Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
msteinkampf
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Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby msteinkampf » Sun Dec 18, 2022 8:17 pm

Installing an Atlas Micro Jacker Hydraulic Jack Plate on a MONTAUK 17
This article will describe and illustrate the installation of an Atlas Micro Jacker hydraulic jack plate on my 1990 Montauk 17 with 1991 Mercury 90-HP outboard.

I mostly use my MONTAUK 17 boat for coastal saltwater fishing in Terrebonne Parish, Louisiana. A typical trip includes running through shallow channels in salt marsh followed by a 12-mile run across a bay to reach a barrier island that is surrounded by shallow water. I have come to realize that a hydraulic jack plate would help me deal with choppy bay waters while making it easier to maneuver in the shallows without excessive engine trim.

This is more than a convenience: I once returned from an afternoon trip during a falling tide to find that the channel I had previously used was no longer navigable, and I wandered through the marsh in the dark for an hour until I found my way back to deeper water. By this time, I had sucked up so much mud into the engine that I wound up blowing a cylinder due to overheating.

I have read a Cetacea article about putting brackets or jack plates on MONTAUK 17 boats, but I have not been able to find any information about installing a lightweight hydraulic jack plate on a Montauk 17.

I’ve worked on my boat a fair amount over the years, including replacing most of the electrical components, the water pump, and the outboard engine lower unit, and even rebuilding the outboard engine powerhead after my disastrous adventure in the marsh, but I had never paid much attention to how the motor was attached to the boat. On careful inspection, I noticed a few unusual features as seen in Figure 1.

Atlas 1.jpg
Figure 1. Transom of Montauk 17. Note the asymmetry of the splash well drain holes.
Atlas 1.jpg (76.06 KiB) Viewed 3897 times


  • The engine was mounted two-holes up with the anti-ventilation plate about 1-1/8-inches above the keel, despite both the owner’s manual and the OEM service manual recommending the plate be even with the keel.
  • The port splash well drain is installed about one inch closer to the centerline than the starboard drain.
  • The lower engine bracket bolts are installed using the topmost holes in the bracket, even though there was room in the splash well for the bolts to be lower.
  • There is a flange on the port side of the engine bracket that prevented my dealer from installing the engine any lower than it is without hitting the splashwell drain on that side. This flange doesn’t appear in any of the photos in the service manual, and it doesn’t seem to have any function.

Although I might have been unhappy if I had noticed these peculiarities when I bought the boat, the installation has worked well for me, with good engine performance and mounting bolts in the transom that were never immersed in water. Now, I run this boat with a fair amount of weight at the stern. Although the main engine isn’t heavy at 283-lbs, I typically carry two AGM batteries the weigh 42-lbs each at the stern, an 18-lbs trolling motor mounted on the transom, an assortment of tackle boxes, live wells, and ice chests on the rear deck, and 24-gallons of gasoline fuel under the Reversible Pilot Seat.

I wasn’t interested in putting a heavy jack plate on the transom, but when I saw the specs on the Atlas Micro Jacker at a weight of 23 lbs and rated for use with outboards up to 425-lbs or 115-HP, I thought it was perfect for my application. Indeed, one expert well known to this forum, Tom W. Clark stated
Tom Clark wrote:If I were going to install a jack plate on a small Whaler, the Atlas Micro Jacker is it.
I wound up buying the jack plate from Home Depot Online because it was about the same price as on Amazon, and I had a coupon for 10% off.

Atlas 2.jpg
Figure 2. The Atlas Micro Jacker weighed about 2-lbs over specific weight.
Atlas 2.jpg (34.27 KiB) Viewed 3897 times


Of course, the biggest challenge to installing a jack plate is removing the outboard engine from the transom. I already had a lifting ring from when I had removed the powerhead, so I constructed a gantry crane using some scrap lumber and a sturdy portable chin-up bar I had built a few months ago. I had planned to use a cable winch puller, but a simple piece of chain was satisfactory; I could easily control the tension on the chain by cranking the trailer jack up or down.

Atlas 3.jpg
Figure 3. Gantry crane for engine removal.
Atlas 3.jpg (75.66 KiB) Viewed 3897 times


Next step: Removing the 90-HP engine and test-fitting the jack plate to the transom.
1990 Montauk 17’ w 1991 Mercury 90 HP outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards

jimh
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Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby jimh » Mon Dec 19, 2022 9:05 am

That the weight of the Atlas Micro Jacker is only 25-lbs and there is a hydraulic lifting cylinder is quite impressive.

Also, your "scrap lumber" pile must be quite well stocked to be able to create that gallows hoist. Nice work.

