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Thread: Mild hop-up of a Merc 350 . . .

  1. #11
    Team Member bobvdinghyracer's Avatar
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Size:  228.9 KBName:  35 twin  mk20 leg shortened 4 in with custom quickie 16 21.jpg
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  2. #12
    Team Member bobvdinghyracer's Avatar
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    pics above showing in my hand is what i use for adapters readily avaible apx 10 bucks machine to fit your prop , a pic og 35 twin on a short mk 20 leg with custom built kgfoot highly modded other pic is cut down mk30 pan , shaft adapter using an old 20cube crank bottom and a upper part of a 4 cyl drv shaft mated together the other 2 pieces were needed dor the newer twin with more cubes and newer rear bolt pattern not needed for early 35.... this ran high 40`s on a hard bottom zodiac dinghy , this yr gonna throw it on my halkelly fooling to see what she can really do .... lake racer ... this all can be built pretty cheaply , fun and fast btw the prior 1 i built above, all pretty is fully dressed with stock 35 hp cowlings and merc 200 decals ha ha runs sweet and weighs apx 85-90 lbs (full gearshift)

  3. #13
    Team Member smittythewelder's Avatar
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    WOW, what a response!! Rumley, Dinghy Bob, thanks so much, what fun projects!! Shows you really can "make a silk purse from a sow's ear" sometimes. I have to study those photos, there's a lot to see there. Thanks again!

  4. #14
    Team Member bobvdinghyracer's Avatar
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    forgot to mention , yes she will take some exhaust porting with a smile ... and ya i did ... even better is the newer version ... little heavier .. more cubes apx 33 cube and the newer style pistons , some porting use the power ported pistons from a triple ... litle more grinding on the ports and .... , if your daring build some reed blocks and add 2 carbs instead of 1 .... should be interesting ... i did 1 but was stock on the mk 20 leg stock g box stock height .... had a lot of balls ... thats what those other plates were for in above pics ... the boat i had at time didnt handle well and project was shelved for the time but am gonna do another with above mods .... why ? cause i can .... picture the 650/700 x race motor merc built and could be same idea just 1 less cyl. should make some serious power for an old anchor ... and CHEAP FUN

  5. #15
    Team Member OldRJexSea's Avatar
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    Default Short tech comment.

    Smitty, I took a look at your Tech post as you suggested. I suppose that folks enjoying themselves by hot rodding those old motors in modern times is a good enough outlet for desires to apply their creative energies in assembling usable gear at modest cost.

    I am ambivalent about such efforts mostly because I am too bleeping old which is compounded by no lifetime left to build a truly modern outboard racing motor. A small class size 2-stroke using external intake pumping, hydrodynamic bearings, (or recirculating oil mist for mod. roller bearing motors), and electronic FI & ignition; all the proper items needed to have a motor which minimizes the current pollution of air & water by outboard motors and is much more efficient at producing power. (And running on standard pump E85 ethanol (or E96) for even less pollution). (As you know, my last effort on a standard 2-stroke design was 1972, no time then either).

    I remain truly curious as to why major motorcycle manufacturers developed such a fine set of 2-stroke machines until the 1990’s but did not change to the above mechanical methods when the EPA set exhaust emissions standards that could not be met with lubricating oil included in motor fuel.

    The Moto-GP racing which eventually set 4-stroke displacement at almost twice the allowed 2-stroke motor size was probably tied partly to certain motorcycle manufacturers wanting into the game using their newer 4-stroke high performance Street motors plus the looming emission standards in the major markets. The GP racing drove prestige & sales for the major manufactures so they took the costly path of total redesign to 4-stroke for their machines after the GP dominance of 2-strokes was ended by the size limitations. Much easier to add systems than total redesign but maybe not given Accounting Dept. projections.

    Bottom line, in my estimation, for folks with a bunch of energy left to fiddle with old 2-stroke outboards would be to develop and add the systems listed above to prove that truly clean, efficient, high power density, 2-stroke motors requires a different mindset but is worth the effort.
    Somebody can do it !! Might be more fun too.

    RR

  6. #16
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    Dingy Bob made me the driveshaft adapter used with the dual carb, external reeds motor on page one. He does nice work!

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

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