crossflow v4

[jeffreynolds]

I am looking for info & specs on 1983 johnson 115 , got to make more power please help

[merklebob]

to make a 140 you need the tuned exhaust housing. and 140 carbs [carb are 1 3/8 vs 1 1/8-+]. the hard parts is finding what is called the filler blocks. they are wedged shaped blocks that made a flat surface for the tune exhaust partsie gaskets to mount to. the 135 or 140 hp all had the blocks. omc would never sell them as a part. the difference between the 135 and 140 is a 1" gap in the center web under the tunded exhausted.

there may be some porting changes, but i was able to do all but the carbs. my 16' sliverline granda went from 48 to 55 with just the exhaust and web cut.

[chynewalkr]

jeff, i have the same year and hp motor as you and did the conversion this past summer. use the search function here in the forums, there are at least a half dozen good threads on this exact topic. in general what merklebob said is correct, although the 140's had small changes through the years. only the 78-79 140's had the 1-3/8 carbs all others had 1-5/16. your 115 has 1-3/16.

[Ronny Jetmore]

do the 1 5/16 since the 1 3/8 won't really do much for you with a basic stock motor. if the motor doesn't have the bosses for the exhaust, you will have to "glue" in with pyro putty or believe it or not, nerstrom used bondo on the race motors. i know, i know, but it worked and he said even after running em hard, he would still have a hard time chipping the bondo out. crazy, huh? but it worked.

the 73 135 heads are good for making power, but be ready to use 30-40% av or else a rebuild.

[racervboat]

Im pretty sure you can still buy the filler blocks,we were buying them 4yrs ago when i was racing?We ran 70 mph with stock 140s and when modded we ran 85 mph lots of power to be made with crossflows.