Ferm, crossflow question

[spareparts]

what do you know about hopping up an old V4 cross flow. A freind of mine has a 88 spl gooing on an old 17 Formula. I found an old 140 cross flow with the bubble back exhasut plate, what will interchange motor wise, and what worth interchanging, this motor respond to any particular mod? I know my way around a V6 merc, but I don't know anything about hopping up an old Johnrude

[THEFERMANATOR]

Don't know a whole lot about increasing the ponies on em. I know that many cut the tuner down in the mid(you have to be careful with this one though as too short and it won't hardly run at all), add on the bubble back exhaust, shave the heads down some, and go with the 1 3/8" carbs. From about 77 or 78 on they will pretty well interchange most all of the parts in them. You can head over to screamandfly and spend a few days reading on crossflow mods. Some of them guys have built up some BEASTS out of the old cross-flows.

[tsubaki]

Correct me Ferm, on them I thought it was as simple as changing the reeds and carbs.
Thought there was no other difference in the V4's.
Pistons, etc. should have been the same.

[THEFERMANATOR]

Correct me Ferm, on them I thought it was as simple as changing the reeds and carbs.
Thought there was no other difference in the V4's.
Pistons, etc. should have been the same.


The early V4's used a unique piston(around 71-73 I believe). Around 77 or 78 they changed the exhaust routing and a few things in the baseplate set-up. They say you can make a new one fit an older one, but it takes quite a bit of porting and a little welding. The tuners in them vary depending upon hP rating. Up until 84 the 115 and down used a flat exhaust cover and the 125 and up used the bubble back exhaust. In 85 the 140 became the 115 since that is when they went to propshaft ratings on HP. The 85HP used 1 1/8" carbs I believe, the 115 used 1 3/16 and some used 1 5/16". The 140's used the 1 5/16" carbs and the bubble back exhaust cover with the short tuner. I could be off on the info, but this is what I have gathered from some reading on them. The monster carbs were used on the 2 thirsty 5 and the GT and XP bass boat engines.

[Steplift 72']

I believe the crossflow V-4's rated at 85, 88 and 90 hp may have been slightly less displacement than the 115-140's. I don't think that many parts interchange.

The old crossflow 115-140 motors are cheap and plentiful. Probably no more than will be spent if you tear into a 88 to boost HP.