Upgrade to a Gas Spring-Operated Outboard Motor Mount

 

Do you have a heavy four-stroke outboard motor on your sailboat? Is it a chore to raise and lower with your current motor mount? Maybe you have a back injury that makes lifting a risky behavior. What about your first mate, can they raise and lower the motor if they need to? All these are good reasons to consider whether your current motor mount is adequate for your needs.

Before I get started, a bit of legal housekeeping. This post contains affiliate links. That means I receive a small commission if you make a purchase using these links. You can purchase the products anywhere you like, of course. For a complete explanation of why I’m telling you this and how you can support this blog without paying more, please read my full disclosure.

Summer Dance has a 2004 Yamaha 8 HP long shaft outboard motor (model F8MLHC) that weighs 87 pounds. When we bought her, the outboard was mounted on the original equipment Garhauer-made two-spring motor mount. (Incidentally, this motor does a great job of charging a deep cycle battery when you add a rectifier/regulator to it.)

Yamaha F8MLHC outboard
The excellent Yamaha F8MLHC outboard

My achy breaky back

The Garhauer mount is rated for up to 80 pounds but I think the springs have lost some of their strength over the years. Before I replaced it, hoisting the motor up out of the water wasn’t an easy task – there was way more than the 7 pound difference between the motor weight and the mount rating. Other than that, it’s a good mount and has held up well over 34 years.

It wouldn’t be so bad if the motor were closer to the top of the sternrail but in its lowered position, I had to lean way over the sternrail to grab the mount handle and hoist the motor up. With apology to Billy Ray Cyrus, I don’t recommend it if you have herniated disks and a broken vertebra like me. It was becoming such a chore that I started looking for a way to spend more time enjoying sailing and less time nursing my back.

BEFORE - Original equipment two-spring outboard motor mount. The dangling cable is a safety lanyard that attaches to the motor
BEFORE – Original equipment two-spring outboard motor mount. The dangling cable is a safety lanyard that attaches to the motor. Also shown are my homemade telescoping mast stepper and prototype stern perch seat.

The way these mounts are built, it’s impossible to simply add more springs to them. That would have been my first choice for a solution but the tubes that the springs are assembled on are welded together. Except for cutting and re-welding them, there’s no way to add more springs.

OMC, gone but not forgotten

Rather than replace the mount with a different model with more springs, I decided to look for an alternative design. I remembered reading on the Chip Ahoy blog how Chip added the missing gas spring to his OMC Auxiliary Motor Bracket. OMC is no longer in business and the motor bracket is no longer in production, but used ones appear regularly on eBay. It looked like a solid design and easier to use, so I started watching for a bargain. By the way, the corporate history of OMC is an interesting story in itself.

DSCN2453
OMC mount after refurbishing and ready to install

The OMC design is similar to that of most other outboard motor mounts, control arms in a sliding parallelogram arrangement that keeps the outboard motor vertical as it is raised and lowered. It works on the same principle as the front suspensions of most cars. But it’s also different from other mounts in several ways.

First, instead of stainless steel, the major parts are made of plate and cast aluminum painted white. Second, instead of a large handle that actuates the latching mechanism, there’s a small, spring-actuating lever. And last but most importantly, instead of multiple coil springs to compensate for the motor weight, it has a single gas spring. Gas springs provide more consistent force throughout their range of motion than coil springs.

To use the OMC mount, you just flip the lever to the opposite of its current position to disengage the latch. This transfers most of the weight of the motor to the gas spring so that you can easily push or pull the motor into position until the latch re-engages. A video at the end of this post shows how.

Refurbishing tips

When a used OMC mount appeared on eBay at a really low price, I bought it almost immediately. It arrived in very good condition and looked like it had been used relatively little.

First, I disassembled the mount, refinished the oak board, cleaned all the parts (Mr. Clean Magic Eraser Cleaning Pads work great on oxidized paint and stubborn stains), polished the hardware (I like Flitz), and replaced half of the Nylon bushings on which the parts rotate.

Disassembled motor mount
Disassembled motor mount

If you decide to refurbish one, don’t try to buy the OEM bushings (part numbers 25 and 27 in the diagram below) from a marine parts retailer. Part #25 is no longer available and for #27, marine retailers are asking $9-$10 EACH!

Exploded parts diagram
Exploded parts diagram

Instead, order standard 5/16″ ID flanged clip Polymer bearings (part G0242636) from an industrial supply company like Zoro.com for $1.95 per pack of 5. They will replace parts #27 (4 required). If you want to also replace the bushings at part #15 (2 required) or #25 (2 required), consider standard 3/8″ ID flanged clip Polymer bearings (part G0270837, $2.52 per pack of 5).

DSCN2033
Worn bushings (top) and new replacements (bottom)

Transom mounting tricks

With the OMC mount reassembled, it was ready to replace the old Garhauer mount. Unfortunately, the OMC mount doesn’t have the same bolt pattern as the Garhauer mount, 6″ x 7″. The OMC mounting bolts are spaced on a 5-1/2″ x 7″ pattern. I resolved the difference by elongating the bracket holes horizontally by 1/4″ each.

Mounting holes narrowed 1/4" on each side
Mounting holes narrowed 1/4″ on each side

The Garhauer mount on Summer Dance used six bolts through the transom because the previous owner wanted to raise the motor for some reason. Most C-22s only use four like the OMC mount. I’m not concerned about it being weak, though, because of the aluminum angle brackets that I installed on the inside of the transom to reinforce it for trailering with the outboard motor mounted. (The picture below is of the brackets installed with the old motor mount.)

