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04-20-2018, 04:51 AM #1
Need help on initial jetting after rebuild Johnson V4 1980 140hp
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.Last edited by spybot; 04-20-2018 at 04:53 AM.
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04-20-2018, 07:21 AM #2
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!
Last edited by rjdubiel; 04-20-2018 at 07:24 AM.
1973 Viper - sold
1978 Viking - sold
1995 XB02
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04-20-2018, 09:22 AM #3Screaming And Flying!
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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
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04-20-2018, 12:36 PM #4
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04-20-2018, 12:55 PM #5Screaming And Flying!
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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
Last edited by FMP; 04-20-2018 at 01:03 PM.
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04-20-2018, 03:10 PM #6
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04-20-2018, 03:37 PM #7Screaming And Flying!
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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 lolLast edited by FMP; 04-20-2018 at 03:58 PM.
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04-20-2018, 03:49 PM #8
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.
1973 Viper - sold
1978 Viking - sold
1995 XB02
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04-20-2018, 09:01 PM #9Member
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Double oil for the first 10 hrs, vary the speed often, and as the time accumulates, higher rpm ranges
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04-21-2018, 07:26 AM #10Scream And Fly VIP
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Be careful comparing jets as different yr carbs jetted different.
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04-21-2018, 11:31 AM #11
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04-21-2018, 11:49 AM #12Screaming And Flying!
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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?
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04-21-2018, 12:40 PM #13
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.
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04-21-2018, 01:27 PM #14
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.'71 Glastron V153 - Composite rebuild - Unceremoniously wrecked
'81 Baja 15 SS - "nine-paged" '77 140
'81 Carlson C500 Metric - Currently in foster care
'70 something Speedcraft - Allison 16R clone - Undergoing restoration
'79 Carlson CVZ 19 - Far back burner
WALK TALL AND CARRY A BIG BILGE PUMP
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04-22-2018, 06:32 AM #15
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.
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