56 15HP Evinrude.

[GMCAMARO]

I own a 56' Evinrude 15HP. Over the winter, I replaced the plugs, rebuilt the carburetor, and timed it, per the Clymer book. Before all of this when the motor was first started or cold the engine would back fire through the exhaust. After all of this it still back fires through the exhaust, especially when first started or at very low ideal. The top end is stronger but in general the motor does not run well. Help would be wonderful.

 

[DJ]

Re: 56 15HP Evinrude.

GMCAMARO,<br /><br />My first thought s would be about timing and making sure the plug wires are on the right cylinders.<br /><br />Also, is the flywheel tight with the key lined up?

 

[GMCAMARO]

Re: 56 15HP Evinrude.

If the plug wires are on the wrong plugs, would the boat plan?

 

[mncafik]

Re: 56 15HP Evinrude.

It is possible that if the flywheel was not tightned properly, that it sheared the key and rotated a bit, throwing out the timing... this happened to me.. replaced everything - to find out it was a 25cent piece of steel.. You will need a puller to pull the flywheel to tell.. I bought a universal puller from canadian tire.. worked great....<br /><br />Mike

 

[Paul Moir]

Re: 56 15HP Evinrude.

Not to get off subject here, but on a magneto engine, like a '56 15hp, a sheared flywheel key will not affect timing, since that's derrived from the cam on the crankshaft. Rather, weak or lost spark should be the result since the magnet would most likely not be over the correct ignition coil when the breaker points opened.<br /><br />GMACAMARO - is the plate under your flywheel loose? That will throw your timing off, since the breaker points are mounted to that plate. Have you ever had the chance to examine the ignition coils? Are either cracked?

 

[DHPMARINE]

Re: 56 15HP Evinrude.

Paul,Good call.I've been calling it out of time falsely.But maybe part of it is because the customers accept it easier? GRIN<br /><br />GMACAMARO.your engine may simply be worn out.BUT How have you adjusted the carb?After initial turn settings,get on the lake,or in a test tank.Open up to full,in gear,speed.Adjust bottom needle (high speed) to best output.Idle down (in gear)and adjust top needle (low speed) to best idle.That's the way to do it.<br />If you have too much play between the mag plate and the engine block (pivot point) add some shim stock.This will lessen the point gap variance.<br />DHP

 

[GMCAMARO]

Re: 56 15HP Evinrude.

What I am discovering is that the high speed idle, does not do that much, I have removed the knob and then started with the needle 5/8 of a full turn out, from the seat position. I am not getting any change as I turn the needle. The low speed needle does work, but I as I get a real nice ideal it starts back firing.

 

[alcan]

Re: 56 15HP Evinrude.

Hi GMC<br />Your carb uses two needles, one high speed, one low speed (idle). The high speed needle can only be adjusted at full throtle. The setting to start with the high speed needle is one full turn out from seated. The high speed needle meters fuel into the bowl where the main nozzle of the carb can suck it out and spray it into the engine. Now the low speed circut sucks its fuel from this same bowl. So if your tooo lean on the high speed needle the low speed can't get enough fuel either. This is the reason for setting the hi-speed needle first. The begining setting for the low speed needle is one and a half turns

 

[GMCAMARO]

Re: 56 15HP Evinrude.

Is the beginning setting for the high speed 5/8 of a turn?

 

[alcan]

Re: 56 15HP Evinrude.

Hi Gmc<br />Remove the high speed needle. Look at the tapered end (the sharp end). Make sure it is not buggered up. If the angle of the taper is accute (long and skinny) as apposed wide (short and fat). The longer needles need to be opened more. The begining setting on the high speed needle for your motor is 3/4s to one full turn open from lightly seated. Aso make sure that the packing nut around both needle are snug. There should be some resistance while turning the needles. If the packing nut are loose or not snug enough you may get an air leak past the needles. Try this, loosen the packing nuts, so the needle turns more easily (if possible,if not don't worry).This should help you feel better when the needle bottoms out. Sometimes the needles will be tight and when turned in they will feel seated,but in fact they are not. Remember to back the needles out off the seats before snugging the packing nuts. To tighten the packing nuts down while the needles were seated would jam them into seat and cause damage. Post your email adderss and I will send you some info.

 

[BillP]

Re: 56 15HP Evinrude.

I owned a 1956 15hp Evinrude for several years. Maybe the problem is just a super lean low speed setting.