performance mods johnson gt300

[hydroViper235]

whats the must do performance mods to get the most out of gt300?
im gona remove oil pump and do premix first. bobs low water pick-up.

[rpm racing]

remove the 4 bolts that hold it to the transom and put a merc 2.5 on the back.

SORRY....I could not resist.

[hydroViper235]

thanks, if i could afford one:rolleyes:

[prolinews]

:iagree:

[hydroViper235]

i like mercs too ,but for real. I know these v8s can be bad ass motors!

[hydroViper235]

come on guys, some info please. should i remove the vro?

[Action Dave]

You can remove the VRO and premix. Not gonna make a difference in performance. Like any OMC, to make a signifacant power gain, the motor will have to be ported by an OMC pro. There's not much bolt-on performance besides tighter heads (have to be done by a machine shop)or possibly going to a much more streamlined V6 gearcase. V6 cases don't last too long on V8's though.

[hydroViper235]

You can remove the VRO and premix. Not gonna make a difference in performance. Like any OMC, to make a signifacant power gain, the motor will have to be ported by an OMC pro. There's not much bolt-on performance besides tighter heads (have to be done by a machine shop)or possibly going to a much more streamlined V6 gearcase. V6 cases don't last too long on V8's though.

how much hp gain from porting can you expect and how much would that run?
what will get it turn higher rpm's

[ar300johnson]

go to the monty racing web site. gordon (monty) has several hp packages and can make the v-8 come alive. simpler steps are getting rid of the vro, tighter heads, and perfomance reeds. there are other omc experts on this site. racer (al stoker) is a frequent poster and has worlds of knowledge and experience.

[ar300johnson]

search monty v-8 you can see two dyno sheets on monty v-8's.

[hydroViper235]

thanks, thats what i was looking for!

[Action Dave]

how much hp gain from porting can you expect and how much would that run?
what will get it turn higher rpm's


I guess you checked the Monty Dino sheets. Serious power can be made. 400hp on pump gas is very feasible.:thumbsup:

[wideglide55]

By the time you get done spending money on it you can buy a 260 all ready to go,sell the V-8 while it still runs,buy a 260 and you will make up the hp difference with the weight savings.Going from a V-8 to a 300PM made my Eliminator faster better riding and better handling all around.Oh,one other thing, I went from wrenching,breaking down on the water and being towed back to enjoying boating more than ever with the purchase of my MERC.If you are powering a big heavy boat stick with the OMC and leave it stock ,it will live alot longer as is.

[hydroViper235]

I went with a 92 low hrs 300 xp evinrude. if it doesnt work out i will be saving for 300x. if im still young enough to enjoy it.:D
I've decided not to expect too much from the rude. gona do low water, jplate, maybe solid lowers,and reeds.

If guys no of any more diy hp mods let me know, besides swapping it for a merc.:cheers:

[gw1250]

I went with a 92 low hrs 300 xp evinrude. if it doesnt work out i will be saving for 300x. if im still young enough to enjoy it.:D
I've decided not to expect too much from the rude. gona do low water, jplate, maybe solid lowers,and reeds.

If guys no of any more diy hp mods let me know, besides swapping it for a merc.:cheers:

It's not recommended to do just solid lower mounts. You should do both uppers and lowers if you want to go with solid mounts. Good luck with your project. :thumbsup:

[hydroViper235]

It's not recommended to do just solid lower mounts. You should do both uppers and lowers if you want to go with solid mounts. Good luck with your project. :thumbsup:
Thanks, ive heard other say the the oem top mount on the 300s are really firm.