Comparison/Performance of Merc 20H, 25Huricanne, and 25SS/XS

[RickHex]

Hi, I've just joined here and am in my 40's with a few kids on the way and I'm looking into building a 9' to 11' runabout or hydro over the next few years and hopefully getting my kids involved once they become old enough as we live near a lake and my wife and I enjoy boating and racing. I'm into car drag racing, but used to own a runnabout years back.... I'm thinking of selling my 600 HP 69 Chevelle SS396 that I'v ehad since I was 15 and getting addrenaline from a fast little boat.

When I was 13 (back in the late 70's) I was given a beat up 10' runabout and I found a few Merc. Hurricane 25's in a neighbors garbage that were all torn apart. Even at that age I was pretty good with engines and was able to dig up some new rings, bearings, and gaskets from my dad's friend who owned a Mercury dealership in Ransomville, NY and build one good outboard out of all the pieces. I will never forget racing that boat up and down the lower Niagara River near Lewiston/Youngstown, NY and now that I'm right next to lake in Hickory/Granite Falls, NC, the hydro bug has got my attention.

Being a diehard Mercury fan I was hoping that you guys could bring me up to speed on the differences and advantages/disadvantages of the Merc. Mark Mark 20H (with and without the larger carb, "corn popper" lower unit conversion), Merc. Mark 25, and the new 25SS and 25XS engines? Am I missing any other Merc. engines? Do they all fit the A-B racing lower unit and wil the corn popper conversion lower unit only fit on the 20H engine? Which one is best?

I want to work with one of these older Mercs, but am looking for something fast (maybe 60+ mph potential) and that I can eventually improve upon/modify as I'm a metallugical and ceramic engineer and love to tinker with racing engines, transmissions, and lower units... Whats the difference in HP potential and performance in the above engines? Any big advantages of one engine and/or lower unit over the others?

With this group of engines am I best to start in a Runabout or Hydro B/B1 class or something like the modified 250 class? I'm still trying to figure out the different classes and engines that can be used. Perhaps I should look at the next class up and the Mark 30H if this makes more power?

At some point in the near future I'd like to start collecting engine/lower unit parts once I decide what to get so I can start tinkering as I really enjoy (or at least had a blast back in the 70's) putting these little screaming engines and lower units together.....

Any advice from you guys that have been doing this for years and have lots of experience will be greatly appreciated.

Thanks!

[STEVE FRENCH]

https://hydroracer.net/forums/showthread.php?t=15348

This in MY opinion is the easiest, cheapest,most simple motor to build/buy today........everything from the power head down can be bought new from Racing Outboards Inc new
...........22CI OMC Powerheads (18-25HP) are avail/cheep at yer local salvage yard/Marina/E-bay.......most will bolt on and compete with a little tune-up.
Merc 200/20HP power heads are plentifull....25ss /20H towers+foots are a little more money /time to find/build right now but can be found.
I'm tempted to retire and start build'n/offer'n these two motors cause I think they would help swell the ranks of AMH/AMR in as little as two years?
You can compete with a mark 25 power head, but the Mark-28 and Merc 200/20hp is cheeper/plentiful and will out perform the 20ci motor in STOCK form.....

Later (or now if ya can budget it) .....buy a Sidewinder power head (and steer skeg extension)......and in 1/2 hour swap out time....Run ASH/ASR....or BSH/BSR.........or 20SSH........

PS....I think the motor listed above is still avail?.......Bargain price!.....I think the tower/foot adapter plate alone would be close to ask'n price...

WELCOME to the ranks of ....MODIFIED/STOCK Outboard RACE'n..................GREEEEEEEEEEEN FLAGGGGGGG !!!!!!!!...............

[jeff55v]

Welcome back to the sport Rick. Whatever engine/boat you choose to work with, you'll find a great family of competitors eager to lend a hand.
Good luck, and have fun.

[RickHex]

Steve and Jeff,

Thanks for the input and welcome!

I'm going to stick with Merc, so the OMC engines are out for me. Its sort of like a Chevy vs. Ford thing.....

I'm totally in the woods when it comes to comparing the Merc power heads and lower units except for my experience with the Mark 25 back in the 70's.

Being an engineer I understand things like HP, Torque, RPM potential, weight, and MPH in a given boat.

On the power heads if we compare the Merc. Mark 20H, Mark 25 (from the 50's), 200/20 (60's) and 25SS (from the 70's?) how do these figures compare on each engine?

On the lower units, which units fit which engine? What units are better? An A-B (which I'm not sure what that is) or the modified exhaust/corn-popper unit used on the 20H? Can this be used on the other engines?

Is there a single source or book I can get that will help answer these questions?

Thanks for bearing with me guys!

[STEVE FRENCH]

What do you have so far?

Mark-28 and Merc 200/20Hp is the way to go in merc configuration.
A STRONG 20H/COMMODE CAN BE COMPETITIVE ......But can be a lot of work/expense compared to the 22-Merc/OMC.
The Mark 28 will bolt to 20H towers (NOT THE COMMODE) ...and 25SS tower if ya leave out/relocate/adapter plate the back two studs.
The newer Merc 200/20HP powerheads will fit the 25ss tower with the 25SS adapter/spacer plate for water (although I think ya can git around the spacer if ya use yer imagination on the water passage)....early versions will need same as the Mark-28 above sentence....

That's about as easy as it gets......go for it!