Bought the Engine!

January 16, 2017  Hours spent building to date:  3,261


There is no decision that has taken more research or created more comments from people who have seen this boat than the choice of an engine.

On one of the spectrum was designer Mark Smaalders suggesting that a 60-70 horse four-stroke would accomplish the boat’s mission just fine.  On the other end were those who owned or had  been around a glass fishing boat of about this size: “What are you going to hang on that baby — a 150, maybe twin 100’s?”

My initial thoughts were very much in Mark’s direction.  I have been traveling over the water in sailboats at 6 knots for well over 30 years.  If I could get the Tardis to move 10 knots that would seem like flying.  And although I have built very strong, a big engine pounding the boat into square Long Island Sound waves is just not a good idea.  So a good old Yahama 70 four-stroke, the workhorse outboard of the world, was my initial choice.

But then I started building and adding weight.  The cruising displacement of this boat is 4,750 pounds.  With the fridge, extra tankage, fancy trim, bow thruster, etc.  I estimate I’m at around 5,250.  So I need 10 more horses right there.  But the 4-stroke 75-90 engines really start to get heavy (350-400 pounds), and Mark’s design brief clearly stated that adding weight at the back of the boat was to be avoided.  Then my neighbor Tom Tolla got a couple of gigantic Evinrude E-Tec G2’s for his Grady-White 30 and was extremely happy with them.  And it seems that the wooden-boat design community for this type of boat (Doug Hylan, Sam Devlin, Tolman skiffs) are all going Evinrude two-stroke engines  for several reasons;  a 90 weights 320 pounds, fuel and emissions efficiency is best-in-class, and they are remarkably quiet (I rode in an E-Tec powered boat a couple years ago and would have sworn it was a four-stroke).

The final factor leading to the E-Tec 90 was installation and service.  There are dozens of yards around here doing Yamaha’s and Suzuki’s and Mercury’s, but they all seem small:  10 engines a year?  I’ll tell you about it as it happens, but I really needed somebody to help me with a fairly sophisticated installation and steering setup given that this is a totally custom boat.  Atlantic Outboard is  the biggest E-Tec dealer in New England and they sell hundreds of engines per year.   Paul Cusson the owner really seems to understand what I am trying to do with this boat.   So after hours of measuring I determined that an E-Tec 90 would fit within the space allotted (by about a 1/4-inch, but I have since found that there’s quite a bit of wiggle room).

I did not think of doing this without checking with Mark.  Here’s his take:

I have had a look at the outboard options. The E-TEC 90 (at 320 lbs dry weight) will give you a lbs/hp ratio of 52.6, as compared to 77.6 with the Honda 60 that I used in the weight calculations (239 lbs dry weight). That is quite a difference, and the extra power will result in a significantly higher top speed (I estimate about 20 knots) and enable you to run at lower RPM at cruising speed. 
I also compared engine weights from other manufacturers. The E-TEC has the best power-to-weight ratio, with the 90 hp Tohatsu 2-stroke (MD90) pretty close at 337 lbs. The 4-stroke 90s are mostly around 360 lbs. Another plus with the E-TEC is the high output alternator. 
Just for comparison I checked on larger engines. The 115 E-TEC uses a different block, and takes a leap to 390 lbs. The lightest 115 I found is the Mercury Sea Pro, at 363 lbs. 
I didn’t find detailed engine dimensions online, but you should be able to check that with the dealer, to ensure there aren’t any clearance issues with the engine cover.    
Based on the weight spreadsheet the center of gravity with E-TEC 90 should be fine. No need to relocate anything — best to see how the boat actually trims before deciding to move any weights. 
I am very pleased that Mark thinks the 90 will work out, but my reply to his note was:  “If you ever catch me going 2o knots in the Tardis, stop my grog!”
Obviously, a very attractive package.

Obviously, a very attractive package.







One comment on “Bought the Engine!

  1. Denny Wolfe
    January 16, 2017 at 8:10 am #

    You will love the etec for its lack of maintenance and low fuel burn too.

    Last season my 60 HP used 56 oz oil and 46 gal gas. I used to dump 5 qts of oil every season. Use the expensive oil, zero smoke.

    Also, they have a lean burn mode when running below about 1500 rpm. I get 25 mpg at 4 mph (perfect putting around eating and drinking speed) with my 22′ runabout.

    I follow your blog faithfully and have enjoyed watching the progress. Beautiful craftsmanship, good writing too.

    MCDENNY from the WBF.


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