1978 johnson 150 wont go full throttle

[10Rams]

Hello i bought a 1978 johnson 150 not long ago recently took it to the lake and whenever i give it full throttle it sounds like it just stays at half throttle. rpm's do not increase it will only go about 10 - 15 mph. i have cleaned the carbs aswell. fresh gas. not sure what else to check as this is my first boat. thanks!

 

[Hooligan Diver]

Does it run OK otherwise? Like on the hose....? I'm having similar issues with loss of power while under load, looking like a power pack/CDI. Not sure yet how to confirm, but I'm likely to replace it anyway as it is much older than the one on the other bank.
I was told to run on the hose or in a tub until warmed up. Then, pull plug wires one at a time while running and listen for change. If it doesn't change, that cylinder is cold, if it gets rough, that one is hot.....
Hope it helps.

 

[10Rams]

yes runs fine on the hose. let me know if you find out anything thanks!!

 

[Hooligan Diver]

Will do, someone more qualified will likely chime in. It just sounds like the same sort of thing I'm trying to pinpoint.

 

[10Rams]

bump. anyone???

 

[Hooligan Diver]

Did you do the test I mentioned?
My engine was running ever so slightly on the rough side, even after warmed. I let it idle and went to the port bank first. Niether of the top 2 plug wires I pulled seemed to make any difference in the way it ran, the third, bottom one did. When I went to the starboard bank, all three wires would cause it to get worse when pulled.
This told me that the top 2 on port were cold, at least intermitantly. The power pack/CDI on that bank was many years older than that on starboard, so it made good sence to me. (It's obvious one has already been replaced)
I've ordered new packs and wires for both banks and should have them tomorrow afternoon. I'll post up when I get them installed.

 

[10Rams]

No i have not yet. im a little ways away from my boat atm. wanting to get all the info i can before i make the trip to start troubleshooting. let me know how it goes tomorrow. Thanks man.

 

[10Rams]

Anything hooligan?

 

[Hooligan Diver]

Got my parts today, a day late. I'll be putting them on tomorrow........going to have to retrofit some connections.
Some of the coils and one of the power packs have been replaced previously with newer components, hence dissimilar plugs. I'm going to have to rewire most everything in order to make it work. I'm out of time, so I am going to retrofit the plugs from the old packs to the new ones in order to let the engine plugs remain as they are........

 

[Hooligan Diver]

http://forums.iboats.com/forum/engi...n-235-power-loss-under-load-forward-gear-only

 

[10Rams]

Thanks alot man. I gkt a chance to pull a couple wires i pulled the top right and nothibg happend i pulled the one under that and it died didnt have time to try the other 4 but the top right one did shock me sooooo.

 

[10Rams]

Also how do i tell if its the power pack of just a coil.

 

[ronward]

Easiest way to check a coil is swap it with one on another cylinder that you know is firing, if the dead cylinder follows the coil then the coil's bad.

 

[emdsapmgr]

Pulling a spark plug wire off when running is a valid "cyl drop test." A normal engine will slow each time a spark plug wire is pulled off the plug. If no rpm drop occurs when a plug wire is pulled, likely it's not firing. Coils are generally very reliable, but you can swap them as a valid test. Swapping the two power packs is also a great test. If a non-firing situation moves to the other head, when the packs are swapped, then likely that power pack is bad.

 

[10Rams]

Alright finally got time to test. Got spark on all cylinders except cyl. 4 swapped coils with on and that coil worked so i guess its safe to say its the powerpack?

 

[10Rams]

Can anyone tell me how the sensor wires go into the power pack. On the left side which i replaced i purple in 8 9green 10 blue 11 white and on ghe right it was already put to 8blue 9green 10 purple 11white. Is that right or not?

 

[1976CV16]

Same issue with my v4. Started, idled and otherwise sounded good. Launched it and didnt have any power. Now that you have spark i highly reccomend buying the oem manual. It will have schematics to help you with almost every wire you need. Put everything back the same way you took it off for now...

 

[10Rams]

I did. Just strange that the right side powerpack wires are in different places.

 

[old evin]

hello need help please.i have a 200 v6 evinrude.went to lake last week and boat ran great for three days. forth day tubed for about three hours stopping and swimming here and there turning the motor off and on countless times. went back to camp to eat and had motor off for an hour or so. went to leave and crank crank crank no pop. couldn't figure it out. got it home and disconnected the main harness in engine compartment jumped starter and it fired up. I put a new ignition switch in and crank crank crank no pop.disconnect harness and jump starter it fires up. while running with key in on position I tried to reconnect harness and it dies when the two plugs get close to each other please help

 

[Bosunsmate]

hello need help please.i have a 200 v6 evinrude.went to lake last week and boat ran great for three days. forth day tubed for about three hours stopping and swimming here and there turning the motor off and on countless times. went back to camp to eat and had motor off for an hour or so. went to leave and crank crank crank no pop. couldn't figure it out. got it home and disconnected the main harness in engine compartment jumped starter and it fired up. I put a new ignition switch in and crank crank crank no pop.disconnect harness and jump starter it fires up. while running with key in on position I tried to reconnect harness and it dies when the two plugs get close to each other please help

You will need to start a new thread to get this sorted, its forum rules.
But before you do you might just want to check a short in the lanyard safety line switch or somewhere else in the kill switch wiring, its the black wire with yellow stripe. It should have no neutral/ground connection on it unless key is in off position. Any neutral connection in it will ground out the powerpack and hence no fire