Ruddertwin Jugs

[chris-p]

I have not done a rebuilt on a Ruddertwin powerhead before.

Should the jugs be very tight sliding over the pistons? Almost to the point of needing a mallet to move them along? I also find it very difficult to rotate the jugs around to line up the bolt holes as well, they are very tight.

I have had these jugs nickel plated, and am wondering if that has something to do with it.

[mercuryman]

yes

[The Boat House]

New Rings? Did you check the "all" the ring gaps in
the cylinders before you put them on the piston’s?

[fisherman6]

Also, did you measure the bore with a bore gage after the plating to see if the thickness of the nickel put the bore out of spec?
-Ben

OldJohnnyRude on YouTube

[hotrod]

It sounds to me that you need to remove the cylinders to see what is wrong. Did you remove all rings and physically decarbon their grooves? Was each ring placed over its pin, facing the right direction, where it belongs ? Check all rings separately, when placed square in their cylinder, to see if the end gap is correct, which is .003-.010" for 3HP models and .006-.009" for 4HP models . The oiled cylinders should slide on fairly easily by hand after all the rings on the oiled piston enter the cylinder. A ruddertwin cast iron piston should have .0025 to .004" clearance in the cylinder. Cast iron pistons are made with less clearance than aluminum pistons. I think the plating is too thick.

[RICHARD A. WHITE]

If, as I recall, the inside of the cylinders got plated, that is your problem, too close of a fit, and that won’t fly. You will have to remove that plating somehow before continuing. Well unless you make your piston OD smaller by the amount of plating added to the bores, then you might have to trim the ends of the rings so the proper clearance is set for the piston ring end gap..

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[chris-p]

Plating went on too thick at the bottom of the jug, end of the stroke. My hones don’t seem to have an effect on it at all. Ill have to get them professionally machined now I suppose. Thanks for the help all.

Lesson learned. I tested the bore at the top of the jug only, Did not properly test the bore at the bottom of the jug, and was rushing so did not test for out of round, which it obviously is by about 7 thou.

Actually if I were to restore another Ruddertwin, I would take the time to make a proper blank for the open end of the jug, to ensure no plating got into the cylinder. I ASSumed it would be easier to hone than it is, so I just dunked the whole thing.

[chris-p]

Both jugs are very close in measurements.

Top of jug (bottom of stroke) is about 2.4960 to 2.4970
Bottom of jug (top of stroke) is about 2.4995 to 2.5045

Piston measures about 2.4995 to 2.5010

[chris-p]

Im assuming this piston is 2.5000"? (I am only using a digital vernier, my 2-3" outside micrometer is at work.

So, I believe I should have the machinist bore out the cylinders to 2.5025, which would be at the bottom end of the cylinder to bore gap posted by Hotrod. That would still leave an out of round. Perhaps I go to the upper limit of the range and bore out to 2.5040.

Ill have to check my ring end gap, see how much they are worn, and decide from there. Boring out too much may leave my end gap too high.

Are NOS rings hard to come by for these? I personally have not seen them.

[RICHARD A. WHITE]

Boring them out will be interesting as I would suspect the plating will want to flake off instead of machining out nice and pretty like…
The other concern is honing the bores out as the same may occur.
As I suggested previously having them stripped of all plating then re-plating, just the outside this time, might be the best option.
I would be highly concerned about that plating flaking off while the piston is doing its thing….

http://www.richardsoutboardtools.com
classicomctools@gmail.com

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