Building a boat around 18hp.

That 18 HP outboard was actively involved with factory racing campaigns and they blatantly lied about the output they had. This is common of most of the 50's through late 60's outboards. A 20 HP on the cowling usually meant you had a detuned 30 HP or a 30 HP that was rated at 75% of it's RPM. They may have used a limiter cap or retarded the timing a bit, but this typically got "adjusted" the first time it was serviced. Don't get me wrong, newer engines easily out preform the older ones, but this is from better design and manufacturing, as well as a better output rating system.

 

It would be apposite to this discussion to know whether it is a short or long shaft motor.

 

Retro version of

 

I Like!

 

What's the length of the amas on that compared to the main hull?

 

eyeballing...20 ft oal... amas 6 to 8 ft

 

18HP 1960 Evinrude,

why not just buy an old 13ft Boston Whaler and go fishing?

FF

 

Sabahcat, any more information on that design?

 

Because I'm looking specifically for a project to build around this particular motor.
Hehe, funny you should mention Whalers though: my current fishing rig IS a 14ft Boston Whaler with a Merc 40 - there's nowhere near enough room to sleep on board and the cockpit is WAY too cluttered. It's fine for day trips, but that's not what I'm looking for.
I also have access to a 25' Zodiac with a Yam225 that I use to run to the beer store and to pull traps.
I'm rebuilding a 15' rowing dinghy that needs a transom and is getting trimmed out in yellow cedar and purple heart, and a 16' freighter canoe that's getting an electric drive.
I'm not looking for just 'a boat'.

Wow, sahbacat, that looks like a hell of a lot of fun. The downriggers might snag on the amas tho...
I was poking through some of the old hydro plans for the same reason but migrated toward a fishing rig. I was painting a bottom last fall and the marina I was in had a 15' mold that they were going to track down the owner of - it looked like a flat, fast hull. They were never able to trace it so I told them to put a price on it but I never heard back. In hindsight I'm ok with that because I think this project will see more use.

I have also looked at Garveys and was looking at a Sea Skiff, but the power requirements seem pretty high for what I'm trying to do. I've also flirted with the idea of a pontoon boat, but that's a little TOO much of a smooth-water boat.

Mr E, it's a short long-shaft
It's 18" with the extension housing.

According to the history I got from the PO...it spent its entire life at a freshwater resort on their 'standby' launch so it was well maintained, rarely used, and saw no salt water. I take all such stories with a grain of salt, but it IS consistent with the condition of the motor. He also had a 7.5 that was a couple years older and had the original manual and sales receipt for it (from the same resort). He bought them and a gorgeous runabout at the estate sale.

Indeed, Paul: while I'm sure I could build damn near anything for someone with deep enough pockets, I don't feel sufficiently comfortable with making fundamental changes to an existing design.

 

I'll second that...

 

Throw that old engine away build whatever boat you want then get the appropriate engine.

 

deadeye,
http://www.boatdesign.net/forums/multihulls/powered-trimaran-27209.html
design by Chris Ostind
if you find more about it please post here, i will too

 

Yobarn,

Have you seen Rick W's tri design?

It's cut from the same cloth...

-Tom

 

Similar to RedWing is my Rocky design. A pure displacement hull that can be pushed a tad faster. The hull is a 5 panel multi chine, with a single centerline panel and it's a taped seam build. The chines are radiused which improves flow around them and eases the hard chine look quite a bit.

The original was intended to be a modest sailboat cruiser, but was built as a powerboat without it's retractable appendages or rig. It has a large cockpit, splash well and a cuddy big enough for two adults to snooze in. You can sleep under the stars in the cockpit too. It's a light boat and material costs are very reasonable. Her principle dimensions are 18' on deck, 16' 9" on the waterline, 6' 9" in beam, draft is about 10" with the motor raised. Because of the hull shape and skeg, she can take to a beach or sand bar bolt upright, which is a handy feature. An 18 HP outboard would be more then enough to handle her with considerable extra punch to bash through waves, currents and contrary winds.

There are lots of these putt-putt types of boats. Maybe a downeast style of hull would be better suited for you. Possibly a box keel design that has some semi displacement potential.

 

I pulled a skier in a 15' Sportabout with a Ward's (Chrysler) Sea King 15 hp outboard in 1974. Two young adult men in the boat and a 16 year old on skis. He took a long time to get up on a plane and by the time he did he was exhausted and couldn't stay up. It was a good test of the OBM limits.