15 hp on a Mac 25?

[Chip Giles]

Has anyone ever modified the transom (or heard of anyone who has) to put a 15 hp outboard on a MacGregor 25? Does the transom need to be beefed up to do so?

 

[Norman]

25 hp

My 1986 Mac25 had a 25hp 2-stroke 1984 Evinrude model on it when I bought it a few years ago. Not knowing better at the time, I used it as is, mounted to the standard transom mount with no modifications. I did a lot of motoring on the Sacramento Delta that first summer. Once I discovered my error, I replaced it with a 6hp. Upon inspecting for damage, all I found was the top 2 bolts that attach the transom mount to the transom were a little loose. I always kept it at low RPMs (hull speed could be reached at about quarter throttle, or less). I think anything over 10hp is a waste of gas and extra weight.

 

[Clayton Fawcett]

Mac 25 Motor Mount Modifications

The 1986 Mac 25 that I bought has a HEAVY Yamaha 9.9 4 Stroke with electric start. From all the dealers I talked with, this is definately one of the heavest motors in its class. My boat was modified previous to my purchase by a local dealer to bear the weight. In my case, the lower and upper hulls were actually separating due to the weight on the lower hull. This seperation was occurring right at the rub rail just above the motor. The dealer who fixed it put a 3/4" thick plywood backing plate behind the motor mount inside the hull and re-bolted the motor mount through it. The backing plate was large enough to cover the rub rail joint and bolt to both the lower and upper hulls on either side of the rub rail joint. The dealer also installed two long bolts through the hull and the backing plate which terminated at an aluminum spreader bar on the inside of the port side cockpit on the transom. This arrangement has worked very well on my boat. The dealer said that the lower hull was peeling open and would allow water to enter the hold prior to the fix. I hope this helps. Please check to see if this is the case on your boat as the motor can actually be ripped off at the hull if the rub rail joint fails. I am in the process of trying to sell my 9.9 and get a lighter motor just because I don't want to deal with the weight. Regards

 

[jcherubini]

Outboard bracket ratings.

The average swing-up outboard-motor bracket is typically rated at 20 HP maximum. This does NOT mean that the bracket unit has to have been mounted strongly enough to handle that. However it can be easily beefed-up with extra 'glass across the transom inside (and then reattaching the bracket using new holes). But what is the point? 15 HP is probably more than you will ever need. I would recommend 10 HP at most which would never be too little power during any conditions in which a responsible sailor would be motoring.JC

 

[Lawrence]

15 hp lots of motor

We have a 8 hp motor on the back and find it is lots of power. we had a 9.9 honda but it was heavy and it slowed the boat down