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Aligning engine to shaft(13 hp yanmar 2gmf on sailboat)



 
 
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  #11  
Old October 20th 08, 04:56 PM posted to rec.boats
Jim
external usenet poster
 
Posts: 1,044
Default Aligning engine to shaft(13 hp yanmar 2gmf on sailboat)

wrote:
On Oct 20, 10:50 am, jim wrote:
wrote:
On Oct 19, 10:42 pm, jim wrote:
wrote:
On Oct 19, 10:16 pm, jim wrote:
wrote:
On Oct 19, 6:33 pm, "mmc" wrote:
wrote in message
...
Years ago when I installed this diesel in my sailboat, I read about
aligning the engine output shaft with the prop shaft by using a valve
clearance guage to check all round the round pieces that bolt the two
together. One would tighten or loosen the engine mounts to make it
the same all round. I can no longer find these directions and am
having problems getting it just right. One side is off by .008" and
all I can think of is slightly rotating the engine (about a vertical
axis) by pushing against the engine mounts but this doesnt sound
right. Thoughts?
DB,
You're doing it right. I couldn't remember the tolerance so did a google on
aligning sailboat engine and found this on a site (
http://www.alberg30.org/maintenance/...n/Diesel/Insta...)
about swapping an Atomic 4 for a diesel:
The most critical part of an engine replacement is the new engine alignment
with the prop shaft. The tolerance on this is .004" maximum. This
measurement is taken between the engine flange and the shaft flange. It is
in two planes, vertical and horizontal.
If you can't get that close you probably need shims.
mmc, thanks. I was considering living with my .008" diff but I'll
give it another try.
However, I think the height and horizontal adjustment are dead on.
Unfortunatly, the plane of the engine output flange is misaligned by
roughly .3 degrees (three tenths of a degree). I got this number by
taking the size of the gap between the two flanges (.008) divided by
the radius of the flange and taking the arc tan. I really think I
should use the diameter of the flange which would give me .15 degree.
Is this close enough?
The bolts slide in very easily indicating good alignment.
Take your time and do it right. I wouldn't settle for more than .002
difference top to bottom or left to right. Also you want to rotate the
engine and prop shaft 90 degrees and check again after you think you
have it right. You will be rewarded with a lot less noise and vibration.
I will do so. This necessitates taking apart part of the bulkhead
around the engine compartment but it is intended to be taken apart.
Then, I get a large crowbar and brace it against the engine mount
whilst I pound on it to slowly shift the front of the engine. At
least its no longer 100 degrees down below.
Gentlemen do not pound on engines. Can't you get at the mounts to loosen
them you can adjust them or move the motor?
Mounts are each held to the mahoganey stringers with 2 lag bolts. The
mounts have elongated holes. In theory, you could loosen the lag
bolts and somehow lever the engine sideways. In reality, the easiest
way considering the lack of room is to place the end of the crowbar
against the base of the mount and tap the other end of the crowbar to
nudge the engine over. Considering the length of the engine and
diameter of the flange and the gap of .008 at the side of the flange,
I figure i need to move the forward end of the engine toward port by .
1".

That's easy enough to work out. The coupler diameter is what? what is
the distance between the mating face of the coupler transmission end to
the centerline between the front engine mounts?


Jim:

That is how I came up with the .1".


Oops. I didn't see .1 inch I saw 1 inch
I guessed at 4" flange diameter and 34" span coupler to engine mount and
came up with 1/16 inch. I still think you need to loosen the engine
mounts. Sometimes the hard way turns out to be the easy way.
Ads
  #14  
Old October 23rd 08, 01:03 AM posted to rec.boats
IanM
external usenet poster
 
Posts: 60
Default Aligning engine to shaft(13 hp yanmar 2gmf on sailboat)

wrote:
On Oct 20, 10:50 am, jim wrote:

wrote:

On Oct 19, 10:42 pm, jim wrote:

wrote:

On Oct 19, 10:16 pm, jim wrote:

wrote:

On Oct 19, 6:33 pm, "mmc" wrote:

wrote in message
...

