25 HP

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Fawnbay

Cadet
Joined
Jul 31, 2006
Messages
8
looking for gap on breakers and plugs gap
motor serial # is 25902DC 57055
I think that is a 1970 25 hp
also runs rough at idle- bucks when idling - does anyone have any ideas?
 
OBJ

OBJ

Supreme Mariner
Joined
Dec 27, 2002
Messages
10,161
Re: 25 HP

Welcome Fawnbay!

It's a 69'.

Breaker gap is .020. Spark plug gap is .030.

Try turning the low speed adjustment screw out 3/4 turn and see if the idle improves. Or....run the low speed needle in till it GENTLY seats and then turn out 1 1/2 turns. This is the rough setting. Once in the water and the engine is warmed up, you can adjust the needle for best idle.
 
F

Fawnbay

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Joined
Jul 31, 2006
Messages
8
Re: 25 HP

replaced the breakers ,plugs and condensers today..set plugs to 30 and breakers to 20..now I have a definite "miss" at low speed ..idle adjustments did not seem to help..any thing I did wrong or any other suggestions?
Thanks
 
X

Xcusme

Commander
Joined
Apr 21, 2003
Messages
2,888
Re: 25 HP

2 things:

What did the coils look like?? Any cracks ?

When you set the point gap. Did you align the points rub block with the crankshaft key, before setting the gap?
 
F

Fawnbay

Cadet
Joined
Jul 31, 2006
Messages
8
Re: 25 HP

yes-points set at "top" indicator on the shaft...maybe they slipped? Coils looked fine as did everything else I could see. Any other issues that could affect timing? Possible carbon buid up? Miss doesnot seem to appear at idle, only at slow to midrange speed.
Thanks again
 
P

Paul Moir

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Nov 5, 2002
Messages
6,847
Re: 25 HP

Double check the points gap to be sure and clean them really well. If you didn't tuck the wires for the condensors, etc, down real well they may be rubbing on the flywheel.

If you've got decent spark you must have at least close timing. Run through the link & sync, and then recheck the carb settings.

Mid-range trouble suggests either ignition or link & sync. A healthy ignition system will produce sparks 3/8" long appx.
 
F

Fawnbay

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Jul 31, 2006
Messages
8
Re: 25 HP

Today I rechecked the point gaps . they were ok. also checked the condenser wires and they were lower than the coils so I don't think they were hitting the flywheel. I test ran the engine and it was worse than the other day.

Earlier post mentioned " Did you align the points rub block with the crankshaft key, before setting the gap?" Did this mean I should have set the points at the keyway for the flywheel, instead of the "little arrow" next to the word "top" that was on the crankshaft?

Also as a newbie to engine repairs, what does "Run through the link & sync, and then recheck the carb settings." mean?

Thanks again for the great assistance on the forum.

Fawnbay

On the shores of Lake Couchiching , Orillia, Ontario Canada.
 
G

G DANE

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Nov 24, 2001
Messages
2,476
Re: 25 HP

There are usualy two marks on the cam, one "top" and one "set" Rub blocks should rest at cam at the "set" mark when adjusting gap. After setting and putting flywheel back on, test spark by letting both sparks jump equal gap at around 1/4". If both do with a clear blue flame, spark isnt the issue. It sounds like you either need a good carb cleaning or richer low speed adjustment, by simply turning the low speed needle slightly out. When rereading your post, it seems like the miss only occurs when accelerating. Try pressing primer bulb when problem occurs. If that helps, chances are you have a weak fuel pump, or airleak in line or plug at tank/motor, hose connections. If that dont help, remove carb and take a close look at the small orifices just above butterfly. At midrange the motor gets major part of mixture thru the small openings on intake side of throttle butterfly. Clean them with a hair from a wire brush or so.
 
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Paul Moir

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Re: 25 HP

Apologies, I keep overlooking this thread due to the subject heading.

Link & sync

This synchronizes the carb's throttle plate with the ignition timing. The carb's throttle plate is activated by a follower that runs on a long ramp (cam) bolted to the armature plate. The armature plate is the part that the coils are attached to which rotates with the throttle.

The way to set this is to have the carb's throttle plate just begin to open when the follower is right between the two marks on the cam. You can make the throttle plate's movement more clear if you attach a stiff wire to the throttle plate shaft. To adjust the movement, loosen the clamp on the throttle plate shaft.
 
F

Fawnbay

Cadet
Joined
Jul 31, 2006
Messages
8
Re: 25 HP

Thanks for the explanation of Link & Sync. I understood what you were saying. It all appears good when I check it on the engine. Now that I understand about the armature plate moving, this brings one question to mind. Should I be setting the gap at the full open throttle position, idle position, or some where in between. It sure seems to make a difference when the crank does not move ,but when the armuture moves it changes.

Also, I could not find any mark on the cam
except " ^ top ". I have been setting the gap at the " ^ " mark. Is this correct?

The fuel pump was new last year, and I could not find any air leaks in the fuel lines. Spark seems to be good on both plugs. I have not removed the carb yet, that will be my next venture!

Thanks again for the great forum.
 
P

Paul Moir

Admiral
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Nov 5, 2002
Messages
6,847
Re: 25 HP

Some cams only have "TOP" to identify which side of them should face up. I'm not certain what yours should have.

The points should be set so they open .020" maximum. This is independent of the plate position. Well really it does depend on it but it is irrelevant since you can just turn the engine over until it opens fully. Typically this happens when the flywheel key is "pointing" to the rubbing block on the point.

Pumping the primer bulb like GDANE says will override the fuel pump and any possible air leaks. It's a great test that eliminates a number of potential problems.
 
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