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Author Topic:   1963 13-footer Curved Transom

douglasemitchell posted 11-20-2014 12:36 PM ET (US)
I am re-powering a 1963 classic 13-footer with a 1995 Evinrude short-shaft two-cycle 40-HP. Since the transom is curved, the new motor mount does not [fit] flush. I added two aluminum plates about 3/16-inch thick to fix this, but it is still not right. How [is one] to mount [an engine]?
Also, on the inside of the well the holes I drilled go into a part of the transom that is 2-inches wider and seems to been devoid of wood [in] the last 2-inches. Will these bolts still work in this area? Thanks in advance for help.
Powergroove803 posted 11-20-2014 01:13 PM ET (US)
I had a 1963 13-footer. I added the minijacker plate, but I also had a 25-inch shaft. I suppose you do have the cutout in the transom as well, so [unclear] may work anyway. My engine was still too long even with the jackplate. I paid about $80 for the plate brand new.
jimh posted 11-20-2014 03:30 PM ET (US)
The only method I know of for accommodating the irregular mating that occurs between a curved transom and a flat engine mounting plate is with shims. The shims could be made from hardwood and shaped to exactly fit the curve of the transom. The shims have to be tall enough to fill in the gap between the engine mounting plate and the transom.
The location of wood reinforcement embedded in the transom of a c.1963 Boston Whaler 13-footer is shown in the wood locating diagram drawn by Boston Whaler and reproduced in digital form here. See
http://continuouswave.com/whaler/reference/13/
for a hyperlink to the diagram, or follow this link:
http://continuouswave.com/whaler/reference/13/graphics/BW13-wood.pdf
According to that drawing from Boston Whaler, there should be embedded wood reinforcement across a width of 22-inches. If you are drilling holes that do not land into the wood reinforcement, those holes would have to span more than 22-inches. That is a preposterously wide spacing for engine mounting holes.
The standard dimension for the BIA engine mounting hole arrangement has the top set of holes spaced apart by a width of only 12-7/8-inch on-center. This is no reasonable way to believe that an engine with a BIA mounting bracket installed on the keel centerline would have holes for mounting that were beyond the area of embedded wood reinforcement in the transom of a 13-foot Boston Whaler boat. There are only two reasonable conclusions:
--the transom has been modified from original by some unscrupulous modifier of transoms, and the embedded wood has been removed
--the engine mounting bracket is some sort of bastard design and does not conform to the BIA standard.
The BIA standard is, by the way, based on OMC's design. It seems quite reasonable to assume that a 1995 Evinrude 40-HP has the BIA mounting bracket and holes as described. For more on the BIA hole layout, see the FAQ:
Q9: What is the Standard Transom Hole Layout?
http://continuouswave.com/whaler/reference/FAQ/#Q9
On the corollary topic of shaft length, the transom on a c.1963 Boston Whaler 13-footer is notched, and the recommended outboard engine shaft length is 15-inches. (See the Reference article on the 13-foot hull for more details.) It is quite good fortune you found a 1995 Evinrude with a short shaft (15-inch shaft), as those engines are hard to acquire these days. By using a short shaft engine on the notched transom, you will be unlikely to need to use any sort of engine adaptor or set back bracket to accommodate the shaft length. Such devices are only used when the engine shaft length is too long for the transom height. That is not the case here.
jimh posted 11-20-2014 04:12 PM ET (US)
Engine mounting bolts that are not in holes with wood reinforcement are not going to work.
jimh posted 11-21-2014 06:52 AM ET (US)
The topic of a curved transom on an older 13-footer and mounting a newer engine with a flat mounting plate is mentioned in
http://continuouswave.com/whaler/cetacea/cetaceaPage56.html
If you look closely at the illustration (hyperlink below)
http://continuouswave.com/whaler/cetacea/cetaceaPage56.html#56-03
you can see the shims that were fabricated to permit a better fitting of the flat surface of a mounting bracket to the curved transom. In this particular instance the mounting used a intermediate bracket to correct for the shaft length problem, but the same sort of approach using shims would work for the bracket of an engine that was mounted directly to the curved transom.
douglasemitchell posted 11-21-2014 12:10 PM ET (US)
Thanks for the Insight..with this info I have plans to make two shims out of 1/2 thick aluminum and bolt engine directly through engine, shim and transom for the two top bolts. The lower bolts have already been drilled(urgh) so most likely use lags as described in this article and possible add two additional bolts trough my aluminum shims for extra strength through the transom near upper engine bolts.
clearly i don't see the need for a jack plate since my engine is the correct 15" shaft.. And mounting the jack plate as described still requires the same sort of shims.
Jim how do you post pics on this site? Again thanks to all. Dug
dfmcintyre posted 11-21-2014 01:03 PM ET (US)
Doug -
(This suggestion may be too late)...
Do you have a good fiberglass shop in your area? If so, run the idea of fabricating shims out of glass and epoxy and then painted (or gelcoated) right onto the transom. Could make it look factory.
Regards - Don
douglasemitchell posted 11-22-2014 09:22 AM ET (US)
Great ideal. My boat currently has the original gelcoat from 1963 in good shape.. In a year or two I have plans to redo gelcoat. At that time I will look into fiberglass shims and gelcoat. For now just enjoying using the boat. I want reliable power and mechanical all working.
