, it's another!

[jyasaki]

Originally Posted by Attack Ducks

If it's not one thing, it's another!

Well, yeah; it's a boat. The only time you don't have something to work on is when you've sold it.

jky

[prairie tuber]

Originally Posted by Attack Ducks

Despite those assurances, I'm sure there will be those that disapprove of my setup. For those people, take solace in the fact I do plan to repower in the future. Yamaha finally came out with a lightweight (~250#) 70hp 4-stroke last year that I would like to eventually throw on the back on this boat. Then I can hang the 90 off the back of a 5.4m RIB

All this is probably better located in my build thread...as soon as I get around to starting it I'll move it there.

If you do go to the Yam 70hp 4-stroke - I'd like to hear your thoughts on it. It will still be a while before I upgrade from my Yam 40hp 2-stroke, but that new Yam 70hp 4-str is on my short list, as well as a 65hp ETEC commercial and a Honda DF60. Am wanting to stay within the max that is rated on the transom plate which is 60kw (~80hp). Would want to stay with a tiller set up for me.

[Stickyfingers427]

I just got an FC 470 2 weeks ago from one of my local fire departments. There’s a Mercury Mariner 60 on it and a light weight center console that you sit on it like a motorcycle .. The engine seems to run beautifully but there is a massive amount of splashing going on back into the boat. It’s a 20 inch shaft end it looks like I definitely need to raise it. Top speed was only 27 miles an hour and sucking gas like crazy. I’d like to know from other people what size engine they’re running and what their top speeds are so I can kind of judge where I should be.

[cgoing]

Most F 470’s were built with 18” transoms by design. Much older ones with 15” and some newer ones are actually a full 20”.

[skip3662]

Hi are
You still around, I wanted to ask about the CMK capping plate.