1975 evinrude timing questions

[jherlyn]

Hello, I have a timing question.

So the motor is a 1975 Evinrude 75Hp Hustler 3 cylinder. The motor is slow to plane and as it comes up it revs up/bogs down. The fuel system is completely rebuilt and the spark is good and hot. So, I'm leaning over the water while another driver revs the engine up and I pull back on the advance timing arm. When I hit the right spot the boat just takes off.

So I take a timing light to the engine while its running, and at idle the mark where its hitting on the timing arrow is 12 degrees. My spark advance, btw, says it should be 16 degrees at WOT. First question, when I'm idleing should my timing light not be flashing on Top Dead Center? I mean, there shouldn't be any timing advance in idle, Right?

Anyways, so I pull the top spark plug as the manual says and test TDC by finding it with the piston. Sure enough, it looks like the flywheel is about 45 degrees too far to the Counterclockwise, which means that my fywheel pin might be sheared. I'm going to pull it tomorrow, but this leads me to my most burning question. If the flywheel is off, will it mess with the engine timing, or will the engine fire normally and I just think the timing is off? I hope I asked that in a way that people can understand. Is it there for my benefit to time the motor to a mark, or is it there because if the flywheel is off, then everything below it is off?

 

[Monte1961]

Re: 1975 evinrude timing questions

no it will not fire properly with sheared flywheel key. Post back results.

 

[jherlyn]

Re: 1975 evinrude timing questions

Thanks for the fast reply. Does anyone know whether or not on this motor that when idleing with no throttle if the timing should be hitting at TDC? Or is there a little "advance" built into the engine for warm up

 

[levi_tsk]

Re: 1975 evinrude timing questions

the timing advances fully BEFORE the butterflies open on the carbs ....

 

[Monte1961]

Re: 1975 evinrude timing questions

the timing advances fully BEFORE the butterflies open on the carbs ....

Really?

 

[Daviet]

Re: 1975 evinrude timing questions

You said that when you pulled the timing arm back it ran properly, the mag plate or arm isn't binding is it?

 

[jherlyn]

Re: 1975 evinrude timing questions

No, its fully moving, and I don't know if I agree that the timing advances before the butterfly opens the carbs. From what it seems to me according to the book it advances about halfway through the opening of the carbs at the same speed the carbs open and then hits the stop and the rest of the way to full throttle it stays still.

The only thing that I can't find in the book is when you put a timing light on it in idle, if it is supposed to read right on TDC or if its advanced a little bit. And I kind of need to know that to time it once I get the flywheel fixed.

 

[jherlyn]

Re: 1975 evinrude timing questions

Ok, so I found a chart and it says that the spark advance timing is 16 degrees, which I knew, but it has another column that says throttle pickup degrees before TDC, and mine is listed at TDC. So if I read this right that means at idle my engine should be firing at TDC......Right?

 

[levi_tsk]

Re: 1975 evinrude timing questions

yeah if that came out of a service manual id venture to say its right ... ive only worked on one 3 cylinder and it was a tohatsu and it DOES almost fully advance before the butterflies open and also on my V4 it does the same thing ... i think i checked and it picked up all but two degrees and the last two it opened the butterflies just a hair ....

 

[jherlyn]

Re: 1975 evinrude timing questions

Alright, that's perfect. I'll pull the flywheel tonight and see whats up and I'll let you know.

 

[ronsealdeath]

Re: 1975 evinrude timing questions

Just pull the flywheel, check the condition of the crank, keyway and flywheel. If all nice, replace key and torque up the flywheel nut to the specified torque. Why did it shear in the first place? No doubt because it wasnt torqued up properly before. All you need do then is follow Joe Reeves' WOT timing guide in the sticky section at the top of the forum. Job done!

Our key sheared and made a hell of a mess of the crank and flywheel. Watch out because the swarf could stuff up your stator? Clean it all off. If you have a knackered flywheel and crank then just torque the flywheel nut +25% ! It works for us and hasn't sheared a key yet in several hrs of use (famous last words). If it doesnt work nothing lost as the crank and flywheel are probably junk anyway.

 

[jherlyn]

Re: 1975 evinrude timing questions

Well, it was a journey, but the flywheel is back on.

It kind of gave me some background in this motor though, because it was obvious that there was a problem with timing before, but whoever worked on it failed to get the flywheel off and gave up. So here we go....

first thing I noticed is that the bolt holes for the harmonic balancer puller were stripped out, so somebody tried to get it off and failed. so i grabbed the puller that would pull by the teeth and took a chance. Got it to pop. Key is sheared. But everything else is fine. So I put the flywheel back on with an OMC key and put a timing light to it. the marker on the top of this motor can be adjusted to match TDC, well they buried it all the way to the left, meaning that they thought THAT would fix the problem.

Anyway....all straightened out now. Put the flywheel on and she seems to run better..way better. I'll take it to the lake this weekend and see what I got. Probably best to do it that way to tune it to performance.

 

[levi_tsk]

Re: 1975 evinrude timing questions

make sure you set the wide open timing before you go....

 

[jherlyn]

Re: 1975 evinrude timing questions

so I went out, and it did fine.....for a few runs. and then started acting funny I thought I HAD this

anyway, what its doing is surging at Wide Open Throttle. So I thought I might be losing a piston again because I replaced the coils and WAS NOT crazy about how the spark plug wire taps into the coil. In fact, during my trip they came apart....TWICE!!! So I might be looking for a better option on these down the road.

I was messing with the spark advance in open water, even though I dialed it in at home, and all of a sudden at high throttle, the motor dies, and then would not start. I had the same thing happen to me on shore earlier, and I thought it was just a low battery. After charging it it seemed to work fine. I tried to start it 2 or 3 times, then went back to the gas ball....empty. Pumped it up firm, tried to start it, ball is flat again. So I troll back to shore where after a few tries I get it to start, run a few seconds, and then die. It does this three times, then finally starts and stays running. I go back to the ball on the motor and when I pump it then engine picks up.

So, waddya think? Fuel pump? This would explain the surging at full throttle and the random dying and flat ball. I just rebuilt it three weeks ago, but since then it has fuel locked, HARD, once. Could I have messed up the diaphragm, or can you simply not rebuild these worth a damn and when its time do you just need to replace the fuel pump?