Revenge 22 Sterndrive: Conversion to Outboard

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Author Topic:   Revenge 22 Sterndrive: Conversion to Outboard

JesseT posted 02-07-2015 01:54 PM ET (US)
Hi I was hoping to get some extra input. I have a Boston Whaler REVENGE V-22 that had a 350[HP sterndrive]. I pulled [out the engine] along with the outdrive. I just picked up a [Yamaha outboard model] Ox66 250-HP and a new 9.9-HP Suzuki to repower [the REVENGE V-22]. I'm deciding whether to cut down the transom and build a full width splash well out of aluminum and have both engines mounted directly to the transom, or to build an offshore bracket and mount the engine on that. I like the idea of not having the motors all the way back on a bracket, and I would like to be able to run with the plug out of the fish hold and not have to worry about water on the deck. I don't know if the bracket would be able to have enough buoyancy to offset the extra leverage of having the motors farther back and I'm don't really think I gain any more deck space because of how thick the transom cap is. does anyone have any experience with a notched transom versus a whaler drive or better yet a Armstrong bracket static trim? Any help would be appreciated.
Jeff posted 02-07-2015 08:45 PM ET (US)
Save yourself the time and trouble, buy an Armstrong Bracket and install that. It will help with performance and if done well, will increase the value of the boat. If you cut the transom all apart, you are going to greatly reduce any resale you might have.
Buckda posted 02-08-2015 07:23 AM ET (US)
An important consideration:
Boats which are designed to have sterndrive engine propulsion typically do not have a transom that can handle the torque of an outboard motor directly on it. Or, for that matter, and outboard motor mounted to a bracket.
I do not know if whaler changed the transom design for their Sterndrive units. In a sterndrive or inboard powered boat the torque of the propeller is transferred to the motor mounts located under the engine. On an outboard powered boat all that torque is transferred directly to the transom because the outboard is mounted to the transom.
So the first consideration is whether or not your transom needs to be beefed up.
Jeff posted 02-08-2015 12:09 PM ET (US)
Dave,
All Whaler I/O models started the same as the outboard models and then where reinforced to accommodate the extra weight of the sterndrive. The transom of an I/O whaler is more than strong enough to accommodate an armstrong bracket conversion.
JesseT posted 02-08-2015 02:08 PM ET (US)
Thanks for the help. Jeff is correct in that the transom is exactly the same as an outboard hull , it even has the transom cap already finished. There is only a layer of fiberglass on the outside above where the normal transom would end. The only real modification to the transom to mount the motors directly to it would be on the splash well, mainly because it has the earlier well that is lower and tapers from the corners.
Jeff posted 02-09-2015 08:54 PM ET (US)
Here is all the photo documentation Rory Hughes (Whaler27) sent me of his recent refitting of his 32' Boston Whaler Vigilant. They removed the twin 454 I/O's and installed twin 300Hp Yamaha's on an Armstrong Bracket. The boat actually performs better with less horsepower now that it is outboard powered on a bracket.
I was just on this boat on Feb 1 out of Newport CA harbor and it was awesome. Jesse, I would recommend you follow this lead.
https://plus.google.com/photos/103421531781813483446/albums/ 6114024997686051073?authkey=CJCc1bKY0PzumgE
jimh posted 02-12-2015 05:48 PM ET (US)
Your Boston Whaler REVENGE 22 has a full transom. I consider this an asset. It would be wasteful to destroy the rear deck and full transom in order to convert the boat back to a notched transom. That approach is a very bad idea.
Repair the transom from the cut-out for the sterndrive mechanism. Add an engine bracket.
When adding an engine bracket, keep in mind how much floatation the bracket will provide. Some engine transom brackets have a BUOYANCY BOX that provides a lot of added buoyancy to the hull when at rest to help offset the much greater moment arm of weight of the outboard engines move farther aft from the center of buoyancy.
I don't know of any method to predict or calculate how the static trim of the hull will end up with the addition of any engine bracket and two outboard engines, giving consideration to the buoyancy box effect of the bracket.
I have seen some Boston Whaler hulls, in particular a 25-foot hull, to which an Armstrong bracket was added without any sort of buoyancy box on the bracket, and i think the static trim that resulted had too much effect on the hull; the bow tended to rise and the stern to sink.
When Boston Whaler added the WHALER DRIVE they always provided a lot of added buoyancy in the form of the Whaler Drive so that the static trim of the hull was not altered greatly. As I said, I don't know of any method to recommend how you might be able to calculate this effect in advance. It will be a sort of roll of the dice if you add a bracket and take a guess at the buoyancy box needed. But, even with those factors, I recommend you save the full transom design. It would be a shame to modify a full transom Boston Whaler back to a notched transom.

