In the water

[leafs]

I have a 1974 70hp johnson(stinger) it worked fine last year this year in the drive way with the muffs on it starts fine and you can shift it into gear and rev it up,but when you have it in the lake it starts fine but when you put it into gear it stalls right aways. When in the lake If I tilt up the engine so the prop is out of the water quickly start the engine put it into gear and rev it up at the same time lowering the prop into the water it goes for a few seconds then dies any ideas what is my problem.Thanks for any ideas you may have.

 

[tashasdaddy]

Re: In the water

running out of the water, and on muffs there is no backpressure on the exhaust, it should idle in the water in gear at around 650-700 rpms. on muffs 850. also could be dirty carbs. tilting out of the water running is a great way to burn up and impeller very quickly.

 

[leafs]

Re: In the water

I lower it back in the water as soon as it starts.
Also when I start the engine with the prop out of the water and put it in gear and lower the prop back in the water at the same time the revs are up and it still stalls after a couple of seconds,would this still have something to do with the idle(it seems to idle fine in the water)

 

[leafs]

Re: In the water

Could there be something wrong with the lower leg?

 

[jtexas]

Re: In the water

Will it not idle in gear at all with the prop in the water? What kind of spark plugs, how old are they and how do they look after she's been idling?

Sounds like fouled carbs. How long did it sit unused?

Your carburetors have three passages: idle, intermediate, and hi-speed. If you get one or more fouled hi-speed jets, it'll idle all day long but won't accelerate. Actually, it'll sound surprisingly good idling on two cylinders. Especially with no load on the prop.

That motor needs to be cranked & idled up to operating temp every few weeks, or winterized if you don't boat in the wintertime. Gas turns to varnish in the carburetors. Seafoam or stabil added to the gas helps.

Before you rebuild your carbs, couple things you can check:
A compression test would be a good idea, no sense pouring money into an engine with bad compression.
And make sure the timer base moves smoothly without sticking.

Revving your motor up on the muffs is a very very bad idea - just enough to keep it running while it warms up, then at idle. Otherwise you risk thermal runaway.

Also, heed tashasdad's words about running the water pump dry - the pump is pumping while you're cranking, and it'll heat up in very few seconds.

 

[leafs]

Re: In the water

It was running good last summer then before I put it away for the winter I did put fuel stab in and ran it through the system.

 

[tashasdaddy]

Re: In the water

man, there are thousand of motors that ran good last summer, it ain't now, so get over that. and lets find out whats wrong. did you try to raise the idle speed, by adjusting the idle stop screw. have you checked compression and spark, are you using new gas, or last summers gas. J texas gave very good info. with out testing, all your going to do is sit on the dock and look at the water.

if you did nothing to it, over the summer, i vote really toward clogged jets in the carb, even though, you used seafoam

 

[ezeke]

Re: In the water

For whatever reason, you are more than likely running with one dropped cylinder. Isolate that cylinder by pulling the spark plug wires one at time to see which one makes no difference.​

Once you have that cylinder isolated, you may want to inspect the ignition coil, and clean the connections carefully. If you swap the coils around, and the problem follows the coil, you will then know to replace it.​

BTW, Corrosion does not stop while the motor is in storage, so this is the right time to check and clean all of the wiring connection.​

 

[leafs]

Re: In the water

I did a compression test today the 3 cylinders are good,when the engine is running and I pull the spark plug wire of the middle cylinder the motor dies right aways,when I pull the plug wire of the top or bottom cylinder there is no change in the way it runs.

 

[jtexas]

Re: In the water

That means #2 is the only cylinder firing. To narrow it down further do a spark test on #1 & #3. Spark tester a couple bucks at autozone, set it for 1-7/8", have someone turn the engine over while you look for a sharp blue spark. Have spark on both, then carb rebuild. Best do all three while you're at it. No spark, test your coils like ezeke said - move the #2 coil first to one then the other. Post your results. Good luck.

[edited to correct a typo: should have been "7/16 inch" gap. sorry bout that.]

 

[kenmyfam]

Re: In the water

Sounds like you may have a half *ss spark that is just not enough when any kind of load is put on the motor. The guys have given you great advice so far....all you have to do now is follow up on it and report back.

 

[leafs]

Re: In the water

What do you mean by half a *ss spark

 

[ezeke]

Re: In the water

He means that there is may be spark with no load and little or none with a load on the engine.

You have it down to getting the top and bottom cylinders to fire properly. You need to determine that the coils are properly grounded and that they are working Take all of the plugs out and check for a 3/8 or better snappy blue spark. You can make a tester or buy one at the auto parts store. Just make sure it can be set up for a 3/8 or better gap.

 

[leafs]

Re: In the water

I think I found the problem ,only the middle cylinder was getting fuel, I took of the fuel lines that go to both the top and bottom carbs and sprayed in the fuel lines and the opening were the fuel line connects with the carb with carb out and ran the engine for a while it seemed to open thinks up that all 3 cylinders are now getting fuel,it starts like a charm now and when you pull off any spark plug wire it mays a differents. I plan to take it out on the water tommorrow night to see if this solved the problem.
Thanks to ever one for the advise and I hope I'm not back tommorrow night with the same problem.

 

[leafs]

Re: In the water

does anyone know about the spark plugs for my 1974 70 hp johnson
the manual say use spark plug L77J4 gab 0.030"
the only one I can find is QL77JC4 are these even close?

 

[ezeke]

Re: In the water

Use either spark plug. The Q plugs have a supressor to cut down on radio interference with your electronics.