I am looking forward to the next installment in this article.

msteinkampf
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Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby msteinkampf » Wed Dec 21, 2022 4:56 pm

Removing the 1991 Mercury 90-HP outboard engine from the transom was a bit intimidating because I had no engine hoist or forklift available. I used just a reinforced chin-up bar and a chain, and I was doing this job solo. The process became much easier when I realized that I could tell how much pressure there was on the chain by examining the top of the engine swivel bracket. When I could see the swivel pin, I knew the engine’s weight was being supported by the gantry.

Engine lift pic.jpg
Figure 4. The close-up at A shows the engine swivel tube before the engine weight has been taken up by the lift. The yellow arrow points to the top of the swivel bracket. At B, the engine has lifted and the swivel tube is now visible.
Engine lift pic.jpg (112.01 KiB) Viewed 3824 times


After supporting the weight of the engine on the hoist, I removed all the transom bolts. Three of them loosened up smoothly, but the starboard lower bolt head initially felt very tight and then rotated easily as if broken. On removal it was apparent that the bolt had been damaged during installation, probably by tightening it with an impact wrench.

Image
Fig. 5. Broken engine mounting bolt.

The engine came away from the transom easily after I removed the bolts. Thankfully, the rigger had not used some aggressively adhesive sealant like 3M5200 for the installation. It looked like silicone sealant had been used, and not much of that. All the holes in the transom were dry, but the broken bolt was a bit rusty, and the plywood core at that hole showed minor surface deterioration.

Engine mount holes.jpg
Figure 6. Transom after motor removed. Note that the splash well through-hull fitting also has been removed. I had planned to change out all these brass fittings, but after I removed the first one, I could see that the neoprene O-ring was still flexible behind the flare of the tubing and the brass wasn’t corroded, so this fitting was the only one I changed out.
Engine mount holes.jpg (109.79 KiB) Viewed 3824 times


I used the old 4.5-inch transom bolts to perform a test installation of the jack plate. It was apparent that shorter bolts would be required.

Old mounting bolts.jpg
Figure 7. Test installation of the jack plate using the old bolts. It was apparent that I could use 4.5-inch bolts at the top, but something shorter would be needed for the bottom, or I would have to reverse the orientation of the bolts.
Old mounting bolts.jpg (105.19 KiB) Viewed 3824 times


Next step: Wiring the jack plate.
1990 Montauk 17’ w 1991 Mercury 90 HP outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards

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Phil T
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Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby Phil T » Wed Dec 21, 2022 5:31 pm

Presume you already know to set the engine so that the anti-cavitation is 1-1/2 to 2" above the keel at its lowest setting.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

msteinkampf
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Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby msteinkampf » Mon Jan 02, 2023 9:51 pm

Wiring the jack plate

Before doing the actual installation, I did a dry fit of the jack plate to ensure that all the bolt holes lined up and the hydraulic pump worked. The unit comes with a wiring harness that seems of good quality, with all the wires labeled. It only took a few minutes to connect and test the pump. The motor was still in the full-up position when left that way for several days. The only challenge for the wiring was where to mount the two relays. The instructions emphasize the importance of this:

    CAUTION: Select a dry location for the relays and securely mount there.

And that is the problem with installing this unit in a Montauk: no bilge in which to install the relays. I followed the clever approach used by dtmackey on his Whaler 15 project and attached the wiring and relays under the motor cowling as shown in Figure 8.

Jack plate wiring.jpg
Figure 8. Jack plate wiring installed under the engine cowling. Power was tapped from a tilt relay (circle). The jack plate relays were attached to studs holding the low-oil warning module (arrow). All the wires were run through the engine harness retainer (1). In this view a cover has been removed that normally hides much of the engine wiring.
Jack plate wiring.jpg (222.25 KiB) Viewed 3738 times

After removing the cover that protects the powerhead wiring, it wasn’t difficult to find a terminal that was “hot” using a multimeter. I attached the relays to studs that held the oil-warning module at the lower part of the powerhead.

The wiring harness includes a run of about ten feet for mounting the switch to the console, but this wasn’t even close to being long enough for this installation, especially with the relays up under the engine cowling, so I spliced in another six feet of 14-gauge Ancor marine wire. Since these wires were going through the rigging tunnel and I wasn’t sure whether the splices would wind up in the tunnel or in the console, I used adhesive-lined heat-shrink butt splice connectors and covered them with additional pieces of adhesive-lined heat-shrink tubing to minimize the risk of water exposure. If this turns out to be a problem in the future, I’ll locate the splices under the cowling and replace all the wires that lead to the console.

