Transom bolts bending. CMC jackplate laying over!

[Revolution141]

Bought a Cmc hydraulic jackplate 2.5 years ago. Have had problems from day one with plate dropping on port side. Spoke to dealer who said I needed upgraded plastic guides and aluminium outer plates (replaces washers) after swearing to me over the phone that this was the plate I needed for my application. I made it very clear I was racing my 21' v hull with 300xs offshore and it would cop a hiding. When I ring him back to tell him of the problems I'm having he treats me like an idiot for not buying the stainless version??? Sells me upgraded guides anyway and assures me it will fix my problem. Needless to say nothing has changed and it got to the point now I have drilled and tapped holes through side of plate to bolt off level. Can't adjust with hydraulics now though. Anyone with similar issues?What size mounting bolts are 300xs owners using through transom? I'm on my 3rd set of 1/2" stainless bolts as they keep bending. Want to go to larger diameter bolts but can't cause my heap of junk jack plate doesn't have enough clearance for bigger nuts and bolts.

[BUSHWACKER]

If I were you I would contact CMC direct.

[danrad]

Have a friend that kept stretching the SS boats at the transom causing the jackplate to move on the transom. He swithed to aircraft grade steel boats. He never had the problem again.

[Euroski]

Have a friend that kept stretching the SS boats at the transom causing the jackplate to move on the transom. He swithed to aircraft grade steel boats. He never had the problem again.

I would do that... was told SS bolts are soft compared to steel bolts.

[VELOCITOY]

SS bolts are a no-no in a high-strength/high-torque/sheer application...Fastenal has what you need in the industrial section of the catalogue...never did like the CMC stuff...

[myron]

Allisons come with 9/16 fine thread bolts on the top

[Bryan1257]

uh oh, just put 1/2 all thread rods 10 inches long on my bracket today! However I was just makin sure everything lined up.

[fast fun 2]

Weve used CMC stuff on a few offshore race boats, no issues. Call CMC direct

[Revolution141]

Funny.... Merc supply the motor with 1/2" stainless bolts for rigging????The other thing that ****s me is the holes in trim bracket are sloppy for 1/2" bolts. I know they can't be exactly 1/2" or bolts would be almost impossible to line up but still I think the holes are a fraction too big. Merc 6 drives use stainless studs to mount also.I know some offshore race cats that use the high tensile steel bolts but they also need replacing every 12 months cause they rust.I'm sure bigger stainless bolts would solve my problem. Will probably just cut my loses with this heap of $hit jack plate and make something myself.

[spbutler]

I have a CMC that is probably at least 10 years old and have had no problems. I'm not sure what size bolts and what they are made of but they aren't stainless. Are you using lock washers and big enough backing plates.
As everyone else said call CMC. I don't think I have any play in my holes.

HYDRAULIC UNIT

(Item Numbers - 65001, 65002, 65006, 65201,61001, 61002 and 61006)

1. One Hydraulic Power-Lift unit2. One wire assembly3. One Power-Lift position indicator gauge(65001, 65006, 65201, 61001, and 61006)4. One Power Dial Control (65006 and 61006)5. Four 1/2" -13 x 3 stainless steel hex head cap screws6. Four 1/2" -13 stainless steel hex nuts7. Four 1/2" stainless steel lock washers

8. Four 1/2" stainless steel flat washers

[modvp]

What type of stainless steel bolts are you using? If you're using type 316 SS, I would consider using 304 SS. 316 is more resistant to corrosion due to the presence of molybdenum, higher nickle and lower chromium content but it makes for a slightly "softer" bolt. 304 (lacks molybdenum), and due to it's slightly higher chromium and lower nickle content makes for a stronger bolt. For that reason, I opted to use 304 SS for my transom/jack plate bolts.

[FUJIMO]

Its become more common that a rigger, when drilling a transom for a new outboard bracket, jackplate, I/O transomplate, large swim platform, etc., to drill larger size holes than are needed for a particular size mounting bolt. It makes it easier for them, given the large number of nuts, bolts & washers that have to go in at the same time, "and line up", all with caulking on them, to slip right in, without having to use a hammer. This is common practice these days. With this said, my experience with offshore outboard race boats has found, that NO brand of single engine "adjustable" aluminum setback bracket, hydraulic OR manual, can take the brutality of offshore abuse. In a race that requires you first, to finish, they just don't cut the mustard. The bolts that hold them on, are just part of the bigger problem.

[loop]

316 or 304ss is not strong enough for his application
use 17-4 stainless bolts or studs. MUCH stronger and corrosion resistant too.
If not use grade 8 steel

[modvp]

What type of stainless steel bolts are you using? If you're using type 316 SS, I would consider using 304 SS. 316 is more resistant to corrosion due to the presence of molybdenum, higher nickle and lower chromium content but it makes for a slightly "softer" bolt. 304 (lacks molybdenum), and due to it's slightly higher chromium and lower nickle content makes for a stronger bolt. For that reason, I opted to use 304 SS for my transom/jack plate bolts.

I checked my bolts, I have the numbers mixed up...I am using 316...not 304. I had 304 SS and changed to 316. I would definitely consider using something harder like what was suggested by loop.

[Greg G]

Go to 17-4 for that application ...........