1977 Johnson 75HP Bad Pack, Stator, or Timer Base

[krogie]

Re: 1977 Johnson 75HP Bad Pack, Stator, or Timer Base

i do not own your exact motor but i have worked on a few , i can say thay that i own a 76 model johnson 85 abd they will go threw a power pack every 2-3 years ( just the nature of the motor ). maybe that is something to keep in mind with yours.

 

[DoubleBarS]

Re: 1977 Johnson 75HP Bad Pack, Stator, or Timer Base

Every 2-3 years...huh. That sucks. Is it possible in your case there is another component not up to par that is frying power packs? It just seems silly that an expensive component like this would go out that often.

I think I'm going to go ahead and replace my coils and rectifier just to make sure I don't have a failing component that fried the original pack.

 

[jay_merrill]

Re: 1977 Johnson 75HP Bad Pack, Stator, or Timer Base

Some say that a weak stator is the primary cause of premature powerpack failures. I can't say that I know that for a fact, but perhaps some of the former OMC mechs here will offer an opinion.

 

[jay_merrill]

Re: 1977 Johnson 75HP Bad Pack, Stator, or Timer Base

Can a bad rectifier cause a power pack to go out, or will it just make it ground out?

The rectifier converts the 300VAC that the stator produces to DC voltage for the charge system, while the powerpack recieves its power directly from the stator, so I wouldn't think the rectifier would be the cause of a failed powerpack. See my other post about a weak stator.

 

[DoubleBarS]

Re: 1977 Johnson 75HP Bad Pack, Stator, or Timer Base

Hey Guys,

I got the new rectifier on, but my boat mechanic suggested I wait on the coils until they actually go out. I got some other advice from him, but wanted to get some second opinions.

When I rebuilt the carbs, I noticed that the bottom carb was the only one that had a silver plug in, what I assume is, the low speed passage way. There are two holes either side of the float, and the plug was on the side with the throttle arm. The middle and top carbs had no plugs on the inside. My mechanic said that all carbs need the plugs, so I pulled the carbs and installed them, but haven't run it yet. What do ya'll think?
Did the guy before me rebuild the carbs wrong?

 

[jay_merrill]

Re: 1977 Johnson 75HP Bad Pack, Stator, or Timer Base

By "silver plugs," you could mean either the core plugs or the lead shots. In either case, yes they should all have them.

The bottom carb and the top carbs are the same, so they should look alike. The middle carb has a different part number and includes a linkage assembly that the other two carbs don't have. The upper and lower carbs also have a different choke shaft than the middle carb.

I suggest that you compare the carbs (all three) to a parts diagram, to figure out if anything is missing.

 

[DoubleBarS]

Re: 1977 Johnson 75HP Bad Pack, Stator, or Timer Base

After doing some more research, I believe these plugs are called welch plugs. I went ahead and tore the carbs apart and installed them, and it seems to run well now. No more bogging, at the dock anyway. I was up late last night swapping the motor over to my boat, and after I finish wiring her up this morning, I will be taking it out to see how she runs. I'll keep you posted.

 

[jonesg]

Re: 1977 Johnson 75HP Bad Pack, Stator, or Timer Base

I believe a bad coil can mess up a power pack, although mine went south with good coils, sometimes they just go. Next time I'm going to try cutting it open and try fix it.

You have to install welch plugs in carbs if they're missing.
http://www.youtube.com/watch?v=o5cxBMDezuU&feature=channel_page

 

[DoubleBarS]

Re: 1977 Johnson 75HP Bad Pack, Stator, or Timer Base

Hey Guys,

I just wanted to update everyone on my motor situation. After swapping the motor to my bass boat, I took it out to see how she ran, and was disappointed at first. She started bogging again. I have adjusted the timing so many times and gone through the link and sync that I'm getting sick of working on this thing. Everytime I think I finally have it (in the water on trailer at dock), I take it out and still get the bogging. It will eventually open up, but if I have another person in the boat with me, it takes even longer.

I have gone through Joe Reeves WOT timing procedure several times, and always end up readjusting at the lake. I have rebuilt the carbs again, and they are spotless. I know this motor is capable of so much more on the hole shot because I have felt it. With just me in the boat it opens up fine, but when I have anyone else in the boat, it just won't get over that "hump".

I have tried choking it when it is bogging, and it kills it. I have tried pumping the primer bulb and it has no effect.

Is the timer base supposed to max out as soon as you go into forward gear? I'm wondering if this might have something to do with it, since this is what mine does. I also have very, very little acceloration in reverse, but I can live with that. I just want a good hole shot. Also, when I go to find TDC, I am still unsure when and where I should adjust the pointer. I have gone through and found TDC turning clockwise, made a mark; and turn counter-clockwise, and made another mark, but at what position do you move the pointer?

Thanks again for all the help you have given me.