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Author Topic:   OMC 60-degree motors?
peteinsf posted 05-30-2002 04:34 PM ET (US)   Profile for peteinsf  
When did OMC switch to the 60 deg block on the V4 and V6s? (I can hear Larry now, "when Merc's patent ran out")


george nagy posted 05-30-2002 04:49 PM ET (US)     Profile for george nagy  Send Email to george nagy     
peteinsf posted 05-30-2002 08:05 PM ET (US)     Profile for peteinsf    
Is it only the 150 and the 175? I thought all the V4 & V6 models were 60s now...
triblet posted 05-30-2002 08:37 PM ET (US)     Profile for triblet  Send Email to triblet     
My 96ish 90HP Evenrude is a 60 degree V4.

60 degree V6s are inherantly dynamically balanced.
90 degree V6s are NOT.
IIRC, NO V4 is inherantly dynamically balanced.

This would explain why OMC did it. What I
can't understand is why they ever made a
90 degree V6. Unless they started with 90
degree V4s, and then started building V6s
on the same tooling. This is why Detroit
built a lot of 90 degree V6s -- use the same
tooling as 90 degree V8s (which are dyn.


peteinsf posted 05-30-2002 10:32 PM ET (US)     Profile for peteinsf    

The insides of 1985+ 90 deg motors are for the most part exactly the same. Kinda like ice-cream scoops. You pick "4cyl, 6cyl or 8cyl"

The factory service manual covers all of the loop charged motors (120,140,200,225,275 & 300) in one book.

In funny you bring up the balance thing since all of these motors came out when the V8 (that bombed) came out, I guess they were betting the farm on the V8. Merc got it right the demand was V6s...


peteinsf posted 05-30-2002 10:32 PM ET (US)     Profile for peteinsf    
Sorry "It's funny..."
lhg posted 05-31-2002 01:14 PM ET (US)     Profile for lhg    
Thanks to Chuck's info, I guess we now know why the 2.4 litre Merc V-6's, introduced in 1976, quickly took over the go-fast, racing and bass boat markets in the 150-200HP range, even though they had the smallest displacement. Yamaha's V-6's are also 90 degrees, copied from OMC.

Mercury tried a 76 degree V-6 (275HP), also copied by Yamaha for their 225/250's and HPDI's, and it turned out to be a dog for some reason. Maybe this balance issue again? They quickly corrected this with the 3.0 litre 60 degree 225/250/300HP engines, fastest in their categories compared to other's 76 and 90 degree engines.

Chuck's post also perhaps explains why Mercury/Carl Keikhaefer never built a V-4, instead opting for the in-line six, which also is inherantly balanced, I believe.
Maybe Whaler's parent company deserves more engineering credit that it has been getting around here lately!

jimh posted 05-31-2002 05:46 PM ET (US)     Profile for jimh  Send Email to jimh     
I think the GM 5.7L V-8 block had two cylinders lopped off to become the 4.3L V-6. Automotive engineers might have more of that story to tell.
triblet posted 05-31-2002 11:56 PM ET (US)     Profile for triblet  Send Email to triblet     
Yes, inline sixes are inherantly dynamically
balanced. As are (none on outboards) V12s
(effectively two inline sixes), straight 12s
(again, two inline sixes), 90 degree V16s
(two 90 degree V8s),
etc. Straight twos, threes, fours are not.
V2s are not, in spades, which, along with the
uneven ehaust pulses, accounts for
the Harley LUMPA, LUMPA, LUMPA sound.
(Linda, load the sound seeking Stinger. ;-).
Don't remember about flat fours and flat


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