1980 70hp Johnson problems / more info & pics

[b_lish1966]

Took my boat out today and as usaul she starts right up, but just like last summer at idle can smell gas. During the first couple runs around the lake she ran great or seemed to be anyway, but during a left turn seem to loose some power and could'nt regain even once i straightened out, for the rest of the eveing that's how it ran, like maybe not getting enough fuel and also from an idle to wot it was hesitant again like it wasn'y getting fuel, also noticed some oil on the outside of the cowling and some inside, same thing happened last summer, really stumped here could use some input on where to look.

 

[b_lish1966]

Re: 1980 70hp Johnson problems

Re: 1980 70hp Johnson problems

Couple additional thoughts worthy of mentioning, the cowling for this motor says VRO, but I don't think the powerhead has a seperate oil pump and also I'm wondering if I'm loosing pressure in the fuel line and that's causing my problem. Last summer on I believe my last trip to the lake the connector to the gas tank broke and I doctored it with tape so we could go boating and haven't replaced yet, yeah I know shame on me, but seiously could it be something this simple.

 

[jtexas]

Re: 1980 70hp Johnson problems

Re: 1980 70hp Johnson problems

You sure about the year? 1980 3-cylinders did not have VRO pumps. Are you premixing your oil & gas?

Does the fuel line hold pressure? As much as I respect duct-tape field repairs, it'll be impossible to troubleshoot your symptoms while running the motor with the fuel supply line in its current condition. Gasoline will desolve the adhesive in the tape. With luck, it won't find it's way into your carbs.

But if it were mine, I'd do a compression test, spark test, inspect the spark plugs, and make sure the fuel was fresh and free from debris and water before I took it back out.

 

[iwombat]

Re: 1980 70hp Johnson problems

Re: 1980 70hp Johnson problems

I think you should look at your floats. Sounds like it's flooding in the turns.

 

[5150abf]

Re: 1980 70hp Johnson problems

Re: 1980 70hp Johnson problems

If you can smell gas you have a gas leak,and yes replace the broken coupler at the gas tank, they only cost a couple bucks and that could be your problem.

 

[b_lish1966]

Re: 1980 70hp Johnson problems / more info & pics

Model #J70TLCUR and serial #R 7446288, what year am I deal with.

 

[b_lish1966]

Re: 1980 70hp Johnson problems / more info & pics

Hope these pics help some.

 

[tashasdaddy]

Re: 1980 70hp Johnson problems / more info & pics

J10TLCU is a 1987, your looks to have some replacement parts on it. the fuel pump, is a premix pump, not VRO, who knows about the sticker. the black hose not connected, probably old oil line. looks like your fuel pump is leaking. could just be loose filter screw, in the center of the pump. or the seal is bad.

 

[jtexas]

Re: 1980 70hp Johnson problems / more info & pics

If the fuel pump diaphram is punctured, fuel will sometimes leak out the hole on the back of the pump housing. Sometimes it leaks into vacuum line flooding the engine.

Yes, there should be an air silencer bolted to the front of the carbs. It's not causing your immediate symptoms, though.

 

[b_lish1966]

Re: 1980 70hp Johnson problems / more info & pics

I took the fuel pump of the motor and took it apart and seems to be in good shape, but all the hoses were in bad shape and some clamps were loose and also the screws. I replaced hoses and clamps put everything back together, also replaced the gas tank and fuel line, hope these things make a difference on this issue, the only thing that concerns me really is the screw that fasten the fuel filter to the pump won't tighten, maybe stripped or just the wrong screw all together. Seems someone in the past just didn't take the time to put things together right.

 

[b_lish1966]

Re: 1980 70hp Johnson problems / more info & pics

This will be my last comment on this thread. The tank of gas I was using was several months old and I willing to bet that is what was causing this problem, it was down to the last gallon or two and probably had some water and other garbage in there. Lesson learned.

 

[b_lish1966]

Re: 1980 70hp Johnson problems / more info & pics

Well thought or HOPED it would be my last comment, but guess not. I probably know the answer to my problem but would prefer to put the issue out in front of some eyes and get feed back before I proceed. Took my boat out yesterday, started right up and I let it warm a bit and then headed out and at first it took right off and planed out nice but after about 30 seconds she did the same as before, lost power and couldn't get it reach WOT throttle the rest of day, it actully got worse the more I ran it and started to smoke some also, so my question is, what do you think needs to be done.

 

[jtexas]

Re: 1980 70hp Johnson problems / more info & pics

Old gas in the tank = old gas in the carbs, turning to varnish.

1st, compression test - no point throwing money at a motor with bad compression.
2nd, fix the known problems: replace broke fuel line fittings and fix fuel leak at pump.
3rd, carb rebuild.

don't run it until this is done - any cylinders starved for gas are getting dragged through a dry hole - not good.

 

[Joe Reeves]

Re: 1980 70hp Johnson problems / more info & pics

I've read the above replies. I assume that the large black plastic fuel/oil pump has been discarded and the engine has the smaller old type regular fuel pump installed....... and that you are pre-mixing oil with your gasoline.

If so, the mixture should be 1 pint of TCW-III 50/1 oil to 6 gallons of gasoline. A octane rating of 87 will be fine.

Spark plugs should be Champion QL77JC4 plugs, gapped at .040. Make sure that there are no fuel/air leaks anywhere in the fuel system.

Compression should be 100+ psi and even on all cylinders. Is it?

With the spark plugs removed, the spark should jump a 7/16" gap on all cylinders with a strong blue lightning like flame.... does it? NOTE, the 7/16" gap is important, don't attempt to test the spark using the spark plugs as that is a waste of time.

Remove the screw/bolt that you'lll see at the bottom front of the carburetor float chambers. If the back of that screw/bolt is discolored, you can be assured that the carburetor is fouled, gummed, clogged. If so, remove, clean, and rebuild them using complete carburetor kits. Be sure to manually clean the fixed brass high speed jet that is located in the middle center portion of the float chambers.

When working on carburetors, set the floats as follows:

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.

The leaking fuel connector..... hopefully you've replaced that item. If not, do so as that would allow the fuel pump to draw air.

Get back to us with what you find as per questions above etc.