20' center console and 90hp evinrude. What will cruising speed be?

[Bushwacker]

When folks start asking about how a SeaCraft will perform with a relatively small lightweight outboard, they need to recognize that back in the early-mid 60’s when Carl Moesly designed the 21 and 19/20' boats and came up with the unique Variable Deadrise Hull (VDH), THAT’S ALL THAT WAS AVAILABLE! They were DESIGNED for small lightweight motors! The biggest outboards available back then were the I-6 Merc and the V-4 OMC, both of which weighed less than 300 lbs and put out no more than about 100-120 HP! The most exceptional result of the design was that not only did it ride as well or better in rough seas than other more extreme deep-V’s with higher deadrise, it also could plane at much lower speeds with heavier loads than competitive designs with the same power! The average boater that’s not familiar with this history probably has no idea how efficient the SeaCraft hull is compared to most of the competition! And it's unfortunate how many folks ruin this characteristic, screwing up the boat's CG by installing such big motors that are MUCH heavier that what they were originally designed for!

You can learn a lot more about how efficient the SeaCraft VDH is if you read “The Amazing Mr. Moesly” article by Steve D. Antonio in “Professional BoatBuilder” magazine (you can find it in the Literature section on CSC or on Carla’s website @ http://www.moeslyseacraft.com/upload...oeslyp1-16.jpg.) About halfway through the article, there’s a great story about a competition conducted in the early 60’s on Biscayne Bay between the Moesly 21 and a couple of other boats with successful racing histories (I’m guessing maybe Bertram and Magnum or Formula) by a “secretive government agency”. The government had specified the use of a particular V-8 I/O power plant, and required that they be able to carry 9 people and several hundred pounds of sandbags to simulate a certain amount of gear and cruise at a certain speed. The Moesly 21 met all performance requirements but neither of the other boats could even get on plane with the required load! The story relates how Moesly offered to “help” his competition by taking one passenger and several sandbags off of each of the other boats, but they still couldn’t get on plane! He then took the government agents and the extra passengers for a ride around the bay on his now “overloaded” 21, showing that he had no problems getting on plane or holding a good cruise speed with the extra load! Needless to say, he won the contract on the spot for a significant number of 21’ and later 27’ boats that were supposedly used for “covert activities” roughly around the time period of the Bay of Pigs incident! A friend of mine that owned a Moesly 21 and whose dad originally owned my Seafari, told me that he once saw one of those government 21’s at Brown & Hauptner Marine where I bought my boat, with a bunch of steel reinforcement up under the front deck. Turns out it was a mount for a .50 cal machine gun!

Some later SeaCraft brochures claimed that the VDH design, with the same weight and horsepower, was about 10% faster than comparable deep-V’s of the day. I suspect this claim is based partially on the above story, along with the results of much testing that Moesly did at Lake X in preparation for the many races he entered. I’ve noticed one subtle detail in the 19 & 20’ hulls, that may also be present in the 21, 25 Seafari, and 27’ hulls, that might explain this exceptional performance . . . if you sight back aft along the chine towards the transom, you’ll notice that the last 10' of the outer panel angles down, to create a slight wedge shape. This would act like a trim tab to provide extra lift to help get on plane at low speed, but the outer panel is almost completely out of the water at speeds over about 40 mph, so this feature would cause no additional drag or have any impact on top speed! This is but one example of the many subtle but brilliant ideas that went into Moesly’s designs! Denny

[Fr. Frank]

Originally Posted by Bushwacker

there’s a great story about a competition conducted in the early 60’s on Biscayne Bay between the Moesly 21 and a couple of other boats with successful racing histories (I’m guessing maybe Bertram and Magnum or Formula) by a “secretive government agency”.

Carl did reveal the name of the agency a few years back, but I think it was inadvertent, so I won't repeat it here. He also named both Formula and Donzi as among the 5 or 6 early competitors for that contract back in '64.

He said Donzi made a prototype 22' patterned after their race 28' that "just wouldn't go", and Formula, (which had just been bought out by AMF) submitted the early 233, which needed a lot more power to get on plane.

That contract as awarded to Seacraft eventually was modified to included both 23' & 27' hulls along with the original 21'.

The 23' and 27' hulls later built for the unnamed agency were both called "SeaVette". Only the 23' SeaVette was later introduced to the public.

Carl was not specific, but did say there were 3 prototype 27' SeaVette boats built in '67, each different, and of the later government 'production' 27' SeaVette he said, "of course, we never built very many of them, just a very few..."

More rare than the 15' Scampi...


As for the thread, I rigged lots of early 20' Seacraft hulls with 85-115hp V4 motors, and even with a single 70 hp. Johnson once. It, too, ran and planed just fine.

[Bushwacker]

Fr. Frank,

Thanks for providing additional details/date on the participants in the government's "Biscayne Bay Shootout"! Steve D's article indicated there were only 2 other participants, but there were so many competitors on Miami's "Thunderboat Row" back in those days, I figured there were probably more than two! Do you know what I/O setup they used? I heard they used a big block Ford? Denny

[Fr. Frank]

All Carl said was that they were BB Fords with the TRS drive behind a BW tranny.

The larger TRS drive was still pretty new, having been just introduced in '62. It was called the "Mercruiser II" when it was introduced.

I imagine that in 1964 the motors probably were actually medium block motors. i.e., the FE series engines, (332/352/360/361/390/406/410/427/428) which many called "big blocks", made from 1958–1976. The later 370/429/Boss 429/460/514 motors are also medium block motors, being developments from the FE series.

Fords true big blocks in that day were the MEL series (383/410/430/462) block, and the "SuperDuty" series (401/477/534) big blocks. Ford actually made a 601 c.i. version of the MEL block for one year only, in 1963, for use as a passenger bus motor.