Next step: Bolting the jack plate to the transom.
1990 Montauk 17’ w 1991 Mercury 90 HP outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards

msteinkampf
Posts: 37
Joined: Tue Nov 15, 2022 4:05 pm
Location: Alabama/Louisiana

Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby msteinkampf » Wed Jan 04, 2023 4:05 pm

Bolting the jack plate to the transom: PART 1

Here are the mounting instructions that come with this jack plate:

Mount Atlas Micro™ plate onto the transom using the four mounting bolts that came with the engine… Select the proper mounting hole on your engine according to your situation and mount to Atlas Micro™ using four ½”-13 x 3” stainless steel bolts, flat washers, and lock washers.

This sounds simple enough, but I started by reviewing information about jack plate installation on this and other boating forums, instructions for the installation of jack plates made by other manufacturers, and rigging manuals for Mercury, Yamaha, and Suzuki outboard motors. I searched online for videos about jack plate installation, focusing on videos produced by professional boat riggers and jack plate manufacturers. In the end, I found that almost every information source, even the ones produced by professional riggers or a jack plate manufacturer, had some significant error or omission.

I broke down this process into four steps:
  1. identifying the correct positions for the jack plate and engine
  2. selecting the fasteners and transom reinforcements
  3. applying sealants as needed
  4. orienting and installing the fasteners

1. Identifying correct positions for the jack plate and engine.

I wanted to maximize the amount of contact between the jack plate and the boat transom, but there wasn’t any choice in the matter - if I was going to use the bolt holes already in the transom, the jack plate mounted in only one position, with the top of the jack plate three-eighths of an inch above the top of the transom – close enough for me. I positioned the engine so that the ventilation plate was about one inch above the keel. Although it is commonly recommended that this distance be 1.5 or even two inches (and with a 4-inch setback even a bit higher), I wanted the initial engine height to be lower so that I could optimize its position based on sea conditions. Although positioning the engine was the first step, it’s the one that will be finalized only after a few sea trials.

2. Selecting the fasteners and transom reinforcements

T-H Marine offers the option of purchasing their own jack plate bolt kit, but it was out of stock on their online store. I used bolts that I had on hand for the dry fit so I could be sure to order the right bolts for the final installation. It was clear that reusing the old transom bolts wasn’t going to be an option, since the lower bolts interfered with the jack plate, as shown in Figure 7 above. This might not be such a good idea anyway, since these bolts might have been stretched during the many contacts of the lower unit with sandy bottoms over the past 30 years, or that time when I ran over a pontoon bridge cable. (Note: approach pontoon bridges with extreme caution, especially when they are honking a horn.) After the dry fit, I ordered a 4-inch bolt kit from Bob’s Machine that consists of four 1/2-inch coarse-threaded 300-series stainless steel 4-inch bolts and four 2.5-inch bolts along with stainless steel washers and brass lock nuts. I also ordered two 316-grade 3.5-inch bolts from Bolt Depot. I didn't get this hardware locally as I was uncertain about what kinds of fasteners were typically used for jack plates until I got my order from Bob’s, and Home Depot doesn’t stock brass lock nuts. That isn’t to say that the fasteners at Home Depot are all junk, though. Here’s a photo I took of some stainless steel hex bolts at my last visit there.

Home depot bolts.jpg
Figure 9. Four ½-inch bolts at Home Depot. The one on the upper left is the same grade and from the same manufacturer as what I received from Bob’s Machine.
Home depot bolts.jpg (134.41 KiB) Viewed 3684 times


There is a bewildering array of standards for fasteners: ASTM, ASME, SAE, IFI, and others. If you see a bolt with “F593” on the head, it meets the chemical and mechanical requirements for stainless steel bolts 1/4 inch to 1-1/2 inch set by ASTM International (formerly known as the American Society for Testing and Materials). A “C” after this code means that the bolt is made of 304 stainless steel or a similar alloy with a minimum yield strength of 65 ksi and a tensile strength of 100-150 ksi (more about this later). For the lower transom holes, I plan to use the 316 stainless steel bolts for their superior corrosion resistance. (Their heads were labeled “F593G 316”). I wouldn’t buy a bolt that didn’t have the standard marked on the head. You could make a case that ALL the stainless steel on this project should be 316 grade, but keep in mind that the bolts used to construct the jack plate, the bolts supplied by Bob’s, and the old transom bolts are all 304 stainless steel (or something similar).

By the way, the code “THE” on the bolt heads stands for Tong Hwei Enterprise Co., Ltd, a Taiwanese firm that bills itself as “the leading Stainless Steel Fasteners manufacturer in the world”. Fasteners labeled “THE” were probably made in Taiwan or Thailand.