Thanks for the ideal.
dug

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Author	Topic: 1963 13-footer Curved Transom
douglasemitchell	posted 11-20-2014 12:36 PM ET (US) I am re-powering a 1963 classic 13-footer with a 1995 Evinrude short-shaft two-cycle 40-HP. Since the transom is curved, the new motor mount does not [fit] flush. I added two aluminum plates about 3/16-inch thick to fix this, but it is still not right. How [is one] to mount [an engine]? Also, on the inside of the well the holes I drilled go into a part of the transom that is 2-inches wider and seems to been devoid of wood [in] the last 2-inches. Will these bolts still work in this area? Thanks in advance for help.
Powergroove803	posted 11-20-2014 01:13 PM ET (US) I had a 1963 13-footer. I added the minijacker plate, but I also had a 25-inch shaft. I suppose you do have the cutout in the transom as well, so [unclear] may work anyway. My engine was still too long even with the jackplate. I paid about $80 for the plate brand new.
jimh	posted 11-20-2014 03:30 PM ET (US) The only method I know of for accommodating the irregular mating that occurs between a curved transom and a flat engine mounting plate is with shims. The shims could be made from hardwood and shaped to exactly fit the curve of the transom. The shims have to be tall enough to fill in the gap between the engine mounting plate and the transom. The location of wood reinforcement embedded in the transom of a c.1963 Boston Whaler 13-footer is shown in the wood locating diagram drawn by Boston Whaler and reproduced in digital form here. See http://continuouswave.com/whaler/reference/13/ for a hyperlink to the diagram, or follow this link: http://continuouswave.com/whaler/reference/13/graphics/BW13-wood.pdf According to that drawing from Boston Whaler, there should be embedded wood reinforcement across a width of 22-inches. If you are drilling holes that do not land into the wood reinforcement, those holes would have to span more than 22-inches. That is a preposterously wide spacing for engine mounting holes. The standard dimension for the BIA engine mounting hole arrangement has the top set of holes spaced apart by a width of only 12-7/8-inch on-center. This is no reasonable way to believe that an engine with a BIA mounting bracket installed on the keel centerline would have holes for mounting that were beyond the area of embedded wood reinforcement in the transom of a 13-foot Boston Whaler boat. There are only two reasonable conclusions: --the transom has been modified from original by some unscrupulous modifier of transoms, and the embedded wood has been removed --the engine mounting bracket is some sort of bastard design and does not conform to the BIA standard. The BIA standard is, by the way, based on OMC's design. It seems quite reasonable to assume that a 1995 Evinrude 40-HP has the BIA mounting bracket and holes as described. For more on the BIA hole layout, see the FAQ: Q9: What is the Standard Transom Hole Layout? http://continuouswave.com/whaler/reference/FAQ/#Q9 On the corollary topic of shaft length, the transom on a c.1963 Boston Whaler 13-footer is notched, and the recommended outboard engine shaft length is 15-inches. (See the Reference article on the 13-foot hull for more details.) It is quite good fortune you found a 1995 Evinrude with a short shaft (15-inch shaft), as those engines are hard to acquire these days. By using a short shaft engine on the notched transom, you will be unlikely to need to use any sort of engine adaptor or set back bracket to accommodate the shaft length. Such devices are only used when the engine shaft length is too long for the transom height. That is not the case here.
jimh	posted 11-20-2014 04:12 PM ET (US) Engine mounting bolts that are not in holes with wood reinforcement are not going to work.
jimh	posted 11-21-2014 06:52 AM ET (US) The topic of a curved transom on an older 13-footer and mounting a newer engine with a flat mounting plate is mentioned in http://continuouswave.com/whaler/cetacea/cetaceaPage56.html If you look closely at the illustration (hyperlink below) http://continuouswave.com/whaler/cetacea/cetaceaPage56.html#56-03 you can see the shims that were fabricated to permit a better fitting of the flat surface of a mounting bracket to the curved transom. In this particular instance the mounting used a intermediate bracket to correct for the shaft length problem, but the same sort of approach using shims would work for the bracket of an engine that was mounted directly to the curved transom.
douglasemitchell	posted 11-21-2014 12:10 PM ET (US) Thanks for the Insight..with this info I have plans to make two shims out of 1/2 thick aluminum and bolt engine directly through engine, shim and transom for the two top bolts. The lower bolts have already been drilled(urgh) so most likely use lags as described in this article and possible add two additional bolts trough my aluminum shims for extra strength through the transom near upper engine bolts. clearly i don't see the need for a jack plate since my engine is the correct 15" shaft.. And mounting the jack plate as described still requires the same sort of shims. Jim how do you post pics on this site? Again thanks to all. Dug
dfmcintyre	posted 11-21-2014 01:03 PM ET (US) Doug - (This suggestion may be too late)... Do you have a good fiberglass shop in your area? If so, run the idea of fabricating shims out of glass and epoxy and then painted (or gelcoated) right onto the transom. Could make it look factory. Regards - Don
douglasemitchell	posted 11-22-2014 09:22 AM ET (US) Great ideal. My boat currently has the original gelcoat from 1963 in good shape.. In a year or two I have plans to redo gelcoat. At that time I will look into fiberglass shims and gelcoat. For now just enjoying using the boat. I want reliable power and mechanical all working. Thanks for the ideal. dug