Outboard conversion

E02A634A-F79E-49F0-BD26-007E2B387B88.jpeg
 
Awesome! (Or is that a photoshop?) That looks great who built the engine mount, or were you able to buy off the shelf? What size/make outboards did you go with? If you are willing I would really appreciate any details you can provide about the cost, conversion issues, transom reinforcement, etc.
What us your fuel consumption?
 
DE2B686E-7D31-492F-B63F-8D122D2C9D04.jpeg
5CCF6D12-B3E8-4CED-B3C2-87C315D7759A.jpeg
This is the final product for sure. I had a local fabrication guy named John Borlán custom make the bracket. I mounted twin 225 optimax motors. The bracket has a 36” setback for the motors and is roughly 8.5’ wide. Real world fuel economy is about 1.35-1.5mpg at 28-30mph in 2-3ft seas. Right now I’m running turning point 4blade props 15x15. I’m getting 5500rpm wot at 41mph. The motors are mounted a bit high (3inches higher than the bottom) as they are blowing out when trimming up passed 1/3 trim. I’m going to drop them a hole when she comes out of the water. I’ll post a photo of the interior of how I beefed up the transom. I glassed in knees and had gussets also fabricated above the knees for extra support. It was overkill the route I went but the setup is good for triplets in the future. I sold the i/o powers plants with the b3’s which paid for the outboards. The bracket was 5,000 installed and had the motors mounted at that time. I did everything else from the fiberglass work to the rigging. So out of pocket I spent maybe 7,000. What I learned from this is even though the motors are set way back the semi flotation bracket provides a hair too much flotation which only shows during an at rest state.
 
Someone told me (paraphrasing) “for every 12” you move the engines back, the prop needs to come up 1 inch” (I don’t recall the exact numbers, could have been 6 to 1). So, I’m guessing the b3 props were about 6-12” below the bottom? Of course, this calculation is for an outboard boat that you are adding an engine mount to, so not apples to apples. Sounds like if you had to replace the manifold/riser/elbows a few times, you’d be even. And you can’t top the reliability and ease of maintenance or upgrading. The optimax engines are 2 stroke right? I think the 2 strokes are a bit noisier than the 4, but maintenance seems to be better, and I think the extra torque (in the low rpm range) you get from a 2 stroke compared to the 4 should help on a larger boat as well.
Regarding the flotation, if you add weight to the inside of the mount, does it sit better? Like fill it partially with water or something?
Congrats, and enjoy..
 
I was shooting for the every 12 inches back moving the cav. plate up 1 inch in compairison with the bottom of the boat. With the way the hull rides the 3'' rise is an inch too much so down they go when she is laid up for the season. It definitely works now but could be better for more trim purposes. You absolutely right about being even after a eliminating a couple manifold changes. It's nice not having to worry about those anymore. The optimaxs are two strokes. They make a little more noise than 4 strokes of the same HP. I know at idle they certainly make a little noise and at WOT you can hear them roar. I'm liking the fact of no more oil changes again! Just add to the reservoirs and go. And your right about the low end torque, it gets right up and goes. When I launched the boat I had ballast in the boat where the I/O's previously lived (600lbs) and it sat better but still a hair stern high. I dumped the ballast during the initial sea trial because it's useless to have all that dead weight anyhow. I did fill the bracket to the an equal librium water level to see the affect and at rest the boat sat how it did with the I/O setup. Once the season is over I'm going to have the bracket guy chop the bracket to rid a significant amount of the flotation. It's all good for now. Water still sheds to the stern and we are able to get the boat into some skinny water at the sandbar and not have to worry about the I/O's.
Someone told me (paraphrasing) “for every 12” you move the engines back, the prop needs to come up 1 inch” (I don’t recall the exact numbers, could have been 6 to 1). So, I’m guessing the b3 props were about 6-12” below the bottom? Of course, this calculation is for an outboard boat that you are adding an engine mount to, so not apples to apples. Sounds like if you had to replace the manifold/riser/elbows a few times, you’d be even. And you can’t top the reliability and ease of maintenance or upgrading. The optimax engines are 2 stroke right? I think the 2 strokes are a bit noisier than the 4, but maintenance seems to be better, and I think the extra torque (in the low rpm range) you get from a 2 stroke compared to the 4 should help on a larger boat as well.
Regarding the flotation, if you add weight to the inside of the mount, does it sit better? Like fill it partially with water or something?
Congrats, and enjoy..
 
