'69 Evinrude 33HP: Throttle/Armature plate question

This is the only old Evinrude I've ever worked on. Even though I have a manual, it doesn't tell me how things should "feel".

I have the remote controls disconnected so I am working the timing advance/throttle via the lever near where the throttle cable attaches. It's the one that has the slow/start/fast indicators on it.

What i've noticed in (in neutral) is that I can turn the lever to a certain point and the armature plate stops rotating. I understand why it stops. However, I can turn it a little further. Doing so opens the throttle some more withough advancing the timing. When I let go, the spring returns it back.

The reason I'm asking is that the engine won't idle unless I turn it like I stated above. If I let go, it'll struggle a little and then die. Once it's good and warmed up it will idle with my hand off but it's really rough.

There are several adjustments I have not gone through yet, but just understanding the spring thing will be a big help.

Thanks.

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

That's really a misuse of the spring thing. Here's how it's supposed to work.

As you throttle up, the ignition needs to advance. That is to say, the spark has to go off earlier and earlier versus how close the piston is to top dead centre (up all the way). At idle the spark plug actually fires after the piston has gone up all the way, or rather on it's way downward. As the rpms pick up, it will fire before the piston reaches top dead centre so that maximum cylinder pressure happens during the piston's downward stroke. It needs to fire so early because the combustion takes a finite amount of time.

But there's a limit to how early it can fire that the engine cannot go beyond without causing serious knocking problems. This is about 36 degrees before top dead centre on a Big Twin. So it's restricted by that stop on the armature plate (part of the spark plug wire support casting) which hits a tab on the block.

Tt's possible to squeeze more power out of the engine beyond that throttle setting by allowing more fuel/air, without advancing the timing. That's where the Big Spring takes over and opens the carburetor the rest of the way.

Early on, the BT didn't have this arrangement, but rather the throttle simply operated the armature plate (without the aid fo the Big Spring). The thing about that was the fuel consumption was fairly linear with throttle position. By advancing the ignition early you were able to improve fuel efficiency greatly. When the armature plate hits it's stop but before the big spring takes over, fuel efficiency is very good. Then it goes to peices as you pour on the fuel to get the last bit of power out of the engine.

By the sounds of it, I would guess that your link & sync (ignition timing to carburation synchronization) is way off. First thing to check anyway.

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

The linkage is way out of whack and needs to be adjusted. You are describing the spark advance being limited by the interlock bar in neutral gear. At that point, the override spring and rod linking it to the carburetor should be nowhere near being operational. When the motor is in gear and the armature plate goes clear against the stop on the block, then the over-ride spring allows the rod to be moved which opens the carburetor butterfly the rest of the way. The set collar on the carburetor actuating rod is way out of adjustment.

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Thanks guys. I understand completely now the function of that spring.

I will check the sync & link (among other things) at my next opportunity.

I will also add that the indicator I mentioned above does not point to the "start" position unless I turn it far enough to actuate the big spring. If the sync & link doesn't fix that I think I saw a screw near the gear that I may have some sort of slip adjustment.

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

The pointer never does align to the wording worth a hoot, and is not adjustable except for making sure the gear teeth are properly meshed. To start the motor, just put it in neutral and advance the throttle till the armature plate goes up against the interlock bar. That's the "start" positon, no matter what the other thing says.

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

I checked the sync and link and it was a bit out. I set it according to the manual. I rather appreciated the eccentric adjustment. I've never been too fond of adjusting things that go like: loosen a screw, move something into place and tighten the screw and repeat until it's really in the right spot because the lock screw moved it. I was glad to see the point gap adjustment worked the same way too. But, I digress. With the engine off, I put it in gear and advanced the timing/throttle fully. I see how the "big spring" works. And in gear it actually locks it in the WOT position. I don't know if it's recommended running like that (I haven't) but at least to me it "feels" like it's working right.

I've got some other stuff going on not relevant to this thread so I haven't tested it yet but thanks again for the tips.

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Ok, with new points and sync & link done it seems to behaving a bit better.

With the vibration of the engine running and whatever other forces acting upon it, the armerature plate doesn't want to remain at the "start" position. If I allow it to go too far (throttling down) the engine struggles and then dies.

Is this just the nature of these old engines or is there something to adjust the friction of the armerature plate etc...?

Edit:

Another possibility I just though of is with the remote controls installed there might be enough friction there to keep it in the "start" position. And just for clarity, the start position I'm referring to is when the plate meets the lock, but not to the point where the big spring comes into play.

I wish I had a way to measure rpms on this thing too because with the cover off and running in the start position it seems kinda loud. I did put the cover on to hear it that way and it just seemed to quietly purr so maybe that's of no concern. Still it would be nice to know the rpms.

Sorry for the long posts. I just want to make sure I'm describing everything properly so you guys don't have to keep asking for more info over and over like I see in some posts.

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

The throttle friction ought to be controlled by the remote box. Usually there is an adjustment somewhere on it. There are a few different boxes so it's hard to say for sure where it should be. This is a bit of a safety feature. If the cable should break or become detached, the outboard will slow to idle.

The forces from the flywheel magnets plus the vibration will naturally push the armature plate back. It'll snap off the big spring at full throttle as well.

I find it very hard to judge the idle speed on these engines. Perhaps it comes from having a 4-stroke tuned ear. They always sound like they're idling faster than they are. Is there anything else suspicious about the idle? Oil film on the ignition coils? Both spark plugs "reading" the same? Pumping primer makes no change?

Are you aware of the various taching methods for these outboards? IR tachometers, tinytach.com, and my black box to interface a common 4-stroke tachometer?

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

The engine is on my stand with the remote controls disconnected. Your statement confirmed my theory. I think it is doing what it is supposed to. If the controls were connected I think it would stay where I left it. There is a friction adjustment on the control box. It just increases the pressure of the plastic "teeth" that ride against a gear-like part. The teeth look brand new even though the box is far from it. Looks like it would give a fine "ratchety" feel as you pushed the lever forward.

The coils are clean and dry. There is nothing coming out of the upper crank seal.

The plugs look clean. I was hoping to tell something by looking at them, but they look almost like they did when I took them out of the package. I have not ran it much so maybe with some more run time they can tell me more.

The fact that the plugs were so clean had me worried that the idle mixture was too lean which prompted me to set that per the manual. That did not go so well, but I have another post about that.

The primer bulb stays firm, but I will check again to see what it does when I squeeze it if anything.

It does seem to start and run pretty well with just a hickup now and then. The waterpump is working well and the head is staying cool enough to keep my hand on it. So cool in fact that I can stand to leave it there for as long as I want. I am only idling though so it might get hotter if in gear and throttled up. I did put it in gear once to test yesterday. It was the first time I did that since doing the impeller. Seems to work fine since I got soaked hah!

Good tips on the tachometer stuff. I will look into that. I love guages anyway.

Thanks again!

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

I pulled the plugs last night after idling for a little while. The pics have been added to my album.

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

hiccuping, sneezing, or coughing at idle is an indicator of the slow speed needle being set too lean. "Reading" spark plugs after running at idle in a barrel is almost meaningless, unless they are getting dripping wet or something.

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Re: '69 Evinrude 33HP: Throttle/Armerature plate question

Yessir... I have zero confidence that the slow needle is set right. It's got to where it coughs rather violently. Not multiple coughs but just a random single one in there from time to time. It's pretty voilent actually. The packing is missing and it just won't adjust right until I get that fixed. I can set it at the default 1.5 turns out but further adjustment just isn't working well. I'll get the good OMC carb kit soon and be done with that.