A rough and stuck Mercury KD4-1 serial # 121088 plus a spare powerhead form the basis of this Winter's basement project. A very ill treated outboard but one that has not seen enough use to show any wear on drive shaft splines or seal area. Worn splines and pitted and grooved seal ares is more usually the case. Gears excellent, shim present and like new which is rarely the case. The rest of the
story is stuck, missing and broken. Most would call this hopeless and worthless. I tend to go for junk seeking to turn it into treasure. I see it as opportunity
wrapped securely in problems. I will try to post pictures before,during and
Very nearly same as WD4
Tear down has not gone as expected. When attempting to separate powerhead from
drive shaft/exhaust housing the lower cover was firmly stuck to leg. Powerhead
separated by hammering on drive shaft. Drive shaft stuck in crankshaft socket
separated by more hammering. Applied PB Blaster to joint between cover and leg
Let it set over night then hammered it loose. Of course pistons stuck in both
cylinders tried grease gun but with limited success. Used threaded rods and nuts to force cylinders away from crankcase...with unexpected results...instead
of pulling cylinder off pistons I managed to SNAP both connecting rods. No
great loss as I did not plan on reusing rods...rusted solid to crankshaft.
At this point both cylinders are separated from crankcase but have pistons
stuck in them and lower portion of each connecting rod is still firmly fastened
Oh and my direct connection of grease gun to cylinder failed to work...check
valve not holding so I had to round up a zerk fitting for 1/8 NPT to serve
as a check valve. Funny thing is the grease gun with direct connection has worked on at least half a dozen prior problem cylinders including one as recently
Sum it up...lots of progress but in ways unanticipated and not previously traveled. It is not yet clear if any portion of powerhead can be saved but
so far nothing has been damaged that was not already junk. Grease gun pressure
was high enough to leak thru exhaust ports despite best efforts to seal with
gasket and steel covers...pressure in center port could not be contained.
1/4" thick steel cover lifted over center exhaust port only so I added another
cover and placed a bit of gasket between covers in center hoping to stop
distortion...and it lifted that as well. The swap included
a spare powerhead so nothing is needed from the stuck original but some
salvage would be nice especially after the effort so far.
Documenting with photos hopefully to post at some point.
Sunny and 60+ Not the usual November in Michigan. Tried to break pistons loose
by hammering on end of broken connecting rods...moved one piston a tad but nothing with the other. Tried grease gun with beefed up gasket again no luck.
As a final last resort took cylinders to press to push on top of piston with
rod thru spark plug hole...not always a good idea as piston may be
damaged or rod may drift off to side. Having nothing to lose and having run
out of options into the press they went. When pressing something that does
not want to give way you hear loud groans and abrupt movement with a snap or bang
sound...pistons came out. After clean up neither pistons nor cylinders
look worth the trouble. About as expected. The crankcase looks okay but
the broken connecting rods will have to be removed before crankshaft can
be pressed out. The rod cap hex head cap screws almost always need to be
heated before they can be removed even if they are not rusted up as badly
as these are. Will have to think on this for a bit.
Pictures not taken as greasy hands and camera should not mix. Will set up
and pose photos later.
Washed grease and grime off crankcase...BAD news...crack/break in neck of casting
around uppper bearings...scrap. Pressed crankshaft out without bothering to
remove rod caps to salvage brass reed block...that finished breaking crankcase
as rods even broken ones will not clear. My collection of brass reed blocks
increases by one...each represents a powerhead problem...usually a bad crankshaft
For some reason I have no extra crankcases and I have only broken 2.
Not much in way of salvage from this powerhead despite high hopes.
Another learning experience.
The project overall will not suffer but for time and effort expended on power head cylinder a zero. Sometimes no matter how well you play the game you still
I have a Mercury KF7 crankcase in oven at 500 degrees. Despite prior washing
resdue oil stink. Made up quick batch of muffins to cover up using kitchen
stove for outboard work. The eagle eye and nose are due back shortly. I hoped
heat would make bearing drop out...no such luck.
Tried to clean up cylinders from stuck powerhead with hone...top of cylinder shined up but hone could not break thru corrosion at lower end of cylinders. No great surprise. Sprayed pistons with PB Blaster rings still stuck. No great loss there either.
After a few days of lawn and leaf duty I got in an hour or so of basement
shop time. Honed the cylinders of spare powerhead...they cleaned up nicely.
The clamp assembly had a weld repair and the screws were rusted and one
was bent. An excellent clamp casting available lacking screws. Used Dremel tool
and abrasive disc to cut slots in aluminum then used hammer and chisel to
split out an opening to work the screws out. Some careful work with press
may make screw close enough to straight to work. Discs will be removed and
reinstlled using the Mercury Service Tool for that job. There are several
work around techniques if that does not work as advertised.
Although the spare powerhead appears good to go it will be taken apart to
check bearings, seals, crankshaft and reeds. No point in finding out later
that it should have been done while the doing was easy. Hopefully no
unexpected bad news.
The bearing stuck in KF7 crankcase came out after making a close fitting plug
on lathe to catch the very narrow edge of bearing....into the press and
cautiously pump up pressure...a little bit beyond what I thought was
wise...BANG!!! Both bearing and plug came out leaving a corroded spot where
bearing had been. I do not know if crankcase is reusable but experience