300x Stroker-What's Needed

[Liberator*21]

Good question.......

[Simon]

4-6 mph

[Chaz]

i just wonder for all the expense involved(those cranks aren't common and you'd probably have to buy new) is it really worth it for 200 cc's? maybe the money would be better spent in porting/crankcase improvements? i'd like to see a dyno run between 2 identical engines w/ the stroke increase being the only thing changed

Thats a really good question . As we know it's all the little things that add up to the total package. In this case it's a little smaller gain than advertized.
A 3.0 litre is actually 3032 cc / 185 ci ... 92 x 76 / 3.630 x 3
A 3.2 litre is actually 3160 cc / 193 ci ... 92 x 79 / 3.630 x 3.118
So in a shooting from the hip calculation of 300 hp from 185 ci , or 1.62 hp per ci and barring nothing else changing except for adding 128 cc / 8 ci .. I see it as having the ability to produce 13 hp more .. or just over 2 hp per cyl .
Without sitting down and plotting it out with a degree wheel . I would say that by leaving the pistons alone and taking half ( aprox .060) of the additional stroke out of the head , in essence you are killing the port timing of an already lazy map. I would think it would be wiser to cut the crown of the piston and bring the port floor down to the piston at BDC . This would in esence increase the size of the port but still keep the timing events closer to the factory specs. Unless you plan on spraying it , then the ring will respond quicker to pressure diferential as well .. ( I dont hear too much about vert or lat gas ports on outboards ? )
Is it worth the money ( crank, machine work, normal parts, r+r ) .. for 13 hp .. ? I guess only the guy opening his wallet can answer that. Is 13 hp worth 4-6 mph as Eric sugguests .. ? I cant answer that .. but I do know to make my car pick up a tenth and about 7 mph in the quarter it took over 150 hp .. but then thats making a move from the low 190's to bust 200 mph ..
I think a better bank for the buck would be to come up with a set of rods that will live to 8k and then bring the rest of the stuff along to support power at that level ... I know .. the last move would be to put the big crank in there too .. after it's been offset ground ...

Charlie ... II

[Skater 32]

I"M not sure about all that , all I know I gave Shaun Torrente a pair of 225 HP 3 Litres that will be 375 HP when I get them back next week . Yes Gas prices are crazy and think about looking for pair DFI Powerheads

[mrcrsr]

good point, it definetely throws the port timing off, bringing the rpm range down w/o changing the timing. you'd definetely have to use the degree wheel to figure that out. i know w/ mine i've already picked up 12 mph over the stock 250 efi, w/ all the mods to the engine i've done, and started w/ a 1000$ core,which i could imagine the crank alone costs that or more, but i never ran a 300x on my boat to do a fair comparison, and i probably will gain another 7 plus mph once i finish tuning the wolf, and i have another 3 litre on the bench that i'm going to modify further that started as a blown up optimax that i got for next to nothing, i think i'd rather spend that money on the wolf ecu, this weekend i managed to do a 91 mile run, and burned 28 gallons doing it, which is better then my 2.5 ever got on this boat, and we cruised at 75 mph and ran 90 mph many times, thats slitely over 3 mpg

[Skater 32]

Very nice !!

[diegoj220]

good point, it definetely throws the port timing off, bringing the rpm range down w/o changing the timing. you'd definetely have to use the degree wheel to figure that out. i know w/ mine i've already picked up 12 mph over the stock 250 efi, w/ all the mods to the engine i've done, and started w/ a 1000$ core,which i could imagine the crank alone costs that or more, but i never ran a 300x on my boat to do a fair comparison, and i probably will gain another 7 plus mph once i finish tuning the wolf, and i have another 3 litre on the bench that i'm going to modify further that started as a blown up optimax that i got for next to nothing, i think i'd rather spend that money on the wolf ecu, this weekend i managed to do a 91 mile run, and burned 28 gallons doing it, which is better then my 2.5 ever got on this boat, and we cruised at 75 mph and ran 90 mph many times, thats slitely over 3 mpg

Which mods did you do to the stock 250 to gain 12mph?

[diegoj220]

4-6 mph

Hey Simon, I have some questions for you about 3.0L engines,

I have 2 250 efi lastest model and I would like to do some upgrades to them for higher Hp, If I put some 300x C16 heads on, what are the pros and cons of doing it, and also what else do I need to change from stock rather than carbon fiber reeds in order to made them work fine and "safely". is it worthy? and how much more hp should I get with those heads.
Can I also swap stock ecu's for 300x ones?
Right now both engines are arround 120psi in all cylinders. C15 original heads