1993 120 to 140 looper conversion

[reganr]

Does anyone know what is required to convert a 1993 johnson 120 to a 140 hp model?

I have asked many forums and all my local mechanics and still haven't received a solid answer, any help would be greatly appreciated.

Thanks, Regan

[chris_lacey]

The only difference is the intake manifold and reeds. Chris Lake (laker) has a killer V4 looper project going.
Look here: http://www.lake-effects.com/Lake%20Effects/chris_boat_news.htm

[Forkin' Crazy]

That's it? Are the cages different too?

So you are saying the carbs are the same?

I had a friend ask me the same thing last night.

Good question!:)

[chris_lacey]

Yes the cages are the different. 6 petal vs 5 petal.
BMac usually has a supply of the good manifolds. Just use the 4 throat section and discard the 2 throat part. Get the 140 reed cages and reeds and away you go.

[reganr]

aren't the 140's runnung 6 petal rubber coated cages?

[chris_lacey]

Yep, I got thinking about it and corrected my reply.

[B.Mac]

Ya need a slope-back hi-flo intake, six petal cages & reeds.
You can use your stock carbs. While your in there stick some Boyesons in it:D Laker's the guy ta' ask on these V-4's ;)
B.MAC:D

[sho305]

A couple summers ago I could have bought a 19' deckboat with a shot interior but good hull, and it had a 140 on it that they ran a bad impellor and overheated (started running funny and they shut it off). They melted the thermostats in the heads, paint had slight cracking around 2 plugs. It ran but felt like one cylinder had more bleed-down turning it by hand so I figured it needed boring. I could never figure if I was an idiot for passing on this $600 deal or not, and it came with a nice trailer also. Must have been a late 70s early 80s I'd guess and was a light blue Rude.:confused: Think I could have parted it out anyway and made out.

[reganr]

Thanks for the advice. It seems like Laker is the man. How do I get in touch with him?

[chris_lacey]

Click on the members tab, in the header, look up Laker (he's on the first page of "L"'s) and hit the email tab.

[Laker]

What I would recommend for any Looper V4 hop up is to get ahold of one of the good manifolds or good after market ones. 6 pedal reeds if you don’t already have them. Big bore carbs off the V6/V8. 1.8L Heads cced To 47cc.
Remove the air box foam and any baffles that are restricting air flow and jet up accordingly.
This will give you a nice lake motor.
After that would be to remove the exhaust can on the early style motors or cut the tuner to 11 inches on the later model one and dry stack the exhaust. Send your flywheel to performance outboards to have it lightened. Mill the heads for more compression. Light weight wrist pins, Light pistons and have finger ports cut in. Port match the castings with the sleeves. Light rods if your not going to spin it past 7500 (Probably wont anyway) V6 propshaft installed in the gearcase to run the better props.
If ya have a big budget I would get the F1 Mad EFI system.
After that it gets complicated.:)

[Forkin' Crazy]

Good info Laker.

Let's say this guy is a basser. He doesn't want to take his motor apart. Not so sure about cutting the heads either.

So intakes, reeds and cages, and gut the air box....

How much richer on the mains, air bleeds? If any?

Thanks

:cool:

[reganr]

do I need to change jets if i decide to keep my stock carbs with the better manifold & 6 petals? I Don't want to go too extreme, the boat must stay reliable, I use it to fish often!! I'd be very happy with 140 to 150 hp.

[racer]

Yes.

[Laker]

Like Racer says
Yes you will. Just removing the baffles in the air box will require jetting up.
Each motor is alittle different but I did a 130 and it needed 12 sizes bigger on the mains and 5 on the Idles and off Idles

[reganr]

What would be better? Stock 1.8 heads or MADEFI cut & oring heads?

[Laker]

For what your doing just a good set of stockers will be all you need.

[reganr]

Thanks Laker,

Will any model (year/part numer) heads from the 1.8 work, or are some better than others?

[Laker]

The 1985-1987 120-140hp 1.8L motors are what you want.
I dont have any part numbers on me as I am traveling for work.
I have also seen some later model heads cut down to work also but Allot of materal has to be taken off. What im not sure of is if the chambers are the same just deeper on the later model motors. Racer could answer this.