O/B motors 2 stroke vs. 4 cycle - Page 2 - SailNet Community
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post #11 of 23 Old 09-09-2006
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Just a quick note. All small Mercury outboards (25hp or less) are made by Tohatsu. The only differance is the decals, you will notice Tohatsu's are now painted Mercury black, and of course the price, Mercury's are about $200-$400 more.
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post #12 of 23 Old 09-09-2006
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Quote:
Originally Posted by Nathan West
Just a quick note. All small Mercury outboards (25hp or less) are made by Tohatsu. The only differance is the decals, you will notice Tohatsu's are now painted Mercury black, and of course the price, Mercury's are about $200-$400 more.
Great! Then I should be able to an impellar for my water pump from a Mecrucy parts catalog?
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post #13 of 23 Old 09-09-2006
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Sorry Shack, I should qualify -don't you hate when they do that- I know that all the small Merc 4 stroke start about 2000 were made made by Tohatsu. The 2 strokes I'm unsure about. also models before 2000 I don't know about I'll try to get more info
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post #14 of 23 Old 09-09-2006
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If you check out Yamaha's site you will notice that only the four stroke is available in long shaft. The weight difference is 25% or 79lbs for the two stroke vs. 99lbs for the four stroke. The other interesting difference is that the alternator on the four stroke outputs 10a vs. the two's 6a. As to why a four stroke weighs more, one good clue is that the displacement of a four (9.9) is 19.7ci while the two (same hp) is 15.0ci.
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post #15 of 23 Old 09-10-2006
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Nathan,
If you have any sources, I am all ears.

But I'm still on course to update/upgrade my o/b to more a contemporary model that is more maint friendly (i.e. resources).

You know - I'd love for a o/b repairman to chime in and tell what the part compatability is between the two for 2007 models. If the sticker on the outside is the whole difference, then its an easy decision.

But I suspect the marketing guys got their fingers in the stew and ensured that there was the odd sized codder pin or a bolt that only produced in northeast Thailand that makes up the difference between the two.


Last edited by Shack; 09-10-2006 at 01:03 PM.
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post #16 of 23 Old 09-10-2006
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having just rebuilt my first two-stroke outboard I gotta say I am not sure why anyone would declare a 2 stroke "on its last legs". (unless you just need a good reason to buy a new motor). 2 strokes are simple, and as long as the reason one isnt running isnt because someone ran it without oil and ruined it totally, everything on it is pretty much easy to replace. No valve train, cam, etc. Four strokes are definitely quieter, and more efficient in terms of miles per gallon. Way more complex and costly to fix, a lot more parts. Less horsepower for the displacement. heavier. Takes more moving parts to operate them valves. 2 strokes just have about three moving parts, pistons, rods, and crankshaft. Reed valves last forever and are easy to replace. No crankcase oil to deal with. I still like the 2 strokes. simplicity is important.
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post #17 of 23 Old 09-10-2006 Thread Starter
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as this motor was with the boat when it was brought i can not confirmed or deny any abuse to the engine the motor part you are correct it is the cheapest item to rebuild but the upper and lower part of the engine are the more expensive items to repair and replace the transmission needs alot of attention the lower housing is cracked and the zincs have been gone for a long time the mounting bracket is broken so the engine will not lock down that assembly is roughly 400 bucks alone the motor is a 1976 model so parts available is also a issue the mechinic and i spent about an hour on the internet before we found about 35% of the parts needed and as he said the parts issue is only going to get worse as time goes on... the engine parts and rebuild is roughly about 450 bucks as the starter and flywheel will need to be replaced the starter is kaput and the flywheel is missing teeth and eroded badly the pump we have assumed also needs to be replaced as well as low water flow from the pump (we were be both impressed that the engine would even run) no amps from alt. so it may have to be rebuilt...
so considering everything i believe that a replacement engine would be better in order than repairing this one but maybe i am wrong
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post #18 of 23 Old 09-10-2006
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Catalyst27-

I would definitely upgrade to a new OB motor if I were in your shoes. Investing more in the old one is probably throwing good money after bad.

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post #19 of 23 Old 09-10-2006 Thread Starter
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yes sir my thoughts also Thanks to all of those who gave an opinion
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post #20 of 23 Old 09-10-2006
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My 5hp o/b is doesn't have cooling water running through it!

I inhereted it with the boat recently.

I've flushed it.
A mech looked at it twice (only charged me once).
Impelar in the books does not fit the motor. (Tohatsu 1997)
Kind-of a mystery right now on how to get the water pump fixed.

Gear shifter handle is broke off at the base, and motor now requires a body twist and a "trick" to get it to shift into F-N-R.

Handle for strbd mounting bolt is broke - needs "vice-gripe-adapter" mechansim. This upgrade also useful on broker gear shifter!

Starts real well, though! Water pump issue has me befuddled. Seems like all I need is little rubber impellar. I guess I am adding up problems in order to make an excuse for getting new motor.

. . . but its alot of work trying to leave the Marina under sail. Tacking out a 100' wide channel against a stong wind . . . those darn pilings keep poppi
ng up everywhere!!
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