My old engine mounting bolts were installed with 1.5-inch diameter stainless steel washers on the transom. There is no sign of stress cracking or other fiberglass damage at the splash well, but I decided to use aluminum support plates for the jack plate installation for extra security. Most of the plates I found for sale online are imported, cast aluminum made of an unspecified alloy, but a domestic fabricator (Halk Marine Fabrication & Design, in Covington LA. https://halkmarine.com/) sells a set of 3/8-inch thick CNC-machined marine-grade 5052 aluminum support plates. They also offer deep engraving, and the example on their Web site looks impressive. I thought it would be nice to have a Boston Whaler logo engraved on the top bracket, but I planned to arrange for this locally so that I would get exactly what I wanted. This was my first mistake on this project. Despite several days of online searching and phone calls, I couldn’t find anyone within one hundred miles of where I live who could do this. If you decide to order these plates and want them engraved, I suggest you send them the graphic file, and they will do the engraving at the same time they cut the plate.

Next: Applying sealants and installing the fasteners
1990 Montauk 17’ w 1991 Mercury 90 HP outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards

msteinkampf
Posts: 37
Joined: Tue Nov 15, 2022 4:05 pm
Location: Alabama/Louisiana

Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby msteinkampf » Thu Feb 02, 2023 12:00 pm

Final installation, part 1

The mounting instructions that came with this jack plate were rather nonspecific.
"Using flat washers and lock washers, attach the jack plate to the transom with the bolts that came with the engine ... use four stainless steel ½ inch-13 3-inch bolts to secure the engine to the jack plate."

There was no mention of how tight to secure the bolts or whether sealant is recommended. Searching online, I found a wide range of recommendations for this step. The photo of the jack plate in the Atlas info sheet that accompanied my unit is indicative of this variety, as shown in Figure 10.

Atlas jack plate bolts.jpg
Figure 10. Photo from info sheet that accompanied the Atlas Micro Jacker. Note that one transom mounting bolt has a brass lock nut (arrow); the other mounting bolts have conventional (non-locking) stainless steel nuts with split-ring lock washers. The bolts used to mount the motor to the jack plate appear to be fully threaded (sometimes referred to as “tap bolts”); these have a lower strength than hex head bolts which are only partially threaded.
Atlas jack plate bolts.jpg (113.4 KiB) Viewed 3564 times

I thought it might be prudent to collect more information before proceeding with the final installation; I started by searching the continuousWave.com Web site. I couldn’t find anything regarding bolt torques for jack plate installs, but I did find a discussion thread about engine mounting bolt torque (https://continuouswave.com/forum/viewto ... 890#p29890). The answers there ranged from “Snug. Do not overtighten, just tight” to 50 ft-lbs, with 40 ft-lbs cited from an Evinrude E-TEC manual. Next, I contacted Bob’s Machine Shop since I had bought their bolt kit. Their initial reply was unsatisfying:

For torquing the transom bolts:
"Check with your boat manufacturer for their recommended torque value."

For the bolts connecting the motor to the jack plate:
"Torque the motor to the jack plate using the engine manufacturer’s specified torque spec."

Neither my Boston Whaler owner’s manual, my Mercury outboard owner’s manual, nor my OEM service manual (circa 1989) had any engine mounting bolt torque specifications nor any mention of jack plates. I was unable to find any pertinent specifications online from Boston Whaler, but I did find some potentially useful info from several outboard engine manufacturers.

Suzuki outboard rigging manual 2018 (https://outboarddirect.com/wp-content/u ... igging.pdf)
“MOUNTING TO THE TRANSOM. For DF40A/50A/60A, DF70A/80A/90A, DF100A/115A/140A motors, use M12/155 bolts and lock nuts [type not specified], with torque of 40 lb-ft. For DF 150-350 engines, 1/2”-20UNF bolts and Nylon lock nuts are used, with torque of 58.0 lb-ft).”
(Six bolts are used for the larger engines.)
“Never reuse the lock nut after it has been threaded into position and torqued. Once you have tightened the lock nut, it will no longer have the necessary fastening performance if you reuse it. NOTE: To reduce possibility of thread damage to mounting bolts and possible incorrect torque, do not use an impact wrench. Apply sealant to shanks of the bolts, not the threads.”

Yamaha 2012 Outboard Rigging Guide, Worldwide Edition (https://gfretwell.com/ftp/Rigging%20guide%202012.pdf)
"Use M10 bolts torqued to 31 ft-lbs. For above 115 (V4) and F75 use M12 bolts torqued to 38 ft-lbs. Double nut to lock (tighten inner nut first). *Tighten the mounting bolts/ nuts by suitable torque due to boat transom structure, material, design, etc."

