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Author Topic:   Re-power 13-foot
thebulkinator posted 05-05-2004 07:47 PM ET (US)   Profile for thebulkinator   Send Email to thebulkinator  
My father [is considering re-powering] our 13-foot Boston Whaler boat with a 40-HP four-stroke that weighs 220-lbs. Would this be too much weight for this hull? I'm thinking a 40-HP two-stroke or a 30-HP four-stroke. Also will a 40-HP motor make this Boston Whaler boat fly? Thank you all, Ben
David Jenkins posted 05-05-2004 08:26 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
Weight not a problem if you move fuel and battery forward and don't use a jackplate. The 50 hp Honda at 203 pounds would be an even better choice.
thebulkinator posted 05-05-2004 08:41 PM ET (US)     Profile for thebulkinator  Send Email to thebulkinator     
The only problem is I would have to use a jackplate as it is a 20" shaft and its a 15" transom.
David Jenkins posted 05-05-2004 09:15 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
You might want to use the CMC vertical extensions with shims. They are relatively light-weight and only set the engine back a half inch.
2manyboats posted 05-06-2004 08:34 AM ET (US)     Profile for 2manyboats  Send Email to 2manyboats     
4 years ago we repowered our 1973 13-foot with a 25-HP four-stroke Yamaha that weighs 190 lbs. (about the same as a 40 two-stroke). I felt that was about as heavy as I would go. We left the battery in the stern but did move the gas tank to forward of the front seat. With a full tank of gas, two adults, and ice chest we run about 24 kts. in flat water and cruise all day at 18 kts.

If 220-lbs. is OK, a 70-HP two-stroke only weighs 228-lbs . I just might no better not.

Whalerologist posted 05-06-2004 04:39 PM ET (US)     Profile for Whalerologist  Send Email to Whalerologist     
I know that I posted this before, but having gone through the engine replacement scenario last year, I found the best horsepower for the boat to be either a 40- or 50-HP two-stroke. Just my opinion on the two-stroke.

When my 1987 OMC 40 twin took a dive, I opted for a two-stroke 2000 Johnson 50-HP, which weighed about 190 lbs. It has the power trim and tilt. I bought the engine through [perhaps --jimh] from a Florida dealer who was literally giving them away (well almost anyway).

Having just removed the 40 HP Johnson, there were no new holes to drill. All I did was shim the new engine to get more postive trim (out) since I am not so concerned with holeshot as I am top end. I can now over-trim the engine to the point (I don't know if this is correct term) where she "blows out."

Anyway, swinging a 19-inch-pitch prop, she runs 47 on GPS and will cruise at 40 all day long (giving me a pounding); maximum RPM is 5500 on my OMC tach (electronic model). Holeshot is a bit slow with the 19, but the top end surprises a lot of bigger boats out there.

Personally, I'd go with the lighter two stroker (maybe an E-TEC™), but they are pricey still.


OutrageMan posted 05-06-2004 08:36 PM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     
I have a 50 -HP Yamaha 4 stroke on my 13 Dauntless. A bit slow to plane, but it sure sips the fuel.


jimh posted 05-07-2004 07:44 AM ET (US)     Profile for jimh  Send Email to jimh     
Inasmuch as the boat has a 15-inch notched transom, I would be particularly concerned with the engine weight and how it might affect the trim of the boat.
Mumbo Jumbo posted 05-09-2004 08:56 AM ET (US)     Profile for Mumbo Jumbo  Send Email to Mumbo Jumbo     
Too much weight. You might want to consider the 25 Yamaha four stroke with power trim and tilt. This engine weighs 156 pounds and is more than adequate for two adults and all the gear they could reasonably carry. Your problem is the notched transom. I would strongly consider having the transom altered by a glass repair shop to raise it to 20".

Andrew posted 05-15-2004 01:44 PM ET (US)     Profile for Andrew  Send Email to Andrew     
my answer regards old mercs only, the engines I tried and still love so fondly.

The old 20 (merc 200) is the minimum (just ok for lightweight applications), the newer shnuerle larger capacity 20 is better, the old 2 cyl 40 is fun and was the engine to buy. Today all have forgotten the 40 HP limit and I would like to try the old 4 cyl. 50 (one of the very best mercs!!) maybe without electric start and trim for weight reasons.
To be honest I would really like to make one for myself!
Let us know, but do not discard old engines, you often spend less and get more!


p.s. blue interior is a must with these engines!

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