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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Motor Mount Measurement...

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ClamBeach
Master Marine Consultant

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3072 Posts

Initially Posted - 03/06/2003 : 15:49:44

I have a new Garhauer motor mount in hand and am ready to bolt it onto the vessel. (The engine is a Honda 8hp longshaft)

For those of you who have this mount, and have access to your boats, what is the approximate distance you have from transom (under the lip) to the top of the mount base ? (assuming you're happy with the lash-up)

I was going to mount at the same level as the older aluminum bar mount. (reusing 2 of the holes). Seems about right but... any practical advice would be appreciated.

Currently maintaining two holes in the water...'77 Venture 23 and new to the family,
'78 Catalina 25

Edited by - on

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 03/06/2003 : 18:00:46

ClamBeach,

I don't have either a Honda 8HP long shaft, or a Garhauer motor mount. I have a Yamaha 9.9HP high thrust extra long shaft motor on a Garelick 20HP mount. However, I'm not one to let that discourage me from trying to answer your question.<img src=icon_smile_big.gif border=0 align=middle>

On my 1979 C-25, the top of the motor board is 9-1/2" below the bottom of the aluminum rub rail. That's at the centerline of the motor with the motor mount in its lowest position, boat approx. level on trailer. My motor has a 25" leg (cavitation plate to top of motorboard). In other words, the top of my prop is almost 3' below the rub rail. This geometry gets the prop deep enough under most wave conditions, without coming anywhere near dipping the powerhead.

The only time I've had the prop suck enough air to rev up badly was when running an ocean inlet with tidal current against the wind and 3' to 4' choppy waves. For a short distance at the breakwater, there was a lot of hobby horsing going on.

-- Leon Sisson

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 03/06/2003 : 18:28:18

"For those of you who have this mount...what is the approximate distance you have from transom to the top of the mount base?..."

This would depend on the motor mount travel distance and shaft length of the motor that is being used. You should probably determine the optimum prop depth of your outboard, then install the motor mount so this depth is acheived when the mount is in the down position.

<img src="http://www.catalina25-250.org/c25sm.gif" border=0>Don Lucier<img src="http://www.catalina25-250.org/c25sm.gif" border=0>
<img src="http://im1.shutterfly.com/procserv/47b2cc32b3127cce92e981259d130000001010" border=0>
North Star SR/FK

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 03/06/2003 : 21:45:09

Expanding on Don's reply, the long shaft Honda's cavitation plate is 22" below the top of the mounting board. To minimize cavitation, I suggest putting the anticavitation plate of the motor at least 3" below the static waterline. (With the extra-long shaft, I'd say 6", but with a long shaft, the mounting board would drag in the waves.) That suggests that the top of the mounting board, with the bracket in the down position, should be at most 19" above the waterline. If you feel comfortable putting it lower, fine.

At that level, I'd check for clearance for tilting the motor with the bracket up. There's nothing wrong with blocking the bracket away from the transom a little--in fact, I recommend using at least a 1/2" sheet of Starboard--thicker if you need the clearance--to spread the load on the fiberglass. If you haven't worked with Starboard, it cuts and shapes like wood, if not easier.

My P.O. mounted his new bracket where the old one was, which put the anticavitation plate of the long-shaft Honda right at the waterline--a big mistake. Under way, it squatted a little, but waves would cause lots of screaming. Also, when I walked forward with the motor idling, it would suck air into the cooling intake. Not good. Base your measurements on the waterline, not the rub rail.

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

Edited by - dave bristle on 03/06/2003 21:46:33

Edited by - on

frank
Deckhand

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USA
2 Posts

Response Posted - 03/09/2003 : 21:49:48

CLAMBEACH
I installed a Garhauer mtr mt with a 17 in drop
last year. Then hung a 8hp honda high thrust motor
long shaft(22"I think) on it. I used the original
mounting holes and put a 3/4" plywood back plate
on inside. With the motor lowered & going 1/2
throttle the mounting board is just above the
water. The board is in the water when going any
faster. When I first installed the new motor &
mount I could barely pull the motor up, then I met
a "MR GARHAUER" at the Annapolis boat show and
told him my problem, he said just back off the
through bolts a 1/4 turn and that should help,
IT DID. The new Garhauer motor mts should lift
70lbs he said. I'm happy with my new toys.

Also last spring I replaced the Sw.keel cable,
winch,pivot pin,shoes using the threaded rods
trick I learned about here. In addition to the
rods I used a bottle jack and a just in case
bracket which would keep the keel from tilting
sideways.

1st timer who has learned a lot from all who ask
and answer. thanks
Frank Law
"About Time" Cat. 25 sw. keel ,std rig.

Frank Law

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 03/09/2003 : 23:37:42

Frank,

Welcome aboard. It's..."About Time"! <img src=icon_smile_big.gif border=0 align=middle>

<img src="http://www.catalina25-250.org/c25sm.gif" border=0>Don Lucier<img src="http://www.catalina25-250.org/c25sm.gif" border=0>
<img src="http://im1.shutterfly.com/procserv/47b2cc32b3127cce92e981259d130000001010" border=0>
North Star SR/FK

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 03/10/2003 : 09:43:47

Thanks to all for the feedback... From Franks' response it sounds like I'd better be careful not to get things too low.

Been down with a nasty flu.. haven't fiddled with either boat in 2 weeks. :>(

-- CB

Currently maintaining two holes in the water...'77 Venture 23 and new to the family,
'78 Catalina 25

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 03/10/2003 : 19:39:37

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
...When I first installed the new motor &
mount I could barely pull the motor up, then I met
a "MR GARHAUER" at the Annapolis boat show and
told him my problem, he said just back off the
through bolts a 1/4 turn and that should help,
IT DID....
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>
Hi Frank... Was that the bolts through the transom, or the bolts holding the cross-tubes to the transom mounts? If the former, I'm curious about the cause--unless it has to do the the curve of the transom causing the bracket's hinge-points to bind somehow.

Glad it worked...

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

Edited by - on

frank
Deckhand

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USA
2 Posts

Response Posted - 03/18/2003 : 21:45:11

In response to Daves question ,the bolts were thru
the mtr.mount tubes not the transom. Sorry for the slow reply
Frank Law

Frank Law

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 03/20/2003 : 09:04:46

Here is the easiest way to install the motor mount. Measure from the inside lip of the motor mounting area to the cavitation plate (skeg)

See below:

<img src="http://im1.shutterfly.com/procserv/47b3dd01b3127cce9521b8c953840000001610" border=0>

Duct tape a yard stick so that the measurement (say 22 inches) sits at the very top of the motor bracket.

<img src="http://im1.shutterfly.com/procserv/47b3dd01b3127cce9521bd4f13980000001610" border=0>

Then with the bracket in the down position, find out where the bracket has to sit so that the bottom of the yardstick is about one inche below the waterline. (if you are not sure where this is, the bottom paint is roughly at the waterline area...Compare to where the bottom paint ends on your rudder)

dw

D. Wolff - "The Flying Wasp" #401 sr/sk
Chief Measurer C-25/250 National Assn.
<img src="http://www.flags.com/dreamimages/Flags/measurer.jpg" border=0>

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.