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  Adding CMC trim to 13' with 20hp Yamaha

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Author Topic:   Adding CMC trim to 13' with 20hp Yamaha
tjxtreme posted 08-13-2010 11:57 AM ET (US)   Profile for tjxtreme  
Hi all, I have a CMC PT 35 I am considering adding to my 13 foot Whaler. I am currently running a 2007 Yamaha 4 stroke 20 hp (~135 lbs I think). The CMC would add about 40 lbs to the transom and about 6" of setback.

I am satisfied with the power of my current setup, but tired of messing with the manual tilt when trying to fish. There are a number of performance variables that will change if I add this, and I am looking for input.

-Increased weight at the stern: slower? Too heavy?
-Increased setback: better performance? More strain on transom?
-Trim underway: more efficient use of motor?

This thread raised some concerns
http://continuouswave.com/ubb/Forum3/HTML/009926.html

thegage posted 08-13-2010 12:20 PM ET (US)     Profile for thegage  Send Email to thegage     
What year Whaler? Notched transom or not?

I have a '69 13-Sport on which I have mounted a long-shaft E-TEC 30 (manual tilt). I used the Kentfab Transdapter to raise and strengthen the transom, then a CMC manual jack plate (4" setback) to get the engine to the right height. Total weight is about 185 lbs.

Certainly not too heavy for the boat; some owners are putting 40 hp 4-strokes on their 13s (200 lbs.+), but you may see some minor performance drop with the 20.

Yes, more transom strain, but if you are using a short shaft it is lower down so not so bad. I wanted to be certain in my set up.

As for trim and performance, it depends on how you use the boat. I use mine primarily for skiing/tubing with my kids, so I leave the engine tucked in a bit to force the bow down and get on plane quicker. When I fish with them, we don't go very far so top speed isn't critical. If I did worry more about that I would have power T&T as the trim rod holes always seem to fall in the wrong place for optimizing boat speed and porpoising.

John K.

tjxtreme posted 08-13-2010 12:23 PM ET (US)     Profile for tjxtreme    
Hull is 1978 so long shaft transom.

Thanks for the input.

Tohsgib posted 08-13-2010 12:39 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
No problem. I am running a 240lb Suzuki on my 81. I had a 182lb OMC 40 with the CMC PT130 on it for years which brought it up close to the 240 mark. The added height is great and PTnT is AWESOME. That boat will come alive, you will not regret it. You will be able to tuck it in even further so holeshot will be lightning fast, then trim it up. I normally find a spot where the hull lifts but not really porpoising and leave it be for the day. I know the PT35 is much lighter than the 130.
tjxtreme posted 08-13-2010 12:53 PM ET (US)     Profile for tjxtreme    
Cool, thanks... I'll get that baby on this weekend. For mounting, do I need to shim it out to account for the transom curvature or is it not an issue?

Tohsgib posted 08-15-2010 01:55 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Was not an issue on mine. The corners did not fit flush but 95% of it did. I just put a bead of silicone around it.
tjxtreme posted 08-16-2010 03:27 PM ET (US)     Profile for tjxtreme    
Got the CMC PT 35 mounted, after measuring about 20 times, and drilling once.

It actually took a few tries to find the center of the transom- the drain tubes and brass fittings are NOT a suitable reference (seemed to be at least .5" tolerance on their placement). It was a little painful to put four new large holes in the transom, but it was nice to see all the layers of wood (that were nice and dry).

As a side note, the transom side of the CMC trim unit deflected to the shape of the transom when I tightened the .5" bolts. I don't think it will cause the unit to bind, but I will be watching for that.

BobL posted 08-17-2010 12:35 AM ET (US)     Profile for BobL  Send Email to BobL     
tjxtreme,
Would you be willing to post some pictures of the CMC PT 35? I would like to see some of the mounting details. I will be installing a 25 hp Yamaha on my 13 Sport restoration project by the end of summer and I do not like the idea of drilling a new set of non-standard holes that do not allow for height adjustment. I think your solution sounds great and I would like to see what it looks like.
Thanks,
Bob L
Free Bird posted 08-20-2010 06:46 PM ET (US)     Profile for Free Bird  Send Email to Free Bird     
Add me to the list of members hoping to see pictures of your CMC lift. I am thinking of putting one on my short shaft '72 Whaler. My engine is a 2005 Johnson 25 shortshaft. I feel your anxiety over drilling into my newly perfected transom!
tjxtreme posted 08-25-2010 08:00 PM ET (US)     Profile for tjxtreme    

Here are pictures of my newly installed PT 35 on a 1978 13'.

Side view with motor
http://i1022.photobucket.com/albums/af349/tjxtreme/CMC%20PT%2035/photo7. jpg

Close up of mounting hole. There are three hex screws on each side (port and starboard) that hold the thick metal plate onto the CMC PT 35. The backup bolts for the motor lined up just enough to interfere (of course) with one of them, so we had to drill it out with a .5" bit and move the screw up an inch or so, drill/tap the hole, and screw back in the hex screw. I think this probably was not necessary, as the motor clamps and bolts will secure the metal plate.
http://i1022.photobucket.com/albums/af349/tjxtreme/CMC%20PT%2035/ photo10.jpg

Closeup of the mounting holes on the transom side. You can see the old motor mounting holes, I just filled with silicone so I can easily revert to the original setup. Also note how different my paint is from the original "tan" gelcoat around the hull number... it looks like dark grey compared to the paint.
http://i1022.photobucket.com/albums/af349/tjxtreme/CMC%20PT%2035/photo9. jpg


Any opinions on whether I should get a transom saver now with the extra weight and power trim? I have been previously storing and trailering with the motor clamped onto the rod at the outermost hole; the trailer axle is below the skeg.

Tohsgib posted 08-26-2010 08:22 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
If you can tow with the motor down or close to down you are fine. Transom savers are a joke in my opinion and may do more harm than good. If I had a flimsy built aluminum boat I might use one.

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