August 25, 1961
Bulletin No. SB-863
Trouble Shooting
SUBJECT: Overheating V-75 engines;
75 h.p. V4S-12 thru V4AL-13F.
We have received reports that some V-75 engines would overheat after prolonged low to
medium speed operation. Extensive investigation and experimentation revealed this
could occur on some engines by exhaust gas leaking through the split in lockwasher #307708
under the rear gearcase stud nut, and then into the cooling system.
FIGURE 1
As a result the split lockwasher has been
replaced with a flat washer, #552993, to
solve the foregoing possibility. The
illustrated elastic stop nut must also be
used with this washer to provide the
required locking power. Failure to do so
will invariably result in loose gearcases
which in turn can later cause extensive
gearcase damage. Under no circumstances
must the old shoulder nut be installed
with the flat washer.
Figure 2 illustrates the flat washer and
elastic stop nut installed on the studs of
a V-75 gearcase. Because it is extremely
difficult to determine when exhaust gases
are definitely leaking past the lockwasher
on the rear gearcase stud, we recommend
installing these flat washers and elastic
stop nuts whenever the gearcase is removed
for any reason to insure against the
possibility of this difficulty occurring
in the future. They should definitely be
installed on engines which are overheating
as well as checking the points contained
in Service Bulletin #SB-796. Torque studs
to 24 ft. lbs., nuts to 18 ft. lbs.
FIGURE 2.
The new washer and nut is available
through the parts distributors. Since
both nut and washer are made of special
stainless steel to resist corrosion in
salt water areas, substitute washers and
nuts must not be installed. List price
of nut 307160 is $.60 each, washer
552993 is $.05 each. Both prices are
subject to standard parts discount.
(over)
