Re: [OMC-Boats] 1968 Evinrude Sportman 120

Let's assume that when you installed the Buick V6 as a replacement for
the Chevy II 120 hp Inline four that you left the original sterndrive
with it's upper gear case in place?
 
Let's also assume you are running at less than 1500 ft above sea level?
I'm asking these questions to verify the gear ratio which should be from
the original 120 hp inline four overall 1.61:1 running an upper gear set
of 19:20. The 155 hp Buicks came with upper gears of 25:25 yielding a
1.54:1 overall. This slight difference can be overcome with prop pitch
changes and isn't enough to worry about unless you are already running a
prop at the upper or lower pitch range (12" or 20"). The props that run
best are in the middle 13 (SST) to 17 (SST).
 
Any GM engine that was offered can be bolted up to the OMC intermediate
housing. This would include All 2-piece seal Chevy Small Blocks (V6 and
V8), Chevy Inlines, including the 153 (120 hp) and 181 (140) Chevy fours
and the 250 (165 hp) Chevy Six. You could also run the Buick 300/340
V8. All of these engines (with the exception of the Chevy V6) had the
old OMC log-style manifolds and will bolt up to your existing
intermediate housing with standard exhaust hoses.
 
If you changed out your intermediate housing to the 78 and newer
stringer you could accommodate the Chevy V6 (I've never tried this but I
think it is necessary to accommodate the 78 and newer manifolds which
have the upturned ends).
 
You will face additional challenges fitting the longer Straight Six (but
it's a nice running motor) and the V8's simply because on your 68
Sportsman the engine bulkhead is molded into part of the deck. On the 67
and earlier Sportsman's this bulkhead is removable and facilitates
installing the longer engines. View my website to see how I replaced a
1966 Buick V6 with the a 1971 small block Chevy V8 (OMC)
http://hhscott.com/evinrude/chevy_v8.htm
 
Bottom line: I'd go with another Buick V6 (the newer even-fire 231 will
substitute for the old odd-fire 225 --- sorry to hear about the rag in
the oil pan) or go with another inline 4 (120 or 140) and reuse your
existing manifolds.
 
Lee Shuster
Salt Lake City
 
 

________________________________

From: omc-boats-bounces@...
[mailto:omc-boats-bounces@...] On Behalf Of Ann Cousins
Sent: Monday, June 30, 2008 8:54 AM
To: omc-boats@...
Subject: [OMC-Boats] 1968 Evinrude Sportman 120

Hi...we own a 1968 Evinrude Sportsman 120 that needs a new engine.
About 5 years ago we installed a rebuilt 155 and it ran great for
awhile...and then not so well. Last week we tracked the problem down to
a rag left in the oil pan-the engine's cooked. We're now searching for
a replacement engine. The outdrive has a few years left, we think. Any
help or suggestions?

We're the original owners.

Thank you!

 
Received on Monday, 30 June 2008