57' 7.5 head gasket, coils and sync

[ninhalo5]

Re: 57' 7.5 head gasket, coils and sync

Update:
Took it out to the river yesterday and she didn't do too bad. The waters were really calm and I probably got around 5-6 knots per hour out of her on a 14' Jon with somewhere around the max weight of people, a trolling motor that couldn't troll it's way out of a bathtub, battery, 25 lbs in anchors, and a small cooler with water and 7 lbs of ice. She still had what felt like a misfire, though not as strong as it was a few weeks ago. I can't seem to figure out why it has that sputter at WOT, so I guess I'll drop the lower end and check the dog.

 

[nwcove]

Re: 57' 7.5 head gasket, coils and sync

jmo, but if its not jumping out of gear ( feels and sounds like you hit something), you will be opening a can of worms that doesnt need to be opened!!! sounds more like you still have ignition/timing issues or fuel/air issues. also have a look at the mag plate while the engine is running.....does it wobble?

 

[ninhalo5]

Re: 57' 7.5 head gasket, coils and sync

jmo, but if its not jumping out of gear ( feels and sounds like you hit something), you will be opening a can of worms that doesnt need to be opened!!! sounds more like you still have ignition/timing issues or fuel/air issues. also have a look at the mag plate while the engine is running.....does it wobble?

It's hard to tell what it's actually doing. The engine has a shake to it but I don't believe the mag plate is wobbling. Here an vid I took a few weeks ago, and it still shakes the same. SAM 0247 - YouTube
I did notice I have to replace the gasket on my fuel tank, it's starting to bubble around 1 screw, so the tank slowly looses pressure.
Originally the engine would thunk or buck WOT now it just has a light buck or what I call a miss to it. Adjusting the carb needles in either direction will make her shutter and try to cut off.

Over all does The speed I got sound about right? I know a 7.5 hp isn't a rocket but an 8 hp blew me away 3 weeks ago, and I was doing around the same speed WOT.

I was actually planning on redoing the lower end anyhow, I think it might be taking in water. Last week I changed the oil, although no "water" came pouring out, a thick yellow oil did. A bit brighter than buttermilk, and strangely no swirls. So I'm figuring unless they make a yellow oil, then I might have a seal problem.

 

[kfa4303]

Re: 57' 7.5 head gasket, coils and sync

HI nin. Glad you got the motor running. Replacing the seals in the LU insn't too bad. All you need is a seal kit ($25), a tube of 3M 847 gasket maker, or similar product and an oil seal puller. Here's a link that can walk you through the job on a similar model.

http://forums.iboats.com/johnson-evinrude-outboards/fastwin-lower-unit-seal-faq-277190.html
Evinrude / johnson 18-20 hp LOWER UNIT disassembly - YouTube

 

[ninhalo5]

Re: 57' 7.5 head gasket, coils and sync

I got the seal and the O-ring that goes directly behind the propeller, actually got 2 seals for $5 can't beat that. All I need to get for the entire job is the rope seal and the dog itself. Unless the leak caused unseen damage.

 

[oldybutagoody]

Re: 57' 7.5 head gasket, coils and sync

I got the seal and the O-ring that goes directly behind the propeller, actually got 2 seals for $5 can't beat that. All I need to get for the entire job is the rope seal and the dog itself. Unless the leak caused unseen damage.

While you have it apart you really should change the drive shaft seal (under the water pump) and the shift shaft o-ring (under the bushing were the shift shaft goes into the lower unit). I assume you adjusted the high speed needle while you had it at wot in gear on the water. Having it adjusted correctly makes a dramatic change in power.

 

[ninhalo5]

Re: 57' 7.5 head gasket, coils and sync

I tried adjusting the high speed needle... What I did was made the initial adjustments to the carb to get her running. About 1.5 turns on the bottom and around 1 turn on the top, then I played it by ear while she was in the bucket. I found the smoothest setting while idling then when I went out to the river. A half turn of either dial in either direction would cause loss of power and sputtering, I moved the needles back and she was running again.

 

[kfa4303]

Re: 57' 7.5 head gasket, coils and sync

That's about right. It only takes small adjustments to either needle. Generally, you want to get it running in the test tank then take it out on the open water. You can dial in a nice idle by adjusting the low speed idle needle in 1/8-1/4 turn increments. You need to allow about 10-15 seconds for the adjustment to take effect. Turning the need in "leans" out the mix (i.e. reduces the ratio of fuel to air) causing a hotter, faster burn, which raises the rpms. Conversely, backing the screw out "fattens" or makes the mix "rich" (i.e. increases the ratio of fuel to air) which lowers the rpms. There is also a small, white, nylon set screw on the base of the tiller which is used to advance or retard the timing. Turning it is advances the spark a bit and raises the rpms, while backing it out retards the spark and slow the idle. The trick is to strike a balance between the the lo speed needle and the timing. Setting the hi speed needle is a little trickier as you have to do it while underway. Again, you only need to make small adjustments of 1/8-1/4 of a turn then allow 10-15 seconds for it to take effect. Here's a vid of a motor like yours in action.

1957 Johnson 10hp Outboard Motor - YouTube

Running an antique outboard 1957 Johnson - YouTube

1956 Johnson AD-10 7.5hp outboard motor - YouTube

1957 Johnson 7.5hp model AD-11 - YouTube

 

[oldybutagoody]

Re: 57' 7.5 head gasket, coils and sync

I tried adjusting the high speed needle... What I did was made the initial adjustments to the carb to get her running. About 1.5 turns on the bottom and around 1 turn on the top, then I played it by ear while she was in the bucket. I found the smoothest setting while idling then when I went out to the river. A half turn of either dial in either direction would cause loss of power and sputtering, I moved the needles back and she was running again.

Sounds like you are one the right track. Remember, you can set the idle (low speed) needle while in the bucket but you HAVE to set the high speed while it is in the river, on the boat under load and at wot. While you have it at wot, turn the high speed needle in an 1/8 inch at a time until it stumbles, then back out 1/4 turn. You don't want to run it too lean thinking it will save gas because that will also lean out the oil it gets too. It's a fine line between too much and too little but the only way to set the high speed needle is under load and at wot. Get it right and it makes a big increase in power. Good luck.