I saw your boat In Oak Bluffs last weekend. I was impressed and meant to stop by to tell you so. The name on my boat is 3D we are usually on 11 row. Please stop by next time. I was getting ready to post here about ur boat. I'm glad you did first.
 
I saw your boat In Oak Bluffs last weekend. I was impressed and meant to stop by to tell you so. The name on my boat is 3D we are usually on 11 row. Please stop by next time. I was getting ready to post here about ur boat. I'm glad you did first.
Saw y'all there rafted up when we went to the beach with the little one. Hoping to get back there in a couple weeks or so. If I see you I'll definitely stop by. Those storms that rolled through were something else. We were watching the clouds from Nancy's while waiting for our mudslides thinking that doesn't look good. As soon as our drink where ready we ran for the dinghy and hit 2' slop in the harbor heading back to the boat. We managed to get to the boat without spilling a drop of our drinks!
 
We have recently redone our cockpit and I have just finished rebuilding our cabin on our 2000 Sundancer 270. We have built in a bar back lot with LED’s, ripped our walls and carpet added sea deck everywhere and live our boat but after rebuilding the I/O’s multiple times because of the corrosive salt water environment, we are over it. We are getting ready to put a pair of outboards on her. I really enjoyed seeing your project. I will PM you to pick your brain a bit more if it is ok.
 
We have recently redone our cockpit and I have just finished rebuilding our cabin on our 2000 Sundancer 270. We have built in a bar back lot with LED’s, ripped our walls and carpet added sea deck everywhere and live our boat but after rebuilding the I/O’s multiple times because of the corrosive salt water environment, we are over it. We are getting ready to put a pair of outboards on her. I really enjoyed seeing your project. I will PM you to pick your brain a bit more if it is ok.
Someone on the FB Club Sea Ray did it to their boat as well, although, could be the same person, but if I recall, it was a different boat. Good luck, and let us know...
 
Thanks, I will include some pics and technical help as I work through this major project. First step is I need to find a trailer I can buy or borrow so I can get her off the water for a while. Some of my friends have done this with their speed boats and the concept isn’t much different. I do like how Jgren used optimax 225’s and they were enough for his 29’ Amberjack. The 225’s are a serious option for me and now I know they will be enough power. However my first choice would be a good pair of Verado 250s, if I can find a deal.
 
Thanks, I will include some pics and technical help as I work through this major project. First step is I need to find a trailer I can buy or borrow so I can get her off the water for a while. Some of my friends have done this with their speed boats and the concept isn’t much different. I do like how Jgren used optimax 225’s and they were enough for his 29’ Amberjack. The 225’s are a serious option for me and now I know they will be enough power. However my first choice would be a good pair of Verado 250s, if I can find a deal.
Go to FB, join Club Sea Ray group if you are not already, search Outboard conversion. Lots of pictures...Alexander added twin 350 Yamahas to an Amberjack, cleaned up the bilge, engine mount added below the existing swim platform, so entire swim platform remains, added aluminum braces from transom to stringers to ensure the engines are supported. 54mph at 6100rpm and cruising around 30mph at 4200rpm, new props, 24 pitch Bravo 4-blades. 58.7mph top end at 5500rpm and 30.2mph at 3500 rpm.
 
This is awesome. For all who mention cost effectiveness or why do this…when has buying or having a boat been a financially prudent thing in the first place, lol. For me, I’m attached to my boat for sentimental reasons, plus I really love my particular model, plus I’ve put money into other upgrades and fixes over the past couple of years, so going this route wouldn’t be a ridiculous idea - no more than having new canvas at $6k on a 30+ year old boat that at best is worth $10k. The only reason why I hesitate is because I’m in freshwater so we don’t have the issues salties have to deal with an a 260 Merc/Alpha 1 pretty much last forever with proper maintenance. Even at around $20k, for a single, used 300, this route would be a serious consideration, especially if your drivetrain is causing issues or at the end of its lifecycle.
 

Forum statistics

Threads
112,950
Messages
1,422,861
Members
60,932
Latest member
juliediane
Back
Top