1978 Johnson 70 low power under load.

[Sashap]

1978 Johnson 70.
120 compression on all 3.
new everything electrical or replaced with good used. Perfect prop with correct pitch.
New fuel lines from tank to carbs. All tight. New fuel pump. New fuel. New gaskets the exhaust plate assembly. New head. New head gasket. New plugs. Plugs nice toasty Color. Dry. No issues there. Pump bulb on load and no difference. Choke on load no different. New carb needles. Cleaned carbs thoroughly 5 times. Checked flywheel in good condition. Checked magnets. Replaced stator. Tried 3 different power packs. New Sierra style coils and new wires. Idles and starts great. No misses on load . Just no power . No Tach but rpm sort of around 2000 by the sound. Same engine as ever on this boat and correct size. Bought non working. New rectifier. Saw fuel coming from high speed jets on load. Put hand over carbs on load and died Down as expected. Timing on load 19-20. Tdc on idle. All linkages work as expected. No Dva meter but tested what I could with regular meter and within spec on ohms. Spark gap test at 3/4" way past 7/16" and strong. Carb butterflies work as designed. All wires placed correctly and redone many times. Wire insulation all good. No shorts or faulty grounds.
Wtf?
please help.

 

[flyingscott]

Link and sync has been done and low idle timing set

 

[Gibsonman2005]

Fuel pump works properly?
Reed valves behind carb are working properly?
Double check prop and make certain no fishing line is wrapped around shaft at the gearbox?
There are three things you need to get a motor to start:
1) money
2)luck
3) beer
....wait no it's fuel compression and spark.
You clearly have comp and spark. I'd investigate the fuel system more. Make sure no water in the system including your fuel tank. My two cents good luck

 

[bass101]

When you say low power does it stay running but wont get you on plane or does it bog and die? I just started a post on a 1983 70hp yesterday sound much the same except mine has a enricher solenoid instead of choke if i hit it whlie throttling up it'll get to WOT then i"m fine. I've tried everything also..... I'm down to trying different orifices in the carbs to get more fuel midrange. Will let you know if i get anything figured out.

 

[Sashap]

Just stays at lower rpm/power. Plows through water at 8mph. Doesn't bog down rather never gets required power. Doesn't stall. New fuel pump. Rebuilt everything but pistons etc.

 

[Sashap]

Fuel lines all new and tight from new tank all the way to new pump to rebuilt and clean carbs.

 

[Sashap]

Link and sync has been done and low idle timing set

Low idle timing at the right mark. All carbs moving exactly together.

 

[bass101]

Well thats a bit different than mine. It'll just bog and die.. Good luck! Keep us updated when you figure it out.

 

[WernerF]

You didn't say anything about the boat. Length, weight, prop pitch? Any chance it is has sucked water and is too heavy now?

 

[Gibsonman2005]

I still think you have an issue with fuel system/delivery.

This may sound annoying and obvious: fuel filter is clean and properly installed? Oil/Fuel mix is proper?
Sometimes a new tank can have plastic debris inside from manufacture.
Air/fuel mix from carb is optimal? Float in carb is working?

 

[Sashap]

You didn't say anything about the boat. Length, weight, prop pitch? Any chance it is has sucked water and is too heavy now?

16ft. Been out of water for several years. Drain opened whole time. Even then engine should give power should it not? I hear people test with boat on trailer in water so same effect? Prop is 13.5x17 perfect condition.

 

[Sashap]

I still think you have an issue with fuel system/delivery.

This may sound annoying and obvious: fuel filter is clean and properly installed? Oil/Fuel mix is proper?
Sometimes a new tank can have plastic debris inside from manufacture.
Air/fuel mix from carb is optimal? Float in carb is working?

Yeah, I keep going back to that. I will check in tank prefilter. Screens clean in pump. Fuel also has seafoam in it and stabilizer. Carbs have no fuel air adjust. Can see fuel spraying evenly from all high speed jets at wot. Butterflies all in correct position. Floats all level and close needles perfect. New needles. Doesn't starve out. Just stays at low power. Didn't try spraying fuel in carbs at wot.

 

[Sashap]

Just checked fuel tank screen and it is clean and clear.

 

[Sashap]

Noticed that putting my hand over carbs one at a time that one didn't have much effect. Cleaned it again just in case. Totally spotless anyway. Then noticed new spark plug wire shorting through boot at block. Turned it away and it stopped. Don't think this was the issue because it ran poorly prior to this anyway. Why would a new wire short?

 

[Sashap]

Also put a clear lead me portion to view fuel and saw no bubbles at all so am sure no air leaks.

 

[Gibsonman2005]

And thorough prop inspection? Put in neutral with the prop off (...if you have line tangled you'll see) and try to spin the shaft by hand....have you spent much time on the LU?

 

[Sashap]

And thorough prop inspection? Put in neutral with the prop off (...if you have line tangled you'll see) and try to spin the shaft by hand....have you spent much time on the LU?

Thanks. I rebuilt the water pump and changed oil. Lower unit is clean and turns easily. Found a guy froM Campbell river with a 1986 evinrude 70 for $1200. Got that one. Still no luck with Johnson as a mechanic even tested everything and could not find an issue. Electric system works perfectly he said. Tested using manual and Dva meter. I guess I will just sell it as parts. Unless someone has any ideas???

 

[Gibsonman2005]

Ouch. I got a 1980' johnson 85hp for $250 last year.

 

[Chinewalker]

Sounds like an ignition issue. Try a cylinder drop test.... The arcing wire might indicate an issue. What plugs are you running?

 

[Sashap]

Bought another motor. 1986 evinrude 70. First time out ran ok but remote linkage needed adjustments. Did that. Also changed all fuel lines because I got a weird stall after a few minutes. Lines were all hard. All tightly sealed now. Took it out and it had a hard time getting to speed. Then ran beautiful until I stopped. After that could not get past idle. Would die. Managed to press primer button man times to nurse it up but would not get past 8 mph . Wtf???