Long shaft motor on a 15" transom cmc pt35

[fishpoo]

Hello,
I'm working on a small 15' fiberglass skiff. I got a hold of a nice clean 1990 25 hp Mercury. My question is this is a long shaft motor and I have a short transom, I also got a used cmc pt 35 for $150.00 couldn't pass it up. Will I need to fashion a plate to raise this motor or can I install the pt35 higher to adjust for the additional 5" of length?
Thanks

 

[Chryslerman123]

I am in the same situation with a long shaft motor I want to put on a jon boat and I was told that I need a 20" transom.

 

[GA_Boater]

Hello,
I'm working on a small 15' fiberglass skiff. I got a hold of a nice clean 1990 25 hp Mercury. My question is this is a long shaft motor and I have a short transom, I also got a used cmc pt 35 for $150.00 couldn't pass it up. Will I need to fashion a plate to raise this motor or can I install the pt35 higher to adjust for the additional 5" of length?
Thanks

Before doing anything that will increase stress on the transom, you should make sure the transom is solid. Raising or adding 5 inches to the transom to mount the CMC will add stress and if the transom is not in good shape you may lose the motor. Simply raising the CMC 5 inches may not work.

You would be better served by finding a short shaft motor and then using the CMC if the new motor doesn't have tilt and trim.

I am in the same situation with a long shaft motor I want to put on a jon boat and I was told that I need a 20" transom.

Please start a new thread with more detail about the boat. This is fishpoo's thread and it never works when two people are looking for different answers in the same thread.

 

[jbcurt00]

Bonz and Jasoutside both have topics aboit long shaft motors on short transoms. Neither was happy w the results. IIRC, they used different methods to try to get it to work, and neither did.

 

[fishpoo]

GA boater the transom is in excellent condition. My thought was to design an aluminum plate to distribute the weight as well as raise the level of the motor, everything I read says that the cavitation plate should be level with the bottom of the boat. Is this correct or am I over simplifying this? I would assume that with the cnc added to the mix would help any minor issues of trimming the boat.

 

[ezmobee]

everything I read says that the cavitation plate should be level with the bottom of the boat. Is this correct or am I over simplifying this?

This is correct. However there's a formula (that I forget) they says for every X inches the motor is set back from the boat it can be raised X inches. So if your CMC unit sets the motor back a bit.....it's possible it may need to be raised even higher for optimal performance.

 

[Watermann]

I wouldn't go boring new holes in the CMC unit trying to get it raised up. I know the PT130 has 2 upper mounting holes that gives 1" of of variation in the mounting. The bottom has slots for the mounting bolts. Increasing the transom height is the correct way of making a long shaft motor work.

 

[Chryslerman123]

"Please start a new thread with more detail about the boat. This is fishpoo's thread and it never works when two people are looking for different answers in the same thread."[/QUOTE]

I worded my post incorrectly. I wasn't asking a question I was just informing him that He needed a 20" transom.

 

[fishpoo]

Ok so from what I understand and I've read regarding the pt35. The optimum position is 1.5" above the transom hence the "slotted holes". I believe this is to compensate for the 4" set back. So the pt35 really does nothing as far as elevating the motor. Long story short I guess I'll fabricate a small aluminum piece to slide over the existing transom, factoring in the increased set back and new height and distribute the weight across the transom for optimum support. As far as performance goes...lol...That will be determined later. As long as this is safe I can make adjustments later if needed. I'm just a man trying to catch a fish.lol

 

[fishpoo]

Side bar; I've been trying to share some photos, but it always says my pictures exceed the size limit. Anyone else have this issue?

 

[jbcurt00]

Photo posting help

http://forums.iboats.com/forum/forum-rules-and-guidelines/9938375-photo-upload-tutorial

I use, and recommend option 3, a 3rd party pix hosting site. I use photobucket, but there are others