Will 40 hp do it?

[acabtp]

Hey there. I'm new to powerboating and have been doing some research here on iboats to find out what it will take to get my vessel up on a plane. The boat is a Cobia Sunskiff 156 which I have not been able to find too much info about online. It's a 15' boat with a 6'10" beam and the hull weighs about 700 lbs. Maximum weight of persons, motor and gear is 1165, so total max weight would be around 1865 lbs.

It was rated for up to a 90 hp motor and had the remnants of a 90 hp Mercury on there when I got it, but I really am just looking for something that will move the boat around on a plane. I just want to go fishing, not win races or pull waterskiers. I have found a good deal on a 40 hp Johnson and was wondering if that would do the trick. If 40 hp won't do it, what do you guys think will? I have looked at charts, but don't have much experience with this.

Here are some pictures of the hull.

Thanks!
Tom

 

[robert graham]

Re: Will 40 hp do it?

A 40HP will move it O.K., a 70HP would be better, a 90HP probably more than you need. I run a 90HP on an 18' boat and rarely use the power except to get up on plane quickly. Good Luck!

 

[acabtp]

Re: Will 40 hp do it?

A 40HP will move it O.K., a 70HP would be better, a 90HP probably more than you need. I run a 90HP on an 18' boat and rarely use the power except to get up on plane quickly. Good Luck!

Cool, thanks for the info. I will probably start with the 40 hp this season, and upgrade later if needed. Any other opinions?

 

[robert graham]

Re: Will 40 hp do it?

My son just sold his boat very similar to yours with a Yamaha 40HP on it and it was fine for just cruising around and fishing, maybe all you need. Good Luck!

 

[Andy in NY]

Re: Will 40 hp do it?

skiffs generally are pretty light... a 40 will get you around and on plane, probably around 25 mph or so...

 

[bonz_d]

Re: Will 40 hp do it?

From the pictures, that looks like the remains of a Evinrude V block engine. Did the boat have a steering console in it?

My impression from the pictures is that a 50-60hp would be better suited than a 40hp.

 

[coolguy147]

Re: Will 40 hp do it?

i prefer to have extra power for reserve. you don't have to run WOT all the time

 

[acabtp]

Re: Will 40 hp do it?

From the pictures, that looks like the remains of a Evinrude V block engine. Did the boat have a steering console in it?

I looked at it again and you are right... OMC label, model # starting with "E90". The boat did have a steering console, but was gone when I got it. I actually found the guy who bought the console out of it here on iboats, small world. I have to build a simple console to mount the controls to for testing until I get the original one (fingers crossed) or something else.

My impression from the pictures is that a 50-60hp would be better suited than a 40hp.

i prefer to have extra power for reserve. you don't have to run WOT all the time

I find it hard to disagree with "MORE POWER!"... but I found a 1970 40 hp Johnson (big twin) that hadn't been run in a few years on Craigslist for cheap. It looks to be in good shape, so I have my fingers crossed to get it started this weekend after I rebuild the carb. I built the outboard motor stand last night, but made it 30" wide instead of 24" so that I could use a regular galvanized garbage can for the test tank.

I figure that if the 40 turns out to not be enough power, I'll just sell it and make a couple hundred bucks which I can then put towards a bigger motor this fall.

 

[bonz_d]

Re: Will 40 hp do it?

Sounds like a great plan and I would probably do the same thing.

Is there a capacity plate on the transom anywere? That would be a better indication of what engine would be most suitable.

I have a 14' Lund LTD with side console which I picked up w/o an engine, it's rated for a 35hp and my 1st engine on it was an 18hp tiller which worked ok and ran it until I found a nice 35hp.

Looks like a very nice fishing platform. Should be stable and comfortable.

 

[acabtp]

Re: Will 40 hp do it?

Is there a capacity plate on the transom anywere? That would be a better indication of what engine would be most suitable.

No, apparently the placard with the weight and HP capacity was on the console. I found out from the guy who bought the console (before I bought the boat) that it's rated for 5 persons @ 675 lbs, 1165 lbs persons/motor/gear, and 90 hp.

Looks like a very nice fishing platform. Should be stable and comfortable.

Thanks, I am looking forward to it!

 

[Challenger84]

Re: Will 40 hp do it?

I have a great running 70hp Johnson on a 16' er and it really gets up and go!

 

[kenmyfam]

Re: Will 40 hp do it?

60 HP + up to and including 90 HP would be the ideal HP range for that boat. A 70 HP Johnnyrude would be ideal.
My 2 cents.

 

[tashasdaddy]

Re: Will 40 hp do it?

you need minimum of 70% of the boats rated HP. which would be a 63 hp, not made so 70 hp and up to the 90hp.

 

[bonz_d]

Re: Will 40 hp do it?

acabtp, sorry I didn't read your linked post before I posted otherwise I'd have known about the capacity plate.

Pretty wild story though that you found the owner of the original console and it's still intact. What do you think the odds are? same as the lottery?

As per the others a larger engine would be ideal but you can still go with your plan and use the 40 until you find a replacement. May have to really prop it down to obtain the correct rpm range, bigger diameter and less pitch.

 

[JARED T]

Re: Will 40 hp do it?

my1984 , 40 hp johnson gets me around just fine and i have a 15 1/2 ft kingfisher and she moves pretty good on the lake.i dont need anything bigger.

 

[will941s]

Re: Will 40 hp do it?

Build the console, rig the wires, clean her up....and in the meantime, keep scanning Craigslist. Good 60's, 70's and 90's go on the there all the time for really cheap. Seen some Evinrude 70's go for as little as $400. My buddy just bought a 1981 Johnson 75 for $350 and it was water ready. If you don't have to settle, keep looking. Not worth the trouble of setting it up, bolting it down....not liking the motor; then having to take it off and re-rig something else. Do it right the first time. If it was rated for a 90 then theres something about the boat that engineers decided it needed the power on the back,