Need help on initial jetting after rebuild Johnson V4 1980 140hp

**spybot** · 04-20-2018, 04:51 AM

I have just rebuilt this motor and i stay in Scotland so getting hold of jets is a waiting game.
Hopefully some folks can give me a starting size.

The carbs are 1 5/16th" Mains are 67c Mid 29.
Carbs are of the fixed jet variety. No choke plates

Work done to motor.

All casting flaws removed from block and intake manifold.
4 new wiseco pistons (after honing)
Rods and and caps Balanced to lightest.
High Comp Heads Lapped
No Port work done other than removed the plunge marks.
Smoothed flow (removed all casting marks and sharp edges) from intake through to exhaust stuffers.
Reed Cages lapped and CCMS Sport reeds fitted.
Reed Stuffers fitted
Port matched carbs to intake manifold.
New carb kits fitted.
New Fuel Pump
New Primer
New Fuellines

Motor is a 1980 Johnson V4 140 crossflow

I am after a starting point with the jets.
They take a while to get here will order a few sets but where should i start.
I dont want a race engine hence the very mild mods but would like a decent bit of power out of it.
Its going on a 16ft 660lbs Ski-Speedboat
But i will not be towing anything and normally just 2 of us in the boat.

I have 3 or 4 props to play with but really need help on the jetting.

**rjdubiel** · 04-20-2018, 07:21 AM

first things first, what compression are you at currently? that is the major factor. I have about 135-140 on my V4 and run 69's and it is rich. It is a crossflow, some heat cycles and let her rip!

**FMP** · 04-20-2018, 09:22 AM

Put a couple break-in hrs on it as was said in a previous thread before you lake run it and check compression. Take the slow deliberate break-in

**spybot** · 04-20-2018, 12:36 PM

Originally Posted by FMP

Put a couple break-in hrs on it as was said in a previous thread before you lake run it and check compression. Take the slow deliberate break-in

Thats what i tend on doing slow breakin. Double oil for the first day or so. But just need to get some jets ordered up.
Should i go to 69c? as RJ has. I would prefer it running rich than a tad on the lean side.

**FMP** · 04-20-2018, 12:55 PM

He hasn't burned his with 140psi and 69. Check your psi. Fuel and timing will play in as well. Can't talk frying fish, North Sea Dover sole

**spybot** · 04-20-2018, 03:10 PM

Originally Posted by FMP

Can't talk frying fish, North Sea Dover sole

???? Dover Sole ????

**FMP** · 04-20-2018, 03:37 PM

Yes, original name came from town of Dover fish industry. North Sea sole, Holland Sole, etc. A delicate delicious fish pan fried in butter ,dredged lightly in flour. Thin fillets done to crispy golden brown, lemon etc. Not Pacific Sole
Still too much ice around for me to catch some Crappie, yes Crappie lol

**rjdubiel** · 04-20-2018, 03:49 PM

Mine is Riverman's old rig, you can search it here, all sorts of threads on what he did. I am assuming the same as racervboat's motors as well.

**jimmbo** · 04-20-2018, 09:01 PM

Double oil for the first 10 hrs, vary the speed often, and as the time accumulates, higher rpm ranges

**racer** · 04-21-2018, 07:26 AM

Be careful comparing jets as different yr carbs jetted different.

**spybot** · 04-21-2018, 11:31 AM

Originally Posted by racer

Be careful comparing jets as different yr carbs jetted different.

The carbs are from 1980 and original with the engine. Should i go for one size up as you had mentioned in a previous post Al ?

**FMP** · 04-21-2018, 11:49 AM

Just look at the list of work you did. Cages opened up, heads cut , ports etc cleaned for more flow. Why wouldn't you try at least a couple sizes in tuning it?

**spybot** · 04-21-2018, 12:40 PM

I dont want to run the motor lean.
I received in a sorry state.
Number 3 Cylinder was toast. The piston had 1 been ruined by running lean and 2nd heat seized.
I have cured the lean situation i think by unblocking they main jet, the heat seizure was down to OTT epoxy holding the cup into the water pump. Who ever done the job had 1/2 to 3/4 blocked the pick up tube.
There is a lot of work went into this motor I dont want to leave anything to chance.
The only time i have to get the jetting right is this week. The boat gets wet next Friday for the first this season.
I can use the boat ramp at the harbor but apart from Muffs thats all i have. It is all down to fixing things before they go wrong.

**71V153** · 04-21-2018, 01:27 PM

I'd run the carbs as is before monkeying around with jets. I run stock '83 140 carbs on my '77. Same mods as yours plus scalloped block and pistons. '78 hi-comp heads with a lil knocked off. If anything it runs a lil rich, but I'm okay with that.

Go ahead and run it through a few heat cycles on the muffs.

**spybot** · 04-22-2018, 06:32 AM

So will go with the idea of running the stock jets to start with. I will order a set 1 size bigger just in case she is a tad lean but after reading some of the above posts hopefully the Stock 67c will be fine. Just in the final stages of assembly. Jobs still to do.
Make a new wiring loom.
Fit all electrics Stator timer base ect.
Then hopefully get her fired up in the next couple of days. It seems the more i look at her the more i see still needs done. With the amount of work done to the motor i dont want any surprises when it starts up for the first time.