Mercury 2016 Operation, Maintenance, and Installation Manual for 75/80/90/100/115 Pro XS Four Stroke (https://issuu.com/glsense/docs/mercury_ ... n__mainten)
“Mercury Marine provides validated fasteners and installation instructions, including torque specifications, with all of our outboards so they can be properly secured to boat transoms.”

The Mercury manual calls for 1/2”-20 bolts with nylon lock nuts and flat washers; torque transom bolts to 55 ft-lbs, torque bolts for metal lift plates and setback brackets to 90 ft-lbs. Mercury advises against using an impact wrench when mounting engine. The Mercury manual even shows a decal with this information on the side of the engine, as shown in Figure 11.

Mercury torque spec decal.jpg
Figure 11.
Mercury torque spec decal.jpg (50.86 KiB) Viewed 3564 times

Note that Yamaha uses stainless steel double nuts with 10 mm diameter bolts for smaller motors and 12 mm bolts for larger engines, while Suzuki uses single-use locknuts with 12 mm bolts for smaller engines and ½ inch bolts for larger motors. Mercury claims to supply ½ inch fine-thread bolts and (reusable) nylon lock nuts. For the similarly sized 12 mm and ½ inch bolts, the torques specified by the engine manufacturers ranges from 38 to 58 ft-lbs for transom bolts; for attachment of the engine to a jack plate, Mercury specifies 90 ft-lbs, a number which by my calculations could result in a load on the bolt that exceeds its yield strength (more on this later).

Armed with this information, I visited a local boat show and two boat dealers in the area. I was most interested in the hardware and rigging techniques for Mercury outboards, since they are the only engine company that specifies how to attach a jack plate. I talked with boat manufacturer representatives and dealers (at the boat show) and service department personnel (at the dealers), and I looked over more than thirty outboard engines mounted to boats. The Boston Whaler dealer at the boat show was kind enough to phone his service manager for more information while I was visiting. This is what I learned:

- Virtually every Mercury engine was mounted using ASTM F593C (304 stainless steel) fine-thread bolts supplied by the Taiwanese firm THE, with one exception – the Boston Whaler boats (see Figure 12). Whether the bolts currently used by BW are better or worse than the Taiwanese bolts is debatable. You can download a whitepaper from the Industrial Fasteners Institute that discusses this concern by going to this link (https://www.indfast.org/info/free-technical-info.asp) and clicking on the tab marked "Stainless - 304 vs F593". I found only one boat (with a Mercury outboard) in a dealer’s yard that had 316 stainless steel bolts. All the Mercury bolts had brass nylon lock nuts. The Yamaha engines all had metric bolts and doubled stainless steel nuts. I didn't encounter any Suzuki engines.

BW transom bolt.jpg
Figure 12. Engine mounting bolt on a 2023 Boston Whaler Montauk 21. The code on the bolt head indicates it was manufactured by the Fall River Manufacturing Company of Fall River, Massachusetts, is made of 304 stainless steel, but does not necessarily meet ASTM specifications for this type of fastener.
BW transom bolt.jpg (85.14 KiB) Viewed 3564 times

- I didn't find any dealers who used a torque wrench for tightening engine mount bolts. None of the service department personnel I talked with were familiar with the torque specs for engine mounting bolts, even though these are listed on the side of the Mercury outboards. I did encounter a boat manufacturer’s representative at the boat show who had some familiarity with the torque specs.

- Impact drivers are routinely used for transom and jack plate installation by dealers.

- NONE of the boats I examined had conventional nuts with split lock washers on the bolts used to attach the engines to transoms or jack plates.

- The dealers I spoke with use 3M Marine Adhesive Sealant 5200 for sealing the transom bolt holes (more on this later).

This post is getting a bit long, so I am going to stop here for now.

