Overpowering by 2 HP?

[Luke000]

Hello, This is my very first post in this forum and I soon will have many more. I recently just acquired an old aluminum boat (1956 duratech S13) and staring in the very early stages of a full restoration/ modernization (The boat is purchased but at a cottage waiting for new tires for the trailer to bring it all the way home) Anyways, we will be putting in a brand new outboard that we will purchase. There is no mention of HP capacity anywhere on the boat but an old catalog says the max recommended is 18HP; The choices of outboards we have narrowed down to are a 15HP Evinrude, 15HP Mercury, and a 20HP mercury. All with short shaft, remote steering/ throttle, electric start, manual trim, 4 stroke. They are all in the same ballpark-ish price and within 2lbs weight difference (both Mercury are lighter than Evinrude FWIW). Would you think we would run into catastrophic failure if we bought the 20HP mercury and overpowered the boat by 2HP? Would the boat lag with a few people cruising in it with the 15HP?

A side note: the transom will be replaced, we have had many boats in the past, and this will be used for just cruising on inland lakes, not a fishing boat or a ski boat.

Any input is appreciated, and please excuse if this is a common question, I did search and came up with nothing.

 

[matt167]

Re: Overpowering by 2 HP?

Weight is the key here and part of the old ratings. You say brand new, which means 4 stroke for those HP's. The old 2 strokes will be much lighter.. Also, the rating was for a crankshaft rated HP. not prop rated as today, so your 2hp overpowering is actually a lot more.. I would get a newer 2 stroke 15hp. Mid 1990's Johnson/ Evinrude will do very well, but a Merc, Yamaha, Tohatsu 2 stroke, whatever you can get really, could do just as well.

If your stuck on 4 stroke, cut the middle man and get a Tohatsu. Evinrude and Mercury's smaller 4 strokes are all Tohatsu engines so it's just what color you want and what you want to spend. If you can live with grey, Tohatsu will be the cheapest

 

[Home Cookin']

Re: Overpowering by 2 HP?

going from 18 to 20 is no problem. The weight differential between a 1963 two stroke and 2013 4 stroke may be the issue.

 

[Luke000]

Re: Overpowering by 2 HP?

Weight is the key here and part of the old ratings. You say brand new, which means 4 stroke for those HP's. The old 2 strokes will be much lighter.. Also, the rating was for a crankshaft rated HP. not prop rated as today, so your 2hp overpowering is actually a lot more.. I would get a newer 2 stroke 15hp. Mid 1990's Johnson/ Evinrude will do very well, but a Merc, Yamaha, Tohatsu 2 stroke, whatever you can get really, could do just as well.

If your stuck on 4 stroke, cut the middle man and get a Tohatsu. Evinrude and Mercury's smaller 4 strokes are all Tohatsu engines so it's just what color you want and what you want to spend. If you can live with grey, Tohatsu will be the cheapest

I agree about the weight of the 2 stroke, If it was up to me I would be getting a 50's 18HP and restoring/ rebuilding that as well but the engine decision is that of my dads (the one I am doing the restoration with) and he is set on a brand new 2013/14 motor and we are stuck with a 4 stroke.

I will be on the lookout for a tohatsu DEALER to give me a quote because according to the tohatsu web site it is 5-700 dollars more than what we can get at a local place: Evinrude or Merc

 

[matt167]

Re: Overpowering by 2 HP?

check here. Discount Tohatsu Outboards and Nissan Outboard Motors

 

[Luke000]

Re: Overpowering by 2 HP?

check here. Discount Tohatsu Outboards and Nissan Outboard Motors

Yeah that is $500 more than the merc at West Marine (part# 10322568) and "Remote Steering/Control models may NOT be shipped due to manufacturer restrictions and must be installed on your boat at our Cookeville, TN location. Prices below are for remote models and include taxes and installation. Contact us to purchase and schedule an appointment for installation."

 

[matt167]

Re: Overpowering by 2 HP?

Isn't a Duratech S13 an open tiller steer utility? In any case, if you can get a Merc cheaper than a Tohat, go for it. Same thing in black paint. Great motors in any case..

The reason Online Outboards won't ship remote steer engines is due to the warranty. Tiller motors are considered portable ( removable ) but remote control are considered permanent install, so the warranty only covers professional installs with remote controls. Online outboards and others bypass that with remote install kits but the cost probably adds up to a local dealers price

 

[Luke000]

Re: Overpowering by 2 HP?

Isn't a Duratech S13 an open tiller steer utility? In any case, if you can get a Merc cheaper than a Tohat, go for it. Same thing in black paint. Great motors in any case..

The reason Online Outboards won't ship remote steer engines is due to the warranty. Tiller motors are considered portable ( removable ) but remote control are considered permanent install, so the warranty only covers professional installs with remote controls. Online outboards and others bypass that with remote install kits but the cost probably adds up to a local dealers price

Nope! The boat is a closed bow runabout , has steering and an old Johnson control Box set up in it now. That is what I figured about the installation on the remote vs tiller.

Do you think the 20HP would be overkill or the 15 is under powered for the boat (biggest fear)?

PS: Picture of the boat on the side of the road where we found here.

 

[matt167]

Re: Overpowering by 2 HP?

Both are inline 2's at 21.4 CID, so your weight difference will be about zero, and considering the prop hp rating compared to the old crank hp rating, either will be an upgrade to anything that boat could have had years ago. 15hp will likely be adaquate and be at that 18-20hp crank hp rating, but the 20hp model will probably put 22-25hp at the crank.. I would go with a 20hp. It's a nice boat and will be worthy of the modern power you give it.

 

[82rude]

Re: Overpowering by 2 HP?

duratechboats.com - Duratech History that boat screams 1956 evinrude 15hp! or as a consolation motor how about a Yamaha f15/20 ?

 

[Home Cookin']

Re: Overpowering by 2 HP?

since you don't mind having a motor newer than the boat, but still want "classic" see if you can find an 18 from 1962-1970. great, bullet-proof motors.

 

[Luke000]

Re: Overpowering by 2 HP?

since you don't mind having a motor newer than the boat, but still want "classic" see if you can find an 18 from 1962-1970. great, bullet-proof motors.

I like that option, however my dad is going to be cutting the check for the engine and he is dead set on a brand new motor with a warranty (yes he is one of those people :laugh: ) So unfortunately thanks for our government it looks like we are stuck with a 4 stroke. I think I will work on looking at the 20HP if nobody thinks this is a bad idea/ boat will not handle it.

 

[Willyclay]

Re: Overpowering by 2 HP?

I think I will work on looking at the 20HP if nobody thinks this is a bad idea/ boat will not handle it.

The picture below is of an Orlando Clipper boat that has been restored/rebuilt to handle a Yammy 90 motor. Although I do not know its exact length, I believe it is less than 15 feet based on the comments by the iboats member who posted the picture. I am not suggesting you put a 90HP motor on your boat, but just want you to focus on the quality of your transom rebuild before you clamp anything on that 50 year old boat. Good luck!

http://forums.iboats.com/attachment.php?attachmentid=162911&d=1344376482