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| Tony's Tips |
ARTICLE DATE: 10/01/2005 |
| Installing shafts, logs,
struts & rudders with your favorite engine / transmission |
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| Back to installing our crankshaft jig, getting out
the drawing and designing your front engine mounting "system". I used the
term "system" as there are so many options that each vessel might
require to make the engine package fit RIGHT. We have gone this far and
really need to think about the front mounting as a "system" and not just
something that the front of the engine sits on. Typical mistakes that are
made here is thinking that the engine brackets that came on the front of
the engine must be used. This could not be further from the truth.. In fact,
in probably 75% of the repowers we do, the front brackets that were supplied
by the engine manufacturer are wholly inadequate in design to allow what
we feel is a proper installation. They may or may not be at the best C~C
distance for this install. They are more than likely not at the height for
the install. And, they may not be in the best fore and aft position either.
Of course, the weak at heart, or less informed individual, may come back
and say "that's what was designed and you cannot modify it" - HORSE MANURE
- You either believe in your own work, or you shouldn't be doing it in the
first place. |
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| Mid
Mounts |
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| Redesigning front engine brackets to allow the best combination of fit and
best alignment to the structure of the individual vessel cannot be done
by the engine manufacturer on a drawing board 2000 miles away. Every vessel
is different. It's just about always easier to re-design the front brackets
than to re-design the boat. If the supplied front brackets happen to be
a good compromise as to their location and just happen to "fit" where they
should, then by all means, use them. |
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| Front
mount designed for non-symetrical stringers |
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| Clearance
for seawater pump removal |
Low
mount |
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| I'll mention a case in point here - Since the Cummins
B is a very popular engine used for repowers, I will mention that the standard
front mounts, although nicely made, interfere with the R&R of the seawater
pump in their normal position. By using a totally different front bracket,
or by adding a spacer behind them, of ¼" to ¾", you will accomplish at least
two things. One, you can increase your C~C distance from approx 22.5" to
something wider ( like 23-24" C~C). And now you will be able to R&R your
seawater pump without lifting the engine and removing the bracket first.
When we use this "stock" bracket, we like adding a ½" to ¾" spacer,
and increasing the bolt length accordingly. There are NO engineering issues
here as to loads, strengths, etc., as long as the new bolts chosen are of
a 8.8 or better quality, and things are put together right, and tight. |
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| Cummins
B universal front brackets |
Angled
mid mounts |
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| Universal
front mid-bracket |
Low
mount universal bracket |
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| Another important part of the front mounting
"system" that would be done now is whether you may have an additional belt
driven accessory, like a second alternator or hydraulic pump. This is best
done at this time as it usually can be designed as part of the front bracket
assembly. All accessory drives should be part of the engine so as to "move"
with it, and many times the only place to bolt heavy bracketing to an engine
is where the front mounting brackets are. The list of pictures here shows
just a few of the many types of modifications that needed to be made to
the factory front brackets to allow the proper fit in the vessel. |
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| Highly
modified C mount |
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| Jabsco
pump - C series |
Modified
QSM bracket to fit boat |
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| Finished
rails for a drop-in |
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| Shaft
jigging to old engine - trans package |
Jigging
up outside the boat |
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| Transmission
mounts to fit connect heigth |
Trans
mounts to fit connect width |
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| QSM
pedestals |
Mounts
and rails to fit |
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Well, by now we have made our decision as to front
bracketing, so now it's time for the stringer end of the front mounts. Again,
we prefer using aluminum extrusions whenever possible and "float" them in
the right place for perfect alignment-we then thru bolt as needed. We keep
a variety of Aluminum extrusions (6061-T6 structural angle) in stock and
we find that 4x6 thru 8x8 with thickness from 3/8" to 3/4" will cover 99+%
of all the install we've see. 12" long seems to always give more that enough
support while still allowing small adjustments in placement due to last
minute changes. Three to four well placed bolts from 3/8" to 1/2" diameter
with backing plates to spread loads over a wide area always keep things
secure.
If we look where we are now, you can see that the entire mounting system
and drive train was designed and built without lifting in the engine. Good
job. We had all that space to work and plan and we have far fewer bleeding
knuckles to prove it. |
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| New
rails front and rear mounts |
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| Finished
stringer bracketing |
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| Front
and rear mini rails designed to fit angle and width |
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| Trans-mounts
made to fit high stringers |
On
drugs |
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Installing
Shafts, Logs, Struts and Rudders along with your favorite Engine
and Transmission |
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