Next: Final installation, part 2
1990 Montauk 17’ w 1991 Mercury 90 HP outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards

msteinkampf
Posts: 37
Joined: Tue Nov 15, 2022 4:05 pm
Location: Alabama/Louisiana

Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby msteinkampf » Sun Mar 12, 2023 10:25 am

Here’s a challenge. Watch this video about jack plate installation and see how many deficiencies you can find in their installation process. (My answer is at the end of this post.)

https://www.youtube.com/watch?v=CJc3LFIYRcI&t=1443s&ab_channel=BobsMachine

I must admit to having fallen down a rabbit hole regarding the tightening of these bolts. I found that one of the best sources for publicly available information about bolt tightening is the National Aeronautical and Space Administration (NASA), who apparently has hired engineers that sit around all day thinking about the best way to tighten bolts. This is probably money well-spent, since NASA has had some painful experiences involving fasteners. For example, a science experiment on the space shuttle Atlantis that cost $128 million to set up was ruined by an improperly installed ¼ inch bolt (see here for the story: https://www.nytimes.com/1992/08/29/us/tiny-bolt-blamed-in-shuttle-failure.html#:~:text=A%20tiny%20bolt%20apparently%20caused,the%20space%20agency%20said%20today. NASA sent the experiment up again on a later space shuttle, and it failed due to corrosion of a cable. I guess those NASA engineers hadn’t thought about the effects of salty Florida air.) And there is the sad story of the space shuttle flight that was delayed because a titanium nut on the hatch door handle stripped. A maintenance man called to fix it was delayed because of security problems and a dead battery on one his tools, and he had to use a hack saw to cut off the nut (story here: https://www.newspapers.com/clip/27296929/broken-door-handle-delays-challenger/). By then, it was getting late in the day, so the flight was postponed to the next day (at a cost of about $1.2 million). Unfortunately, a cold front blew through overnight, some rubber O-rings on the rocket got too stiff, and ... you probably know the rest of the story about the Challenger flight. Much of what is discussed below came from NASA’s Fastener Design Manual, publication 1228, published in 1990 (available here: https://mae.ufl.edu/designlab/Lab%20Assignments/Fastener%20Design%20Manual%20(NASA).pdf).

I think that part of the reason for the range of torque values recommended for outboard motor and jack plate bolts is because the bolt is part of a fastener system comprising the bolt, nut, washers, and the objects being fastened. The force that a fastener system uses to secure two objects is obtained by stretching the bolt shaft (this force is termed the axial tension or tightening force). Bolts are elastic, but if the axial tension is excessive, the bolt loses its elasticity and becomes permanently stretched; if tightening continues, the bolt will break. It’s worthwhile to review some definitions about bolt tightening.

Ultimate tensile strength – the maximum force a fastener can maintain before fracture.
Yield strength – The axial tension at which a bolt loses its elasticity and becomes permanently stretched.
Proof load – The maximal axial tension at which the bolt maintains its elasticity. This is typically 85-90% of the yield strength.
Typical clamp load – The axial tension recommended for a fastener. This is usually about 50%-75% of the proof load. This number is generally conservative, in part because of the uncertainty of determining axial tension from a torque value. Torque wrench accuracy can be as low as +/- 25%; NASA requires that all torque wrenches be calibrated on initial use, every 30 days, or whenever the wrench is dropped on the floor!

Here is a graph that illustrates these terms:
Bolt tightening graph.jpg
Relationship between axial tension and strain on a bolt.
Bolt tightening graph.jpg (32.9 KiB) Viewed 3103 times


Source: SmartBolts. Fundamentals of Basic Bolting. http://www.smartbolts.com/fundamentals/#:~:text=Proof%20load%20is%20defined%20as,95%25%20of%20the%20yield%20strength.

Unfortunately, the axial tension on a bolt cannot be easily measured, so we are left with determining the force required to turn a nut on the bolt. This is the torque value, and only about 10% of the torque is due to the axial tension on the bolt; the rest is due to friction in the fastener system. The axial tension can be estimated from the bolt torque using some standard engineering formulas you can review here:

https://www.engineeringtoolbox.com/bolt-torque-load-calculator-d_2065.html

A given torque on a bolt will yield different axial tensions depending on the bolt material, the thread design, the design of the nut and washer, whether the bolt threads are lubricated, and even whether it is the bolt head or the nut is being turned. Bolt torque charts usually list values for dry bolts with the nut being turned, but some charts include alternate (and often much lower) recommended torques for lubricated bolts. Basically, if you lubricate a bolt before tightening it but you use the same torque specified for a dry bolt, you risk damaging the fastener.

Here are a few other things I learned from reviewing the NASA manual:

- Most locknuts (including Nyloc nuts) don’t really help maintain bolt tension; they are loss retention devices that keep the nut from falling off the bolt.
- Split ring lock washers are essentially worthless for maintaining bolt tension. (Yes, I was surprised, too. Watch this video: https://www.boltscience.com/pages/helicalspringwashers.htm)
- For multiple fasteners, the bolts should be tightened sequentially in a crisscross pattern.
- There should be two threads protruding past the end of the nut.
- Bolts should be re-torqued after installation to account for relaxation of the fastener system.
- NASA recommends against using jam nuts because it is difficult to obtain reliable torque values for the fasteners. They do lock the nuts in place effectively, though, which is probably why Yamaha recommends them.

