2.5 efi mods in Jet boat???

[vinnie6]

Hey All,
Looking for some help for engine mods.

Yes I have a Jet Boat...sorry out board gurus. I have to say I like them all. Dont care how much fuel it uses... As long as it has an engine I can make scream... I dont care if its a ride on lawn mower... I'll try to make it faster.

Any web sites with EFI maps or rev limiter options.

Can the 2.5's take another 500 or 1000 rpm's???

Any help is appreciated.
Thanks!

Great forum...glad I found it

[jrumon]

If you have the (2.5L) 210HP EFI jet, mods can be done to bring it up to the 240 mark...all with Merc factory parts. Go do some cross referencing on what is different. As far as RPM is concerned, the extra 1000RPM is still very safe on the powerhead, but the jet pump may not like the extra heat on the gear set and the pump might already be "maxed out" to your current set-up. Without getting into a whole flow/load theory of a jet pump, I would say that an extra 5MPH is probably not worth the investment...you could buy a real jet boat with a V8 and get better speed for the same money or less than you probably have in the "jet bath tub". What model boat and motor HP do your have anyway??? What speed are you getting??? Is the pump and impeller in A-1 condition??? What speed do you have in mind????:confused:

[vinnie6]

Thanks.....
I have the 240 EFI mercury.
Does 55.

I saw the other Mercury engines spinning higher to 7200 & 7500 r'S

I called Mercury...thy were very hush hush on th whole deal...I asked if the internals were the same...crank, heads, block etc. as the 280 horse v6 off shore.

The guy said yes. I asked if the computer is then the only difference. He said he wasnt alloed to tell me.

Sounds like the computer is the only difference and I can spin it up with no damage.
As far as the pump unit goes I dont know. If I can change the computer and hit 60 I'm happy.

It's just a bang around boat to have some fun in.
If I wanted real crazy speed obviously a V8 is the ticket. Would build something like my very worked ZZ4 with AFR heads etc....with 470 horse in my old Vette.

So where do I get a computer? Waddya think?
Big Thanks, Vinnie

[Rickracer]

His PCU can replace your stock Merc ECU, and it can be adjusted several different ways. And the price is less than a new Merc ECU. Click on his ad top right of this page, and you can either email or call. I'm sure he can answer any questions you may have about how it works. :cool:

[jrumon]

I have heard that the Sport-jet 240 EFI is the same basic powerhead as the 2.5L "Pro-Max" but not the offshore model. It may be similar the the 280HP version, but would have lower compression heads, slightly smaller EFI set-up, and so forth (hence lower rpm potential). Again, find someone in the Merc parts business that would run part numbers for everything and compare it for yourself... Merc surely isn't going to tell you a $5500 powerhead is the same as a $9500 powerhead . As far as I know, the basic electronics should be the same, so if you can borrow an offshore ECU, plug it in and try it...you never know. They are spendy even used $400-$900, look in the parts section of "screamandfly.com" or "screamandflyoffshore.com" but I would really ask around first....Someone out there must have tried it by now.... Jim.

[Blade]

34cc heads, send computer to matt riddle ,i believe he does all the mods for the comp around here ,tuner, hog out the shoe,sharpen grates,polish the inside of pump, polish and profile your 4 blade?- stainless impeller,grind reverse gate pins flush with inside of barrel,if the metal tangs are still on top and bottom of exhuast pipe remove them.finally like a glass boat the bottom HAS TO BE STRAIGHT,paint bottom with a speed coat and sand with 320 grit.are you checkin speed with a GPS?unless youve done some of the mods i mentioned already your speed is more probably like 51-53. hope this helps.i am running a 18'X56'' flatbottom with a 03 Merc 250xs 7 5/8'' pump,what are you runnin?

[vinnie6]

Cool guys, thanks.
I can never leave anything I own stock. I think I'm also one of the very few that blew up a Yamaha V Max bike engine if that gives any insight to my motorhead genetic disorder.


Right now theboat is 100 percent stock. Looks like this will be a fun winter project. With the above mods what kind of speed should I expect.

Wish Sea Doo made a twin v6 killer. it would be much easier.
:D