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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 05-17-2012
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outboard mounts

I am buying a new outboard, 4 stroke, to replace my older 2 stroke motor. They weigh about the same, within 5 pounds or so, but in looking through catalogs and such, many outboards are listed as being for two strokes or four strokes.
My current mount is older and while I don't know the brand or model it certainly resembles the design of current two stroke mounts,
But what is the difference between two and four stroke outboards that would suggest a different mount? Is there an inherent difference in the way they shake, or torque?
What's marketed as four stroke mounts certainly look to be more beefed up mounts.
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Old 05-17-2012
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Re: outboard mounts

If it can handle the weight, I don't see why it wouldn't work.
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Old 05-17-2012
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Re: outboard mounts

The difference is weight. Generally, 4-strokes are much heavier. However there are exceptions, such as my 2hp Honda 4-stroke, which is very lightweight and is no problem for my stern rail outboard mount.
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outboard mounts

That eases the mind some I really was not relishing the idea of drilling more holes in my transom if a new mounts holes didn't line up
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Old 05-17-2012
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Re: outboard mounts

I think it is more than the weight of the engine; according to the manufacturers, four stroke engines deliver more torque (especially at low rpms) than their two stroke cousins, and the mount has to be robust enough to deal with it. I have never been able to get a straight answer either on line or in person as to how exactly to calculate if a "two stroke" mount that can handle a 100lb engine is robust enough to handle a four stroke engine that weighs only 70 lbs.

Benajah, I share your concern with the drilling necessary to accomodate a four stroke mounting bracket; that's why when I repowered several years ago, I went with a new two stroke instead of a four. Unfortunately, you don't have that option any more as the industry abandoned small two strokes several years ago. I really think its more than the engine's weight you have to deal with; maybe a talk with the good folks at Garelick (or another manufacturer of mounts) could shed some light on this for you.

Good luck.
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Old 05-17-2012
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outboard mounts

Yeah it's hard to get a straight answer on it. To further confuse things I have seen some mounts advertised along the lines of "for a 15 hp 2 stroke or 10 hp 4 stroke.
Then again, the smallest mount I have seen is for a 12 hp motor which is probably what my mount is made for, and I have a tiny 22 foot boat with what will be a 6 hp motor replacing a 5 hp.
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Re: outboard mounts

I can't imagine there would be enough difference in torque between two similar powered OBs that it would change what mount you need. I would imagine that there are other forces that would be much greater, like lowering the OB too fast, side forces from waves or piers, etc. The weight of the motor does effect how difficult the motor is to raise and lower. I bought a OB motor mount designed for a larger motor on ebay and found that even with the heavy aircooled 4 stroke I had to push pretty hard to lower the motor. Sold that, and got a lighter one that was a breeze to raise and lower.
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Re: outboard mounts

I just did a quick search at West Marine, and that bracket you mentioned rated as "10 hp four stroke/15 hp two stroke" looks exactly like the bracket I bought 10 years ago for my two stroke:

WEST MARINE Outboard Motor Bracket, Aluminum 10hp. (4-stroke); 15hp. (2-stroke) 85lb. 11" at West Marine

If you have a small Oday (I have a 23), this bracket will fit your OEM mounting block and transom holes. Go for it!
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Old 05-17-2012
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outboard mounts

This appears a lot like my current mount, but no mines not an Oday it's a Westerly 22 Cirrus something of an unusual boat in the US.
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Old 05-18-2012
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Re: outboard mounts

It is about the weight as some of the BIGGER motors in the 10- to 15 HP range with electric start and tilt/trim are GIANT compared to the old 2s units
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