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Author Topic:   13-footer: Engine Weight

krrs posted 10-02-2014 04:01 PM ET (US)
Good day. I am new to Boston Whaler boats and to this forum. Just purchased an late 1960's 13-foot hull. I have a chance to buy a 1999 Honda 25 short shaft, tiller, electric start outboard that weights about 175 lbs. I have been reading where some of the four-cycle engines are too heavy for the classic whalers. Am I ok with this combo? Additional weight will be myself (150-lbs), my wife (120-lbs), fuel and battery.
Cheers,
Ken.
P.S.: Excellent forum
contender posted 10-02-2014 08:45 PM ET (US)
You are fine with the 25
jimh posted 10-02-2014 10:10 PM ET (US)
I don't believe that Boston Whaler ever published a maximum transom weight specification for the 13-foot hull, and certainly not for one made in the 1960's.
There have been some rather informed attempts to impute a maximum transon weigh rating for Boston Whaler boat hulls that have not been given one. See the discussion at:
Maximum Engine Weight
http://continuouswave.com/ubb/Forum4/HTML/002449.html
As you see, the 13-foot hull was not included in that discussion. I really have no idea what might be considered a maximum transom weight on a 13-foot Boston Whaler.
In general, one can say that, as a Boston Whaler boat ages, it is unlikely that its hull and transom become stronger. A c.1960 hull is now over 50-years old. It is prudent to consider that the maximum transom weight ought to be kept in the same range as the original engine weights that might have been used on a 13-foot hull in c.1960.
There is a good discussion about the weight of older outboard engines at
Weight of Older Outboard Engines
http://continuouswave.com/ubb/Forum3/HTML/011042.html
You see in that data that a 25-HP two-cycle outboard from c.1960 was about 120-lbs. Considering the maximum power rating for a 13-footer was 40-HP, such an engine in c.1960 would have weighed about 195-lbs.
On that basis it is probably reasonable to think that a modern 25-HP outboard engine that weighs 175-lbs will be within the general range of transom weight for a classic 13-foot Boston Whaler boat, assuming the hull and transom are in very good condition and retain all of their original strength.
jimh posted 10-02-2014 10:13 PM ET (US)
Are you certain that the Honda 25-HP engine weighs 175-lbs?
krrs posted 10-03-2014 12:29 AM ET (US)
Not 100% sure that weight is correct, I searched the internet and that was what came up. Will check with a Honda dealer tomorrow and see what they say.
leadsled posted 10-03-2014 05:49 AM ET (US)
Don't forget you will have the battery weight near the back.
Jefecinco posted 10-03-2014 07:51 AM ET (US)
A few five gallon buckets could be placed as far to the rear of the hull as possible. Water could be added to the buckets until the transom reaches the design waterline. At around eight pounds per gallon the weight the transom can comfortably carry could be calculated by the amount of water in the buckets.
While far from perfect or scientific the method should provide a reasonable estimate. Deduct the weight of the battery to determine the maximum safe engine weight.
Butch
skred posted 10-05-2014 10:41 AM ET (US)
If you feel you need a newer motor your choice seems fine. The ideal - IMO -for the approximately 330-lb hull would be a 1980's era 25-to 35- hp 2 cylinder, 2-stroke motor at 120 lbs. My 1987 Sport 13 carries a 1981 Johnson 35 hp two-stroke, and performance is quite good at 30 mph+ (depending on load) and excellent fuel economy for a two-stroke. Also, the motor - so far - seems bulletproof.

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Author	Topic: 13-footer: Engine Weight
krrs	posted 10-02-2014 04:01 PM ET (US) Good day. I am new to Boston Whaler boats and to this forum. Just purchased an late 1960's 13-foot hull. I have a chance to buy a 1999 Honda 25 short shaft, tiller, electric start outboard that weights about 175 lbs. I have been reading where some of the four-cycle engines are too heavy for the classic whalers. Am I ok with this combo? Additional weight will be myself (150-lbs), my wife (120-lbs), fuel and battery. Cheers, Ken. P.S.: Excellent forum
contender	posted 10-02-2014 08:45 PM ET (US) You are fine with the 25
jimh	posted 10-02-2014 10:10 PM ET (US) I don't believe that Boston Whaler ever published a maximum transom weight specification for the 13-foot hull, and certainly not for one made in the 1960's. There have been some rather informed attempts to impute a maximum transon weigh rating for Boston Whaler boat hulls that have not been given one. See the discussion at: Maximum Engine Weight http://continuouswave.com/ubb/Forum4/HTML/002449.html As you see, the 13-foot hull was not included in that discussion. I really have no idea what might be considered a maximum transom weight on a 13-foot Boston Whaler. In general, one can say that, as a Boston Whaler boat ages, it is unlikely that its hull and transom become stronger. A c.1960 hull is now over 50-years old. It is prudent to consider that the maximum transom weight ought to be kept in the same range as the original engine weights that might have been used on a 13-foot hull in c.1960. There is a good discussion about the weight of older outboard engines at Weight of Older Outboard Engines http://continuouswave.com/ubb/Forum3/HTML/011042.html You see in that data that a 25-HP two-cycle outboard from c.1960 was about 120-lbs. Considering the maximum power rating for a 13-footer was 40-HP, such an engine in c.1960 would have weighed about 195-lbs. On that basis it is probably reasonable to think that a modern 25-HP outboard engine that weighs 175-lbs will be within the general range of transom weight for a classic 13-foot Boston Whaler boat, assuming the hull and transom are in very good condition and retain all of their original strength.
jimh	posted 10-02-2014 10:13 PM ET (US) Are you certain that the Honda 25-HP engine weighs 175-lbs?
krrs	posted 10-03-2014 12:29 AM ET (US) Not 100% sure that weight is correct, I searched the internet and that was what came up. Will check with a Honda dealer tomorrow and see what they say.
leadsled	posted 10-03-2014 05:49 AM ET (US) Don't forget you will have the battery weight near the back.
Jefecinco	posted 10-03-2014 07:51 AM ET (US) A few five gallon buckets could be placed as far to the rear of the hull as possible. Water could be added to the buckets until the transom reaches the design waterline. At around eight pounds per gallon the weight the transom can comfortably carry could be calculated by the amount of water in the buckets. While far from perfect or scientific the method should provide a reasonable estimate. Deduct the weight of the battery to determine the maximum safe engine weight. Butch
skred	posted 10-05-2014 10:41 AM ET (US) If you feel you need a newer motor your choice seems fine. The ideal - IMO -for the approximately 330-lb hull would be a 1980's era 25-to 35- hp 2 cylinder, 2-stroke motor at 120 lbs. My 1987 Sport 13 carries a 1981 Johnson 35 hp two-stroke, and performance is quite good at 30 mph+ (depending on load) and excellent fuel economy for a two-stroke. Also, the motor - so far - seems bulletproof.