Outboard motor mount reinforcements inside the transom
Outboard motor mount reinforcements inside the transom. Double nuts guarantee against loosening

After the bracket hole modification, I reused the old mounting fasteners and the angle brackets to install the OMC mount in the existing holes in the transom.

How’s it work? See for yourself in this video.

Other considerations

Here are a few other points to keep in mind with this mount.

The OMC mount has less vertical travel than the Garhauer mount so be sure your outboard motor will sit low enough in the water to prevent cavitation. If not, you might have to drill new holes in the transom to attach it lower than your old mount.

Without the outboard motor attached, the OMC mount rattles a bit in the raised position, not due to worn parts but by design. The latch rod and the slot through which it travels are not a close fit on purpose. The raised position is also where the gas cylinder does not apply any pressure. To prevent the rattling while trailering, put the mount in its lowered position to apply pressure from the gas cylinder. If you trailer like I do with your outboard mounted, the weight of the motor prevents rattling.

The Bottom Line

Suggested price: $353.95
$tingy Sailor cost: $53.68
Savings: $300.27

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10 Comments Add yours

  1. Bonj says:

    I couldn’t vote in your poll because my motor (a 4HP 4stroke long shaft Yamaha (less than a year old)) sits on a fixed mount. I pull it out of the water using the Yamaha’s own tilt mechanism. The 4HP is light enough to do that single handed, although I always have help to mount the motor on sailing days. It only has to push a 16ft boat, so it does a decent job.

  2. Richie says:

    Great information and love the site. Really inspiring. I’m using your jig method for refinishing my teak now. Saw the same bracket for 24.99 on ebay today.

  3. Peter nelson-Davis says:

    OMC mount looks great but not sure if I’ll find one in Australia. To help with the lift of my Honda BF8 (40kg) I relaced the weak spring with 2 upgraded springs from the local farmers supplies. Takes all but about 10kg – great. To help with the lift when raising the motor from the cockpit i have a short rope. I also have a webbing harness that fits around the motor with a lifting ring that works quite well. Can’t find the website at present and the blurb is on the boat. I’ll try and add that in the future.

  4. Joanne says:

    This past spring I needed a new outboard motor. I opted for a 9.8 Tohatsu model with power tilt. I too had to lean over the stern rail, unlock the button and hoist up my old Yamaha horizontally on the bracket. Now, I just push a button and the engine tilts up out of the water….so much easier! I can still opt to pull the bracket up vertically to change height positions of the motor, but it’s the horizontal power tilt with a push of a button that sold me!!

    1. It doesn’t get any easier than that!

  5. Ed in Gig Harbor says:

    At my current stage of Venture 21 restoration work, I am not yet sure how my mount will work with my 6 HP Yamaha. It is a standard shaft, as was my old 7.5 HP Sears Gamefisher, used when Simran was last afloat. I have no stern railing, so that made access and use easier. That brings me to my questions:
    1) Access to my mount bolts requires a challenging crawl beneath the cockpit seats and some shuffling of foam blocks. I’d love to add a locker on one or both sides. Do you have any posts or experience on adding such? I have seen to creative use of screw in/out inspection ports that would be another somewhat limited solution (no locker funtion).
    2) I was out in rough water once (not intended – long story) where cavitation raised the old engine out of the water. I am sure the racing when the propeller was out of the water, not to mention inability to suck in cooling water, was not great for the motor. Have you seen folks convert a regular shaft to a long one and would that gain enough to keep it in the water in most conditions? (I’d not be out sailing if the waves are large with foaming whitecaps!)

    Thanks for the great posts and resources!

    1. Hi, Ed

      Gig Harbor is one of the beautiful places I’m looking forward to visiting someday.

      1) It’s a claustrophobic crawl in a C-22 too, so I know what you mean. I too have seen where other owners have used inspection ports to get at those spots but I’m not keen on them if there’s another way that doesn’t require cutting holes. If I didn’t already have lockers in my C-22 but wanted to add them, I’d first consider vertical water-tight hatches and leave the seat surfaces intact. You might find somebody online that has made the kind of modification before.

      2) Sorry, I haven’t come across any conversions from short shaft to long shaft. Most guys just replace the outboard entirely or lower the mount to keep the prop in the water under more conditions. This is one scenario where I’d opt for making new mounting holes in the hull. That, in turn, places the motor lower on the transom, which makes it more of a grunt to raise, hence the reason for this article.

      I hope that helps a little,
      $tingy

      1. Ed in Gig Harbor says:

        Thanks, $tingy. I, too, am a bit concerned about water getting in via a ‘custom’ locker or inspection port, and about structural rigidity. Doing it on a vertical surface does make sense, especially for a port.

        Yes, the ‘Harbor’ is pictuesque and there are many opportunities for additional exploration in the South Puget Sound (San Juans is what you hear about most often)…lots of ramps for trailer-sailors, too! If you head this way, give me a shout!

        Cheers, Ed

  6. Neil Tomkinson says:

    I just bought a little 15 foot cat boat which has this mount on it. I’m pretty sure the gas shock is shot, it will not lift the bracket with no motor on it. Is that gas strut available?

    Thanks,
    Neil

    1. Hello, Neil

      Apparently, the strut is still available for around $200. If the mount still rotates freely, you might try adding compressed air through the Shrader valve on the end. I’ve heard of other owners that worked for. Or you can try finding another used mount on eBay or craigslist like I did. Just be sure it works correctly before you buy.

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