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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Installing Motor Mount

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dnorth
1st Mate

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USA
36 Posts

Initially Posted - 10/11/2006 : 21:17:19

I have a new Garhauer motor mount but the holes don't match the holes for the old motor mount. I am planing to use a piece of 1/2" starbord between the mount and the transom. So,

1) Do I need to fill the old holes? If so with what?

2) Is there anyting special I need to do to drill the new holes?

3) Is there anyting special about the bolts I should use to attach the mount to the transom.

4) How do I attach the starbord to the transom?

Any ideas would be helpful.

David North
Catalina 25, Swing Keel, 1977, Hull #6
Edmond, Oklahoma

Edited by - dnorth on 10/11/2006 22:08:52

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 10/11/2006 : 21:35:02

Hi David... I suspect your original bracket was an aluminum Fulton that had closely spaced flat bars from the transom to the motor mount... ? I've seen that on some early C-25s. Later ones used Garhauer brackets that do use the same holes as their new version.

Hopefully the Garhauer has square holes for the mounting bolts--that means you can use SS "carriage bolts" with domed heads and square sections under the heads. That way you can tighten the nuts from the inside without having to hold the bolt heads on the outside.

For the holes, I'd fill them with something--even if only some of the same caulk you use for the rest of the insulation. A slightly more professional approach would be Marine Tex.

I mounted the Starboard plate just using some Life Caulk and the bracket bolts. I put the caulk around each of the bolt holes, and also around the underside of the board just inside its perimeter, so a little would squeeze out all around when I tightened the bolts. My board extended down almost to the waterline and was cut to match the side of the transom (sort of). That's because the real inward pressure against the hull is at the bottom of the bracket--the top pulls out. Also it's the top bolts that you want to back well inside the hull.

Now, I was mounting it for a 110# high-thrust Honda, so I was purposefully overdoing it... Any size board is better than just putting the bracket against the fiberglass.

It's all pretty easy!

Edited by - Dave Bristle on 10/11/2006 21:47:15

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 10/11/2006 : 21:41:58

Never mind about the square holes and carriage bolts... I just looked at a pic of the bracket. Guess it'll be a 2-person job. I was able to rig my new aluminum Fulton alone, but that was by filing the round holes to make them square.

BTW, like any other hardware you bed with caulk, finger-tighten it till it's barely snug and let the caulk set for a day or two, and then crank down the nuts. That way the caulk makes a nicely compressed gasket.

Edited by - Dave Bristle on 10/11/2006 21:45:54

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 10/11/2006 : 22:13:10

"1) Do I need to fill the old holes? If so with what?"

I'd just use the same marine bedding compound you'll use under the backing plate. Squeeze a little in the holes when you attach the backing. It's likely nobody will see the holes again for a looong time.

"2) Is there anything special I need to do to drill the new holes?"

I use brad point bits (wood). Putting a short piece of masking tape over the 'drill site' and drilling through it will produce a cleaner edge and reduce gelcoat chipping.

"3) Is there anyting special about the bolts I should us to attach the mount to the transom."

Good quality 316 stainless. Be sure to lube the threads before tightening... if you've ever had stainless threads gall up and seize you'll know why. Use large stainless 'fender' washers under the nuts on the inside of the boat... or other backing material to distribute the load. Nylon locking nuts or lockwashers are a must.

"4) How do I attach the starbord to the transom?"

Use 3M-101, Lifeseal or Sikkaflex (etc) to 'bed' the starboard at the same time you bolt the mount on. The same bolts that hold the mount will hold it in place. Note the advice above on just going 'snug' (pushing a nice bead out all around the edges)... then letting the bedding compound harden up before final tightening. Figuring out how much bedding to apply, how much to squeeze out and how to dress the edges of the caulking to look pretty is an acquired skill.

For a water-based caulk, dipping a finger in some dishsoap is helpful. For petrol based caulking, a spritzing of WD-40 or a dip of diesel on the fingertip helps. Have plenty of rags handy.

Be sure to radius (round) the corners of your backing material... (whatever you use). Rounding the corners distributes stress and reduces the chances of gelcoat cracks forming. I made my backing an inch or two larger than the motor mount base in all directions.

Edited by - on

dnorth
1st Mate

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USA
36 Posts

Response Posted - 10/12/2006 : 11:28:23

Thanks for the great instructions.

Do I need to treat the new holes in any special way before I put the bolts in?

Do I need to put any seal on the inside after the bolts are attached?

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 10/12/2006 : 12:07:26

Treat the holes? Not in my opinion... My transom had a dense foam core, so if any moisture eventually found its way through the caulk, it shouldn't matter much.

Seal inside? No need.

BTW, speaking of the foam... When I drilled into the transom, the instant the drill got through the first layer of glass and hit the foam, it almost pulled out of my hands! If you have a variable-speed drill, go slowly to minimize the surprise.

Edited by - on

sweetcraft
Admiral

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USA
816 Posts

Response Posted - 10/13/2006 : 01:40:25

I used the great instuctions for my mount for the Honda and it is sure a success, no problems since installation. For filling the extra holes I used a plug cutter, 3/8 ", from the Starboard scrap and with 3M 101 tapped them flush. Let us know how it goes together.

Edited by - on

dnorth
1st Mate

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USA
36 Posts

Response Posted - 10/21/2006 : 18:55:13

I need to determine the correct location for the mount. I have a long shaft motor (25"). So It seems that I should put the mount so that when it is down the top of where the motor attaches is 25" from the water. Does that sound correct? Does it matter how much the shaft goes into the water?

The original old mount (aluminum Fulton that had closely spaced flat bars) is moutned lower than were it seems I will need to put the new mount.

Edited by - dnorth on 10/21/2006 21:08:32

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 10/21/2006 : 21:29:00

I mounted my XL shaft Honda so the anti-ventilation plate (the flat plate above the propeller) is about 4" below the painted waterline in the 'upper' down position. (With a new style Garhauer mount). In the 'bottom' down position the prop is a lot deeper. [C25's tend to squat under power]

I use the "upper down" notch for running in flat water. I use the the 'full down' position for docking, motor sailing, rough water and when I want to go forward to the bow without the engine sucking air.

You can measure from the plate to the 'mounting notch' and set the motor mount accordingly.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 10/21/2006 : 22:20:38

this is a picture to give you some visual cues, I will give you measurements tomorrow, also it is designed to have the bolts come through at the back wall of the shelf in the quarterberth.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 10/22/2006 : 15:49:53

The 89 transom height is different so I am not sure where to measure from, however, as I said before the shelf area in the quarterberth really determined it for me, the bottom two bolts go through with just enough room for a small fender washer and the top ones work out fine. Note my bracket is bolted in the bottom holes so the motor would not be too low in the water on the second notch, any lower and the second (low) setting would have been worthless for me.

Edited by - on

dnorth
1st Mate

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USA
36 Posts

Response Posted - 10/22/2006 : 19:25:59

Thanks for the picture. It was helpful.

How far is it from the top fo the mounting plate (plate with the hole for screws) to the water?

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 10/23/2006 : 12:04:36

I think someone else with the same transom should give you measurements but as I said above, it is the shelf in the quarterberth that determines the holes in the boat for me.

Edited by - on

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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.