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Fodder for the Buzzards:
What constitutes an acceptable motor mount rating for a raft or cataraft.
The N brand retailer refuses to answer my querie and removes my questions from the Q&A forum on their site. Note: A HP is 33000 ft lbs work/min.
Minions: step in here:
 

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Fodder for the Buzzards:
What constitutes an acceptable motor mount rating for a raft or cataraft.
The N brand retailer refuses to answer my querie and removes my questions from the Q&A forum on their site. Note: A HP is 33000 ft lbs work/min.
Minions: step in here:
huh?
 

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I don't know the answer, but it is on here somewhere. Check these threads.

Link Here > Click
 

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Hi,

Most of the "jackass" type mounts are rated in pounds -- that is, the straight weight of the motor. I don't know that I've seen any mounts (that type or otherwise) that are rated for torque or other characteristics.

If you had a specific motor and mount type that you were considering and would share here, there may be folks here who have used it, and could chime in.

FWIW.

Rich Phillips
 

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When any mount is relying on adhesive D-rings for retention, it would be impossible to provide any reliable measure of capacity. Any rating you might find is essentially useless. This falls squarely under the "don't be a moron" ratings system. Follow that.

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Amending

Hi,

Most of the "jackass" type mounts are rated in pounds -- that is, the straight weight of the motor. I don't know that I've seen any mounts (that type or otherwise) that are rated for torque or other characteristics.

If you had a specific motor and mount type that you were considering and would share here, there may be folks here who have used it, and could chime in.

FWIW.

Rich Phillips
Actually, the jackasses can also be categorized by horsepower limits. I find that sort of unuseful, since a 25 hp four stroke weighs a lot more than a 25 hp two stroke. And the torque characteristics of the two are quite different.

Hard data.

I have run a 25 two stroke hp motor clamped directly to a stock NRS cat yoke on a 16' boat. I have run the Grand repeatedly with an 18 hp four stroke - much heavier - on a jackass on a modified NRS cat yoke on a 20' Jacks El Tigre Grande.

FWIW.

Rich Phillips
 

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Actually, the jackasses can also be categorized by horsepower limits. I find that sort of unuseful, since a 25 hp four stroke weighs a lot more than a 25 hp two stroke. And the torque characteristics of the two are quite different.

Hard data.

I have run a 25 two stroke hp motor clamped directly to a stock NRS cat yoke on a 16' boat. I have run the Grand repeatedly with an 18 hp four stroke - much heavier - on a jackass on a modified NRS cat yoke on a 20' Jacks El Tigre Grande.

FWIW.

Rich Phillips
Hey Rich. I just looked at my mount and it says 2 stroke only on it.....go figure.
 

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Hi Dan,

I don't have hard numbers, but I'll bet my Tohatsu 18 four stroke weighs almost twice as much as that old 25 hp Mercury I was running on the NRS cat.

A jackass increases the leverage on the frame portion of the mount. So I reinforced the rear end of the frame on my big rig to be sure bouncing around in rapids didn't pull the whole yoke right off the longitudinal frame tubes.

Rich
 

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Hi Rich,
I have a 5 hp 4 stroke Honda that weighs 7 lbs more than my 8 hp 2 stroke Johnson. Pushing a flotilla of 6 rafts, you don't notice a big difference between the two motors. Pushing my speed boat, the difference is 2.2 mph compared to 4.8 mph. The Honda stays at home more times than not.

The jackass on the back of my speed boat seems flimsy to me. I keep the motor in the boat until needed. The mounts for my cat and raft are solid pipe and plywood with long shaft motors. FWIW. I'm not a big fan of jackasses, but they have their uses and sometimes the only way to get your motor high enough out or low enough in the water

What was the original question again?
 

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Hey Rich. I just looked at my mount and it says 2 stroke only on it.....go figure.
This is new to me. Why would a mount be rated for only 2 or 4 stroke? I understand that 2 strokes have more horse power for the weight but they could still rate them for overall weight / HP. Maybe even a ratio. ??
 

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This is new to me. Why would a mount be rated for only 2 or 4 stroke? I understand that 2 strokes have more horse power for the weight but they could still rate them for overall weight / HP. Maybe even a ratio. ??
Probably because some jackwagon threw a 100lb 4stroke 10 horse kicker on a jack that was built (and labeled) around the lighter 2 stroke version. They also probably sued, and won, when their nice new kicker snapped the jack and went plummeting in the depths...the lawyers evidence... the thing was labeled "up to 10 hp". And as the Coast Guard classifies things by HP (not thrust, weight or other potentially useful criteria) the HP standard stuck for kicker mounts, jacks and the like. This of course is speculative but it's my guess.
 

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Discussion Starter #15
A HP is a measure of work and defined as roughly 33000 ft lbf /minute or (550 ft lbf/sec). Embedded in that rating (for the motor mount), I hope is some factor of safety as well as the ability to contain the motor in an event. Mass of the motor, # of drings etc would be important in an event but not part of the problem stated. Length of the shaft would be important since it produces a torque or moment about the boat. To date the only safe mount I've ever viewed was a mid raft engine mount affixed mid raft on a 3 dimensional space truss.
What I view in the market (web) are piles of sh_it promoted by here say as well as eyewitness account of folks that don't have a clue. Embedded in this site are several folks that can offer better.....or should I say safer
 

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Hi "Gary",

If you're looking for a real-world answer, help us out a bit. (Perhaps you were about to do that, but it seems your last post may have been truncated.)

What specific kind of raft/cat are you talking about? What kind of motor? Are you talking about a direct frame mount, a strap-on tube mount, or a "jackass" device?

If you explained your situation a little more simply, there are lots of folks here who could give you additional first-hand input, beyond what's been posted already. And then you can blend that information in with whatever other knowledge you have, in order to make the best decisions about your rig.

FWIW.

Rich Phillips
 

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What is Herbal leaf and were can we get some??

What is a 3 dimensional space truss?? Does NASA sell them? Is that the N brand retailer your complaining about?
 

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Probably because some jackwagon threw a 100lb 4stroke 10 horse kicker on a jack that was built (and labeled) around the lighter 2 stroke version. They also probably sued, and won, when their nice new kicker snapped the jack and went plummeting in the depths...the lawyers evidence... the thing was labeled "up to 10 hp". And as the Coast Guard classifies things by HP (not thrust, weight or other potentially useful criteria) the HP standard stuck for kicker mounts, jacks and the like. This of course is speculative but it's my guess.
elkhaven......I bet you nailed it on the head with your answer. ;)
 

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What is going on here? Are you trying to pull a water skier? I cannot imagine that there is "acceptable criteria" published for a cobbled on motor mount to an inflatable craft. What kind of hp are you looking to hook on to your rig?
 

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Discussion Starter #20
I did a little research yesterday morning and realized this is a can of worms. However, the best answers available is that a 10 hp outboard produces somewhere between 250 and 450 lbs of thrust near the power band. Embedded in that argument are the efficiencies of the motor and the efficiencies of the transmission of mechanical energy, i.e the concept of slip. Prop efficiencies are usually somewhere south of 55%.
That being said, the envelope of: 250 lb x 24in is a torque of 6000 in lbs;
upper end 10800 in-lbs. There are respectable numbers. Combine them with the dead load of the motor, accelerations of the boat, and a respectable factor of safety and what is out there don't begin to do the job.
It's not cat frames I worry about. It's the application of a motor to a raft on a set of arms that when inverted chews up the occupants out of ignorance. Perhaps the afore-referenced jack plate solves the issue.
A quick search on the web only yields a motor mount capable of handling a 1/3 hp electric motor safely....which in itself is a subjective....
 
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