The charts I pulled up online indicated that the appropriate torque for the bolts I had received from Bob’s Machine was about 55 ft-lbs (with dry threads), but I wasn’t quite ready to give up on finding out why Mercury had such a high torque (90 ft-lbs) when this type of bolt was used to mount the engine to a jack plate. I found a Mercury online customer service information site that lets you send them a message if you enter your Mercury outboard serial number, so I sent them this:

Sent to Mercury Marine online on 1/31/2023 (https://www.mercurymarine.com/en/us/contact/outboard-customer-assistance)

I am installing an Atlas Micro Jacker hydraulic jack plate on my 1991 Mercury 90 HP outboard engine. My OEM service manual (circa 1989) does not specify bolt torques for this installation, but the latest version of the Mercury Operation, Maintenance, and Installation Manual I could review online (2016 version) gives recommended torques of 55 ft-lbs for the transom bolts and 90 ft-lbs for the bolts attaching the engine to the jack plate, using “validated fasteners provided by Mercury”. My local Mercury dealers use ½”-20 F593C bolts (304 stainless steel bolts with brass lock nuts) supplied by THE for this type of installation, and they do not bother to use a torque wrench. Typical torque specifications for this bolt are in the range of 40-55 ft-lbs, and my calculations (using a yield strength of 65,000 psi and stress area of 0.1599 sq.in.) indicate that a torque of 90 ft-lbs will exceed the load at yield strength of this bolt. (load at yield strength=yield strength x bolt stress area = 65,000 psi x 0.1599 sq.in.=10,393.5 lbs. Torque at yield strength load: T=KdF, 0.2 x 0.5in. x 10,393.5 lbs./12 = 86.6 ft lbs. My question is: Is your torque specification for jack plate attachment (90 ft-lbs) for a different type of bolt, or is this an error on your part, or on mine?

I got this reply a week later (the typos are theirs):

We are very sorry, as there is not documentation on what the tourque specs should be while using a jack plate. We have looked in installation manuals, as well as service manuals. Mercruy Marien can only suggest at this point you work with the manufacture that made the jake plate you are using to see if they have any instite on what tourque value will work for your application.
We hope this information is helpful to you. Should you have any further questions or concerns, please contact our Customer Service department at 920-929-5040 between the hours of 7:30 am and 4:30 pm, Monday through Friday, CST.
Sincerely,
Mercury Outboard Customer Assistance
Ref: 2023-00011638


Finally, I sent another message to Bob’s Machine saying that neither my boat manufacturer nor my engine manufacturer would supply torque values for this installation. I immediately got a reply: 55 ft-lbs. And that was the number I used.

Finally, there is the question of what kind of sealant to use. Personally, I think 3M 5200 is a poor choice for this installation. What if the unit breaks, or performance deteriorates and I want to remove the jack plate? I can’t see the logic of using an adhesive that will damage on removal the objects you are bonding unless you are confident that you will never have to remove the equipment. I went with Loctite PL Marine Fast Cure Adhesive Sealant, which is equivalent to 3M Marine Adhesive Sealant 4000 UV and is available at my local Lowe’s. I applied the Loctite on the plate as well as around the bolt holes to minimize any vibration between the transom and jack plate, which will reduce the chance of fasteners loosening over time. Here is a photo of the final installation.

jackPlateInstall.jpg
Final installation of jack plate on my Montauk 17
jackPlateInstall.jpg (148.91 KiB) Viewed 2390 times


My 3½ inch bolts turned out to be a little short, but the threads do engage the nylon ring of the locknut, so I’m going to leave them as is for now. Torquing to 55 ft-lbs seemed quite snug, but there was no cracking of the fiberglass on the transom. I couldn’t get the socket of my torque wrench around the nut on the lower transom bolts, so I was forced to torque those fasteners by turning the bolt heads.

Next step: Testing the unit on the water.

Bob’s Machine video deficiencies:
- Using a sealant that will pull off the gelcoat if the jack plate is ever removed (although this sealant is commonly used for mounting jack plates).
- Sealant is on bolt threads, not wiped off before nut installed.
- Nuts used do not appear to be self-locking.
- Impact wrench used to tighten nuts.
- No torque wrench used (and this deficiency is acknowledged in the video).
- Fasteners are not cross tightened.
- No follow-up re-torquing after installation
1990 Montauk 17’ w 1991 Mercury 90 HP outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards

msteinkampf
Posts: 37
Joined: Tue Nov 15, 2022 4:05 pm
Location: Alabama/Louisiana

Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby msteinkampf » Wed May 17, 2023 8:06 am

I tested the [Atlas Micro Jacker hydraulic jack plate on my MONTAUK 17 with 1991 Mercury 90-HP three-cylinder two-stroke-power-cycle engine] on the water in early May 2023.