Years ago when I installed this diesel in my sailboat, I read about
aligning the engine output shaft with the prop shaft by using a valve
clearance guage to check all round the round pieces that bolt the two
together. One would tighten or loosen the engine mounts to make it
the same all round. I can no longer find these directions and am
having problems getting it just right. One side is off by .008" and
all I can think of is slightly rotating the engine (about a vertical
axis) by pushing against the engine mounts but this doesnt sound
right. Thoughts?

DB,
You're doing it right. I couldn't remember the tolerance so did a google on
aligning sailboat engine and found this on a site (
http://www.alberg30.org/maintenance/...n/Diesel/Insta...)
about swapping an Atomic 4 for a diesel:
The most critical part of an engine replacement is the new engine alignment
with the prop shaft. The tolerance on this is .004" maximum. This
measurement is taken between the engine flange and the shaft flange. It is
in two planes, vertical and horizontal.
If you can't get that close you probably need shims.

mmc, thanks. I was considering living with my .008" diff but I'll
give it another try.
However, I think the height and horizontal adjustment are dead on.
Unfortunatly, the plane of the engine output flange is misaligned by
roughly .3 degrees (three tenths of a degree). I got this number by
taking the size of the gap between the two flanges (.008) divided by
the radius of the flange and taking the arc tan. I really think I
should use the diameter of the flange which would give me .15 degree.
Is this close enough?
The bolts slide in very easily indicating good alignment.

Take your time and do it right. I wouldn't settle for more than .002
difference top to bottom or left to right. Also you want to rotate the
engine and prop shaft 90 degrees and check again after you think you
have it right. You will be rewarded with a lot less noise and vibration.

I will do so. This necessitates taking apart part of the bulkhead
around the engine compartment but it is intended to be taken apart.
Then, I get a large crowbar and brace it against the engine mount
whilst I pound on it to slowly shift the front of the engine. At
least its no longer 100 degrees down below.

Gentlemen do not pound on engines. Can't you get at the mounts to loosen
them you can adjust them or move the motor?


Mounts are each held to the mahoganey stringers with 2 lag bolts. The
mounts have elongated holes. In theory, you could loosen the lag
bolts and somehow lever the engine sideways. In reality, the easiest
way considering the lack of room is to place the end of the crowbar
against the base of the mount and tap the other end of the crowbar to
nudge the engine over. Considering the length of the engine and
diameter of the flange and the gap of .008 at the side of the flange,
I figure i need to move the forward end of the engine toward port by .
1".


That's easy enough to work out. The coupler diameter is what? what is
the distance between the mating face of the coupler transmission end to
the centerline between the front engine mounts?



Jim:

That is how I came up with the .1".


You will find it is extremely difficult to pry the engine sideways by a
small measured amount. When you do, you are laterally stressing all the
other mounts so you end up having to slacken one side at a time and rock
the engine on its mounts to let them settle into place otherwise you'll
lock in a permanent strain that will shorten the life of the mounts.
This is *NOT* a precision process and will be very frustrating.

It took about a day of cursing, prying and measuring to get the lateral
alignment on my 1GM10 good enough. My life was complicated by the fact
I had replaced the stern tube and mid shaft bearing so I was effectively
trying to get five points onto the same streight line :-)

The builder had *NOT* done a precision job of fitting the engine beds
(one bed was off 'level' relative to the shaft by 1" fore and aft) and I
was using slightly shorter aftermarket mounts so I had to rebuild the
beds so could not use the old mount positions for initial alignment. I
got round that and refitting the stern tube by making a template of the
engine that had the mounting brackets and a laser in line with the
output shaft coupling. That got everything close enough to be within
range of the mounts adjustment.

If you have a long shaft, dont forget to support it near the coupling.
You need to provide an upward force equal to the weight of the half
coupling and half the weight of the unsupported length of shaft, which
is most eaily done with some light line and either a pully and some
weights or a spring balance.

If you haven't allready got a flexable coupling consider fitting one.
I fitted one from R&D Marine http://www.randdmarine.com which
tolerates up to 10 thou misalignment between the coupling halves. I
shot for 1/3 of that, figuring that I'd need some margin for the mounts
settling. Alignment has remained well within spec all season and I've
quit worrying about it.
 




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