1978 Johnson 85hp troubles

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clemsonteg

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So I started a thread a few days ago about the rpm on my boat http://forums.iboats.com/showthread.php?t=498166. Yesterday I replaced the plugs and did a de-carb with deadpan and today I took it out for testing. I throttled it up and she got to 4500 rpms and held fine at 20 mph. So we stopped and shut it down to trim the motor down 1 notch because I was getting some ventilation while turning. Afterwards it went back to not wanting to go over 3000 to 3500 rpm. Any ideas? Compression is good spark is good I'm not sure what else to check.
 
fireman57

fireman57

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Re: 1978 Johnson 85hp troubles

Sounds like you might be losing spark due an intermittent power pack. Is there somewhere to borrow a known good one and put it on? If not I hate to have someone spend that kind of money on a non-returnable expensive part. Check spark when this happens. You also might have a sticking needle valve in a carb. When you tilt them for trailering or adjusting sometimes they will stick. They put a coating on them now that I hate because it makes them more prone to sticking.
 
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clemsonteg

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Re: 1978 Johnson 85hp troubles

fireman57 said:
Sounds like you might be losing spark due an intermittent power pack. Is there somewhere to borrow a known good one and put it on? If not I hate to have someone spend that kind of money on a non-returnable expensive part. Check spark when this happens. You also might have a sticking needle valve in a carb. When you tilt them for trailering or adjusting sometimes they will stick. They put a coating on them now that I hate because it makes them more prone to sticking.
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The language confuses me a little bit. When you say power pack do you mean the cdi box? The only thing I found tonight after I got back is I had one plug wire that if I turned it just right it would arc from the side which it shouldn't. So hopefully the marine shop will have a coil in stock so I can replace it and try again tomorrow. If that doesn't get it then I guess I'm rebuilding carburetors.
 
fireman57

fireman57

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Re: 1978 Johnson 85hp troubles

When I say power pack I should say cdi. If your plug wire arcs then it is bad not your coil. You might not have to tear your carbs apart. Pull your plugs and crank the engine and watch for a mist to come out of the spark plug holes. No mist no fuel and go from there.
 
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clemsonteg

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Re: 1978 Johnson 85hp troubles

fireman57 said:
When I say power pack I should say cdi. If your plug wire arcs then it is bad not your coil. You might not have to tear your carbs apart. Pull your plugs and crank the engine and watch for a mist to come out of the spark plug holes. No mist no fuel and go from there.
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Based off the old plugs I'm sure it's getting fuel. The coil in question appears to have been a used replacement because it has been spliced in with a butt connector and it looks a little different than the other ones. When I took it off today. I noticed the surround of the coil and part of the squishy middle is cracked as well so I think I would rather replace the whole coil just to make sure it's good. Can just the wire be replaced though? It looked to be built in.
 
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emdsapmgr

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Re: 1978 Johnson 85hp troubles

The later coils have replaceable ignition wires. The older ones are potted into the coil-in that case you have to repl the whole coil. You will get an (upgraded) newer style coil as a replacement from Bombardier.
 
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clemsonteg

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Re: 1978 Johnson 85hp troubles

Think I got it. Not sure what fixed it. The coil I replaced or I had the fuel line to the bottom carb was a little pinched. I'm leaning towards the coil. I plan to try to pick up some fuel line tomorrow just in case wha size is the fuel line does anyone know?
 
fireman57

fireman57

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Re: 1978 Johnson 85hp troubles

Don't know offhand. Take a piece with you to the auto parts store. Hope you got it this time. If not post back. Don't be a stranger you now have experience to share.
 
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emdsapmgr

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Re: 1978 Johnson 85hp troubles

You should note that some of the hoses under the cowling are sold as regular bulk hose. Those which have significant bends in them are special heat-formed hoses you need to get from the factory. Bulk hose won't bend around tight corners easily-they tend to pinch off the fuel flow, causing possible lean conditions. The hose to the bottom carb may be one of those hoses, since it has a factory part number: 324078.
 
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clemsonteg

Petty Officer 3rd Class
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Re: 1978 Johnson 85hp troubles

emdsapmgr said:
You should note that some of the hoses under the cowling are sold as regular bulk hose. Those which have significant bends in them are special heat-formed hoses you need to get from the factory. Bulk hose won't bend around tight corners easily-they tend to pinch off the fuel flow, causing possible lean conditions. The hose to the bottom carb may be one of those hoses, since it has a factory part number: 324078.
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Well my plan would be to go to the parts store and find a hose with a bend in it or to get a 90* elbow that I can put where the bend is if I can find out the hose size
 
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