Appropriate motor size. This is a really a boat topic and not engine topic :-).

[I'D RATHER B FISHN]

View attachment 128415Hello everyone,

I'm wondering what size motor should I put on this rig. It's under restoration, but I'm always looking on craigslist for a motor that will eventually go with it. It doesn't have a max h.p. rating decal on it and the boat manufacturing company is out of business. Anyone out there have a rig that looks similar and could give me some ideas. I'd like to put a 40-50 2 stroke on it. Does this seem to much?

thanks,
IRBF

 

[Bondo]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

Ayuh,.... The Size of the hull would be a nice bit of info....

 

[pootnic]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

Nice boat....
Alittle more information would help though,length,width,stern hight....Pretty big V up front and if it was registered(I see #'s) maybe you can find out more information there.
From the picture a 40/50 doesn't look to crazy...

 

[Home Cookin']

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

yes. stay under 40. 25 will be fine (if it's a copy of a 13' whaler, as it appears)

 

[JB]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

Looks like it could handle 40HP, but I agree with Home Cookin' that a 25 would do fine. That is what I ended up with on my Whaler Sport 13.

 

[I'D RATHER B FISHN]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

Sorry, I'm sure the size would help. 15'3".

 

[kfa4303]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

I would stay under 40 hp too. I think you'll be surprised how fast a 25-35 will push her. I had an old '66 33 hp Big Twin that was a screamer, almost too much motor for the 14' skiff I had it on. Of course, I'm no daredevil, but I think anything over 40 would be not only heavy, but a little scary. Great little boat though.

 

[CheapboatKev]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

Anything in the 40hp range would just be unsafe I am sure
15 to 25 would be perfect. Depending on what you want to do with it/use it for even a 9.9 would do and let you on restricted HP lakes

 

[smokeonthewater]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

soo we have 16' boats all over the place with 140 hp but he can't run 40 on a 15'er??

what brand of boat is this?

 

[Thalasso]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

soo we have 16' boats all over the place with 140 hp but he can't run 40 on a 15'er??
what brand of boat is this?

I think it is going to depend on hull design, length , beam, and displacement. ( Edit ) Just saw the boat. 40 might be a little much for that boat.It doesn't look to be very heavy. The weight of the 40 might just be to much.

 

[I'D RATHER B FISHN]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

Thanks for the replies, especially thoughs concerned with safety first. I don't know the make of the boat except to say that the first 3 characters of the HIN# are CFM, Custom Fiberglass Manufactures. They have long been out of business. I will be using her in the Biloxi bay (in Mississippi) which is off the Gulf of Mexico. Not offshore or anything crazy like that.

Thanks again,
IRBF

 

[26aftcab454]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

look all over the internet looking for a simaler boat and see what they run.

 

[Ike-110722]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

There are simple formulas for calculating outboard horsepower for boats under 20 feet. Look here and find the correct formula for your boat depending on the setup. These are the formulas the USCG and the boating industry uses. Don't guess.

http://newboatbuilders.com/pages/hp.html

 

[smokeonthewater]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

while they are indeed out of business I was able to find contact info.... might be worth a shot
http://boat-manufacturers.findthebest.com/l/1520/Custom-Fibergls-MFG-Inc

 

[M9.9]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

There's a registration number on it, maybe you might check-out engine specs for that boat, that way?

 

[I'D RATHER B FISHN]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

smokeonthewater,
Thanks for the link. I made the call this morning to Mr.Franklin and he is fact the original owner of CFM. He was able to offer up from memory recollection that there were two models similar to the one I've described to him. He gave me the estimated dimensions of both and the HP rating for both. The first model was around 15' and 72" at it's widest point and rated for a 70hp. The second model was a 14', he couldn't recollect the width, but said that one was rated for a 40-50hp.

Based on my description of the boat he thinks mine is the first model. Even though he offered up the rating of 70hp, I'm a little hesitant to put something with that much power on her. I know I don't ever have to open the throttle to max power, but it's the sheer weight of such an engine that concerns me on that size of a boat.

Peter,
I used your link to pull the horsepower calculation and came up with 60hp. I think I'm going to go with a 50hp. I'm really not looking to build her back up for speed. This boat will be my second boat next to my offshore boat and will serve a completely different purpose of kicking around the bay with my 3 year old son. And hopefully if I take good care of her, it will be the first boat he will learn how to drive in the coming years.

I have one other question. I don't want to duplicate new threads, but I would like to start one that shows my project from beginning to end. This way I can consildation all questions into one thread and just let it constantly grow as the project progresses. Any objections or suggestions on me doing this?

Again,
Thanks for the advice.
IRBF

 

[ezmobee]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

I have one other question. I don't want to duplicate new threads, but I would like to start one that shows my project from beginning to end. This way I can consildation all questions into one thread and just let it constantly grow as the project progresses. Any objections or suggestions on me doing this?

None at all. Go ahead and start a new thread in the Resto section for your project.

 

[Maclin]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

The HP ratings for hulls, as I recall from an info search back in the last century before internet, is as much about the build/trength of the boat's transom and hull stiffening structure as it is the length or intended use.

For example a 15.5 foot bowrider trihull would be rated max 70hp while a similar "open" fishing boat like the one in your pic was more like 55hp max. The fishing boat with a 55 probably ran the same as the trihull with a 70, as it would be lighter than the trihull style boat.

From that same era, here is Mr. Mom's advice....."40, 41, whatever it takes..."

 

[H20Rat]

Re: Appropriate motor size. This is a really a boat topic and not engine topic .

There are simple formulas for calculating outboard horsepower for boats under 20 feet. Look here and find the correct formula for your boat depending on the setup. These are the formulas the USCG and the boating industry uses. Don't guess.

http://newboatbuilders.com/pages/hp.html

That test is 100% worthless for this case. Read to the bottom... There are special exclusions for various categories, one is 'outboard powered'. In that case, it is the test course method, which I'm assuming is an actual water test to see how it performs and safety of the hull.

As far as the recommendations in general, I've run them before, and my boat comes up with 125 or so max hp. My boat, USCG certified of course, comes with various powerplants from the factory. The SMALLEST is 175hp, the largest being 240hp. So obviously the water test means far more than the spreadsheet.

If it were me, I'd put a 40 on there without a second thought. Depending on how it sits in the water, you might need to push a little weight (battery/gas tank) forward some though. Of course, I'm also the guy that doesn't have a problem adding a little extra horsepower to a car, I know that scares lots of people... Just because you have a whopping 40 hp behind you doesn't mean you have to drive around with it floored all the time.

(something to ponder, there is only about 30 pounds difference between a 4 stroke 25hp and a 2 stroke 40)