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Author	Topic: Revenge 22 Sterndrive: Conversion to Outboard
JesseT	posted 02-07-2015 01:54 PM ET (US) Hi I was hoping to get some extra input. I have a Boston Whaler REVENGE V-22 that had a 350[HP sterndrive]. I pulled [out the engine] along with the outdrive. I just picked up a [Yamaha outboard model] Ox66 250-HP and a new 9.9-HP Suzuki to repower [the REVENGE V-22]. I'm deciding whether to cut down the transom and build a full width splash well out of aluminum and have both engines mounted directly to the transom, or to build an offshore bracket and mount the engine on that. I like the idea of not having the motors all the way back on a bracket, and I would like to be able to run with the plug out of the fish hold and not have to worry about water on the deck. I don't know if the bracket would be able to have enough buoyancy to offset the extra leverage of having the motors farther back and I'm don't really think I gain any more deck space because of how thick the transom cap is. does anyone have any experience with a notched transom versus a whaler drive or better yet a Armstrong bracket static trim? Any help would be appreciated.
Jeff	posted 02-07-2015 08:45 PM ET (US) Save yourself the time and trouble, buy an Armstrong Bracket and install that. It will help with performance and if done well, will increase the value of the boat. If you cut the transom all apart, you are going to greatly reduce any resale you might have.
Buckda	posted 02-08-2015 07:23 AM ET (US) An important consideration: Boats which are designed to have sterndrive engine propulsion typically do not have a transom that can handle the torque of an outboard motor directly on it. Or, for that matter, and outboard motor mounted to a bracket. I do not know if whaler changed the transom design for their Sterndrive units. In a sterndrive or inboard powered boat the torque of the propeller is transferred to the motor mounts located under the engine. On an outboard powered boat all that torque is transferred directly to the transom because the outboard is mounted to the transom. So the first consideration is whether or not your transom needs to be beefed up.
Jeff	posted 02-08-2015 12:09 PM ET (US) Dave, All Whaler I/O models started the same as the outboard models and then where reinforced to accommodate the extra weight of the sterndrive. The transom of an I/O whaler is more than strong enough to accommodate an armstrong bracket conversion.
JesseT	posted 02-08-2015 02:08 PM ET (US) Thanks for the help. Jeff is correct in that the transom is exactly the same as an outboard hull , it even has the transom cap already finished. There is only a layer of fiberglass on the outside above where the normal transom would end. The only real modification to the transom to mount the motors directly to it would be on the splash well, mainly because it has the earlier well that is lower and tapers from the corners.
Jeff	posted 02-09-2015 08:54 PM ET (US) Here is all the photo documentation Rory Hughes (Whaler27) sent me of his recent refitting of his 32' Boston Whaler Vigilant. They removed the twin 454 I/O's and installed twin 300Hp Yamaha's on an Armstrong Bracket. The boat actually performs better with less horsepower now that it is outboard powered on a bracket. I was just on this boat on Feb 1 out of Newport CA harbor and it was awesome. Jesse, I would recommend you follow this lead. https://plus.google.com/photos/103421531781813483446/albums/ 6114024997686051073?authkey=CJCc1bKY0PzumgE
jimh	posted 02-12-2015 05:48 PM ET (US) Your Boston Whaler REVENGE 22 has a full transom. I consider this an asset. It would be wasteful to destroy the rear deck and full transom in order to convert the boat back to a notched transom. That approach is a very bad idea. Repair the transom from the cut-out for the sterndrive mechanism. Add an engine bracket. When adding an engine bracket, keep in mind how much floatation the bracket will provide. Some engine transom brackets have a BUOYANCY BOX that provides a lot of added buoyancy to the hull when at rest to help offset the much greater moment arm of weight of the outboard engines move farther aft from the center of buoyancy. I don't know of any method to predict or calculate how the static trim of the hull will end up with the addition of any engine bracket and two outboard engines, giving consideration to the buoyancy box effect of the bracket. I have seen some Boston Whaler hulls, in particular a 25-foot hull, to which an Armstrong bracket was added without any sort of buoyancy box on the bracket, and i think the static trim that resulted had too much effect on the hull; the bow tended to rise and the stern to sink. When Boston Whaler added the WHALER DRIVE they always provided a lot of added buoyancy in the form of the Whaler Drive so that the static trim of the hull was not altered greatly. As I said, I don't know of any method to recommend how you might be able to calculate this effect in advance. It will be a sort of roll of the dice if you add a bracket and take a guess at the buoyancy box needed. But, even with those factors, I recommend you save the full transom design. It would be a shame to modify a full transom Boston Whaler back to a notched transom.