70 hp johnson mods?

[roycesrolls]

I just got an 86 70 hp johnson for one of my mini speed boat projects. I was wondering if theres any mods worth doing? Its a 20 in mid standard fishing motor. Is there any carb work or reed changes, a higher compression head or better plugs i could run? I was also thinking about a nosecone, but ive heard that on some of the smaller motors it can actually make it worse? Also are there any certain lowers with better gear ratios? Any help appreciated, or if you could steer me to the right person etc..

[HICKSTER]

hi you can cut the head to give it a little more squeeze,make the pocket depth .550 deep and you will be safe,done plenty to SST60 spec which is .450 with no problem but ussually we run 50/50 race fuel.After head cutting make sure to do a couple of plug chops to make sure not to lean,as for reeds boyesson fibres for insurance,and if noise not an issue relieve the exhaust,b sure good premium fuel and synthetic oil of choice (we run KLOTZ)and have some fun playing with setup.
good luck Paul

[HICKSTER]

sorry should have aked is it a 56" motor or a 49"
Paul

[roycesrolls]

From what ive read its a 56 motor. Is that bad? The driveshaft is a 4 spline, if that helps

[HICKSTER]

thats a good thing imo i like the extra cubes,post a picture if you can.
Paul

[roycesrolls]

I would, but i dont have any previous pictures before i started prepping it for paint. The lower is off, the two pan cowlings are off, the trim system is off, and the two brackets are off. Im stripping the motor to bare metal then priming with 3m zinc chromate epoxy primer , then awlgrip 545 , then awlgrip snow white. Its gonna look killer

[Fast Fred]

gots a clip on hear of a moded 56er makin a pull in the test tank, on a 140hp test wheel, see if i can bump it to the top, and what he said.

[johnboy 88 vegas]

What are you really gonna use this boat for.... racing or going out in the river all day to play around? If you want this motor to run hard just remember that race fuel is pretty expensive nowadays. A little insight on your intentions for this rig would help determine what all you really need to do to it.

[rev.ronnie]

A nice set of Chris Carson's reeds is a good investment in performance and insurance. Tell him what you are building and he will set you up with a set of reeds to match.

[ChrisCarsonMarine]

If the driveshaft is four spline the motor is a 49 in,I'm pretty sure.the easiest way to check...the 49 uses a head with a removable water jacket and a multi plate exhaust manifold,the 56 in motor uses a one piece head and has a cast in exhaust system with one cover plate.Someone COULD have put the older 4spline crank and lower in/on a 56 in motor.and thanks Ronnie...we do make several different reeds for there motors,for use with stock or modified cages,Chris

[sharpeye Mike]

The three first years of the 56 cu. came with 4 spline crankshaft.
Mike

[ChrisCarsonMarine]

Thanks for setting me straight there Mike,would that be 86-89?,Chris

[roycesrolls]

The motors an 86. It does have the removable water jacket on the head, and the one large exhaust cover. I'll put up some pics of the powerhead. I guess i got one of the inbetween motors. The powerhead is actually white, and clean might i add for a salt motor. I measured the gearcase width at 4 inches an its got 2.25 to 1 gears, im estimating, as i spun the driveshaft 2 1/4 times for one propshaft rotation. So basically the lower is junk lol

[sharpeye Mike]

I wouldn't say junk roycesrolls, it all depends on what you want to do with it and what boat you want to put it on.
Chris, I'm not sure if the last year was 88 or 89 but they made a 89 75 hp short shaft in 4 spline.
Mike

[Fast Fred]

best to drill oil holes for the bridges, needs a pee toob drilled into the exhaust water jacket,on the top, factory said she gets an air pocket
there and thats how they fixed it. the 2.33 foot works good. don't push the exhaust height more than 1.500 from the deck and she will keep most of the low end. SST carb specs, twin fuel pumps. if it's a lost fome case, there is a big glue line in the boost port, way best to clean them out. the 56er in the tank is 86-87, sold molded case has smooth boost port runners.

[Fast Fred]

sharpeye Mike, i looked for that mod 90short, i did not find it

[sharpeye Mike]

Good stuff Fred, about the mod 90 if you go to the bottom of the first post there's a short clip on you tube of the motor running.
p.s. I grounded your port map on my 49 minus the finger ports, will try that this year and I'll report my findings to you.
Mike