Re: [OMC-Boats] OMC Stringer trim

From: Gregory B. Fell <gfell@...>
Date: Tue, 24 Jun 2008 12:58:37 -0500
I have a 1969 Sportsman 155.  Regarding the hydrofoil mentioned by Lee, I installed this one a couple of years ago .  I noticed two significant improvements -- 1) the time to get on plane was drastically reduced.  As I like to ski, this was good.  2) cavitation in a high speed sharp turn was reduced.  Top end speed is supposedly reduced; but, since I don't cruise in the red RPMs, that was a worthy sacrifice.

Gregory B. Fell
The Fell Law Firm
3300 Oak Lawn Avenue, Suite 700
Dallas, Texas 75219
PHN: 972-488-8177
FAX: 214-219-4218

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MCKEOWN wrote:
Great information, Lee, thanks a million. My companion did suggest the "slow down" option a number of times, but that didn't seem too desirable to me! I think I may investigate the trim tab addition, as that seems like a fairly easy solution to getting some degree of trim. 

There appears to be some degree of adjustability in the front engine mount. Has anyone tried to re-trim using this feature? I know from past experience that sometimes a very small change in thrust angle makes a big difference in boat dynamics.

You mentioned an under-floor water issue. I shipped a fair amount of water during several hours (maybe 20 gallons?) not sure where it came from, but the bilge pump wasn't working and a lot came out the plug at end of day. There seems to be a small opening at the bottom front of the bilge. Can water get into the foam through that opening? Is that harmful to the foam or the boat structure? Has anyone attempted to seal said opening? I assume it's nice to give water a way out if it should get into that space, but it'd be nice if bilge water didn't get in there.
One other thought on that water in the boat. I just noticed that the blower outlet is right at the beltline, behind a piece of trim. It seems that following seas could likely get that high and admit a fair amount of water. Has anybody else seen this as a problem?

I need one of the forward-facing aluminum vent scoops for my boat, the ones maybe 1-1/2" tall, 5" wide, and 10" long. Does anybody have one of these?


Hi Bob,
Good to hear about your experiences. I have a 16-ft Evinrude Sportsman
(a similar hull configuration to yours) and can offer my
"for-what-they-are worth" observations:
1) Be thankful you have the last hull design OMC released in 1970. It
incorporated a 4-inch deeper dead rise by extending the keel over
earlier (1964 - 1968) versions of the same 16-foot Johnson and Evinrude
hulls. You boat may have the new-for-1970 water ballast tank under the
floor. Check to see if you are carrying any excess under-floor water
(weight).  The rougher ride is Gull-Wing the trade-off for better
stability. Deep Vee's are better at cutting thru the rougher stuff but
are less stable and can be susceptible to chine-walking (lateral
movement underway). Yeah, my better half always complains, "can't we
slow down?"  Especially rough are the seats the closer to bow you get,
where the up/down motion is more pronounced.
2) The propensity to porpoise is also pretty common on these boats.
There are some cures -- some more practical than others:

a) Back off the throttle and slow the boat down, to the point of
stopping the unwanted oscillations.

b) Add electric or hydraulic transom mounted trim tabs that allow you to
adjust the attitude for load, speed and see conditions. Does your boat
have the small, aluminum fixed tabs? 

c) some people have reported adding a hydro-foil on the sterndrive's
anti-cavitations plate, reduces proposing (personally haven't tried

d) Do everything possible to lighten the aft-end of the boat. I won't
suggest practical ways to this but anything you have back there
contributes to the problem.  

Lastly, DO NOT TRIM out the STRINGER outdrive. Many people sadly did.
The balls gears were not designed or intended to drive a raised lower
leg under power except for minimal, shallow water use, at idling speed,
(and even then I hate to even do that). To overcome the power trim
limitation OMC eventually added a hydraulically driven jack lift under
the lower front engine mounts. These were primarily offered on the
short-leg Ford V8's and the inline Chevy's. I think retrofitting one
under a GM V-series (Buick V6-V8 or Small Block Chevy V-8) would prove
to be difficult and not very useful. If you go the transom-mounted
movable trim tab rout, be sure and check that you boat's transom is
reinforced, as it can generate some serious forces and some of these
boats had very thin transoms.
Lee Shuster 
Salt Lake City

From: omc-boats-bounces@...
[mailto:omc-boats-bounces@...] On Behalf Of mckeown
Sent: Monday, June 23, 2008 10:18 AM
To: omc-boats@...
Subject: [OMC-Boats] OMC Stringer trim question

I finally got my '71 Chris Craft Gull Wing 155 out yesterday after
owning it for about a year and  a half! Fun boat, but it seems to ride
pretty rough on choppy water. Cheatham Lake (Cumberland River through
Nashville) where I was riding has heavy boat and barge traffic. We were
constantly pounded by wakes, even from small boats, and swells behind
the bigger boats. My companion, new to boating, wasn't too wild about
the ride.


The boat seems to porpoise readily on fairly minor swells. The normal
solution to this problem is to change the thrust angle by adjusting the
position of the stern drive in. Can you make this sort of adjustment
with the Stringer outdrive?


I discovered one unexpected advantage to owning a vintage boat - I
seemed invisible to the TWRA boat police. I think they figure that an
old fart like me in an old boat probably knows enough to have the right


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Received on Tuesday, 24 June 2008

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