Performance with the jack plate all the way down was about the same as before the installation. The time to plane less than three seconds, with a boat speed of 29-MPH at engine speed of 4,000 RPM, my cruising engine speed.

When I raised up the jack plate about two inches from lowest position, the boat speed jumped to 31-MPH and the engine speed increased to 4,200-RPM. Raising the jack plate to maximum lift, the boat speed remained at 31-MPH, but the propeller began to ventilate with even the most gentle turn.

As seen in Figure 15, the distance from the bottom of the engine gear case skeg to the hull keel with the jack plate all the way up was about 11-inches.

With [the hull itself only having] a draft of about 10-inches, I could potentially idle in water less than two feet deep even without trimming up the outboard engine. I could raise the engine another 1.5-inches by installing it higher on the jack plate, but I won’t decide about that until after my next fishing trip.

Atlas jack plate 5-10-23 copy 3.jpg
Figure 15. With the jack plate all the way up, the bottom of the skeg is about 11-inches below the keel, and the anti-ventilation plate is 5-inches above the keel.
Atlas jack plate 5-10-23 copy 3.jpg (135.78 KiB) Viewed 2920 times


After the trial run, I re-tightened all the engine and jack plate mounting bolts to 55-lbs-feet torque. It took about half a turn on the transom bolts and a quarter turn on the bolts attaching the engine to the jack plate.

This project is now completed!
1990 Montauk 17’ w 1991 Mercury 90 HP outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards

jimh
Posts: 11672
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby jimh » Wed May 17, 2023 11:36 am

Perhaps you can also collect and publish some more performance data with the engine throttle at full.

Also, mention the propeller in use for these tests, giving the brand, the model, the pitch, number of blades, and diameter.

msteinkampf
Posts: 37
Joined: Tue Nov 15, 2022 4:05 pm
Location: Alabama/Louisiana

Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby msteinkampf » Wed May 17, 2023 12:16 pm

Thanks for your interest. As you can see from the previous photos, I'm using a 3-blade stainless prop. The diameter is 13 inches, and here is the model and pitch info:
BW prop.jpg
Figure 16. The propeller currently in use on my 1991 Mercury 90 HP outboard, an older QUICKSILVER QSS three-blade 19-pitch.
BW prop.jpg (126.09 KiB) Viewed 2893 times


I would be happy to provide you with the performance data you requested as soon as I am able to return the boat to the lake where the initial trials were performed.
1990 Montauk 17’ w 1991 Mercury 90 HP outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards

msteinkampf
Posts: 37
Joined: Tue Nov 15, 2022 4:05 pm
Location: Alabama/Louisiana

Re: Atlas Micro Jacker hydraulic jack plate on a Montauk 17

Postby msteinkampf » Thu Aug 10, 2023 3:05 pm

After finishing the jack plate installation, I spent five days in Louisiana fishing. It seemed like raising the engine so that the ventilation plate was 3-inches-above-the-keel was optimal for performance in a moderate chop, but where the device really excelled was in shallow water. We were once blown by the wind into water about a foot deep at the bank of a bayou, and by raising the motor all the way up and applying a little trim out, we easily got back into deeper water. After returning to Alabama, I spent some time evaluating the effect of the jack plate on boat performance. Here are some numbers I obtained before and after the jack plate installation:

    Average of two runs in opposite directions
    Engine at full-throttle
    Anti-ventilation plate position above boat keel is the variable

    A-V Plate ENGINE BOAT SPEED
    INCHES RPM MPH
    1.125* 5400 39 *no jack plate
    1.5 5300 39
    3.0 5400 40
    4.0 5550 40
    6.0 5600 40

As you can see, the performance gain at WOT with the jack plate was minimal, but my impression about the optimal motor position was confirmed on careful testing: three-inches above the keel.

The pre-jack plate and post-jack plate installation figures aren’t completely comparable, since the numbers were obtained nine months apart, and the temperature was about ten degrees higher for the second test.

Nevertheless, I am glad to have installed this jack plate, and I would encourage other Montauk owners who operate in shallow water to consider installing one.
1990 Montauk 17’ w 1991 Mercury 90 HP outboard
1995 Aquasport Explorer 245 w twin 1995 Yamaha 150 HP outboards