merc 25/xs duel carb manifold ...its ALIVE

[bobvdinghyracer]

i stated a while back , was gonna build a duel carb setup for a 25 looper here she is , almost done got some more work on inside now ... hope it works ... we will see /.......photo page is http://s218.photobucket.com/albums/cc164/bvrevrev/mod%2025xd%20intake%20plus/

[Fastjeff57]

The Merc 25 and Yamaha 25 hp are similar engines: Both roughly the same size (24 cubes) and of looper designs. Regarding the Yamaha, the only difference between their 25 and 30 hp motors is the size of the carb--the block, reeds, and etc all have the same part numbers. I realize that just going to a larger carb will not necessarily add horsepower, but in this case (the Yamaha) it does, and Bob's dual carbed monster should as well.

Jeff

[John (Taylor) Gabrowski]

I did some screwing around back in the early 1990s with having a couple of carbs on a Merc 25 loop block but went about it with doing it all from the existing front end by partitioning the reed area into 2 separate areas mechanically done and putting 2 smaller carbs to keep veloicities up on a frontal mounting flange plate system.

This was before I had anything but the empty engine blocks that had cylinder damage so it was a concept thing to see what could be done to begin with to end up with a final project later. Then I saw what it had for rods, pistons and crankshaft and the fact that because of the way the cylinders were plated there was not much you could do to the engine unless you also sleeved it but it all came down then to a puny crankshaft and puny rods easily done in when dumped by a heavy flywheel and right there the whole idea collapsed because it all seemed so weak and puny requiring major bucks needed to change the outside made the project not worth the further effort unless you had major bucks to burn on an engine that was going to run in what? The only place was some pro class and it would be outclassed there from the getgo so why do it?

Don't get me wrong that it is not an interesting project and it is, but, what it takes to make a difference and for what racing purpose is very cloudy.

[bobvdinghyracer]

hi john
dont race per say/.... like most of you guys ... but do have a dinghy race 1 time a yr and no rules , run whatya brung .. off the wall / outragoues works even better ... always wanted a radical 2 cyl an...here we go .. will it work ?soon to find out.. as far as porting it i agree .. needs sleeves and am considering on having 1 done i am not a big fan of the chrome , the flywheel is the next issue .. already have a liter one .. 4.5lbs next is a chamber have made the filler and ex manifold pipe is next ,for my purposes i dont see a problem with rods or crank they seem as good as the merc 200 type and never really had any problems with 1 as of yet anyways i am courious as to how much can be tweaked out of this motor and will find out in the very near future...........
if you think this is nuts did ya see my poor mans quickie ?.. a super ten lower gr bx mated to a mark series lower = 1.34 ratio with a mark series waterpump / bullet nose ... why ya ask cause the mark lower was trashed at threads an the sup ten broke at its mounts soooo we make 1 good unit out of 2 an end up with a stronger case , better pump and a stronger mid too but still pretty lite overall

[John (Taylor) Gabrowski]

Rat engines can be fun if you can play with them inexpensively. Seems that is the way your going to do it but cylinder liners machined, installed and ported is a machinists playground and money burns fast once that begins. :)

[bobvdinghyracer]

i no , figure apx $400 pts /labor ... but i`m thinkin if this works out power wise .........then to have a motor thats gonna last and can port some then i can justify the $ to have a block done , my investment at this time has been minimal i can do all work myself with execpetion to the liners , i have 1 mercsoil block // could port that but it neeeds a bore job an there again boring plus new oversized slugs your rite back to the $400 buck mark ... would rarher have liners in it ... does anyone kno or has anyone done porting to a chrome bore block / outboard // sled // jet ski // or ? an if so succesfully ???