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DoughnutToo

twins to single outboard

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I will not entertain this thread on another forum, as it will spin out of control and be a waste of time. My lower unit clutch dog or shift assembly went out on my port engine. I am not going to spend the money to have it rebuilt to cost near $1000. It is just not worth it. I can't find a used one at a reasonable price, most I see are $700-$900. I also need it to be counter rotating, which just narrows the field even more.

 

I have told myself, and my wife, I do not want to replace them with another set of used twins. I would rather have a single 300, but my transom is setup for twin 25" shafts. That means I would need a 30" shaft 300. However, I planned on gutting my transom and pouring a new one when this repower takes place.

 

So, here lies the questions knowledgeable Robalo owners. Do I set out to just purchase a single 300 in a 30 inch shaft, or modify this transom to accept a 25" 300?

 

I can find 25" 300s all day, 30" 300s are harder to come across that are not apart of a triple setup. Or super high hours.

 

Question 2. Power options in 1980 were a single Mercury 300 or twin mercury 150s. Even a picture of a 256 with a single 300. I have only seen one recent photo of a 256 (or 2520) with a 300 Suzuki, but he sold it. I would love to find out how it handled. I want to do bay, inshore and offshore fishing. And by offshore I mean 30 miles in the gulf, not middle grounds. Used twin setups are available for around $7k-$8k. Single 300 $5k.

 

As long as I can get from A to B in a timely fashion, and economically, I am elated. I do not want to do 40+mph. Top speed right now is 37mph with these tired 200's. I would love to see or hear some real world responses. And I do not care about the discussion of twin vs single reliability or security. Not even considering that as an option.

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Post a picture of the transom looking from inside the boat for reference purposes. I just want to see if cutting the transom down to allow the 25" shaft would allow backwash into the wet well when coming off plane.

 

Now you see where I am going with this. I think I recall seeing some boats that had the center cut down to allow the set-up you are talking about. Cut-out looked to be 5 inches....if twins were to be used, the original height was retained to allow 25" shafts to be installed side-by-side.

 

One other idea would be installing a porta-bracket or even consider installing an engine bracket and mount it low enough to allow the 25" shaft to work. Rule of thumb is you drop the bracket down 1 inch for every foot beyond the transom, so this could cause some issues.

 

jack-plate.com has some other brackets that do not have much set-back. May be worth a call to them to discuss what you are trying to accomplish and get their input.

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Here is a picture for you. I have looked at the online brochures for pictures and found a few via google of the single setups. To be honest, I do not want to cut the transom down because I have watched the water rush and hit the transom. If it were five inches lower it would flow in, which I don't want to deal with. Finding a reasonable 30" 300hp in my budget has proven to be more difficult than I thought. Plenty of 200-250hp.

 

There are great deals on twin 225 or 250 hp outboards, but the combined weight is just too much. I know they are over the power rating, which I would never really need that much horsepower, but the weight is just too much. If the Yamaha F350 didn't terrify me, I would consider it as a used option.

post-6302-0-26102800-1502996874.jpg

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I was at work and couldn't finish what I wanted to ask. In reference to adding the bracket, I have been trying to find some solid information. To make it clear as glass, my budget allows for used. I would love to buy new everything, but it will not happen and the wife wouldn't allow. I was looking for a possible single style bracket to put on a 25" 300hp. I like the idea of a full width transom bracket to make climbing into the boat easier from the water, and remove the standard swim platform/ladder.

 

I will be doing a transom pour as my transom replacement when I get the outboard, but I cannot access everywhere for bolts/nuts. Your suggestions on which bracket to go with and how can I tell about being able to use a 25" shaft motor?

 

Edit: And since I have been looking online, I have noticed a lot of 24-28 foot walk-arounds and center consoles with 250hp outboards. Example here, https://miami.craigslist.org/brw/bpo/d/scarab-center-console-fishing/6266184886.html I am curious as to how this thing performs because its base weight is 5500 lbs. Some of these WA's I see weight much more than me and have 225-250hp outboards.

Edited by DoughnutToo

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Dad has a 24' Hydrasport Walk-around being pushed by a 200 Johnson 2 stroke mounted on a bracket. Damn boat will run around 35 on a good day. The only way I can think it works is his boat is 17 or 18 degree deadrise versus my 21 degree. Still, I am amazed it works.

 

Just did a quick check for a 30 inch motor in Virginia and only thing I found was someone in NC looking for a 250-300 hp, 30 inch shaft length. It is almost like trying to find a unicorn!

 

Now....back to my previous post. I must have been drinking that night. Rule of thumb is you RAISE the motor 1 inch for every 12 inches behind the transom...not lower it! Where the heck I came up with dropping the bracket, I dunno. A 30" bracket means raising the motor 2 1/2 inches! I am running a 25" on a 30" bracket and have no issues with backwash.

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Dad has a 24' Hydrasport Walk-around being pushed by a 200 Johnson 2 stroke mounted on a bracket. Damn boat will run around 35 on a good day. The only way I can think it works is his boat is 17 or 18 degree deadrise versus my 21 degree. Still, I am amazed it works.

 

Just did a quick check for a 30 inch motor in Virginia and only thing I found was someone in NC looking for a 250-300 hp, 30 inch shaft length. It is almost like trying to find a unicorn!

 

Now....back to my previous post. I must have been drinking that night. Rule of thumb is you RAISE the motor 1 inch for every 12 inches behind the transom...not lower it! Where the heck I came up with dropping the bracket, I dunno. A 30" bracket means raising the motor 2 1/2 inches! I am running a 25" on a 30" bracket and have no issues with backwash.

 

But when you are talking backwash, you are talking about a standard transom height or cut down in the center? Here is a picture of a 2160 with the center cut for a 25" outboard. Do you have a picture of your transom area for an example? When I was talking about cutting the transom down in the middle, it would look just like this. I would love a bracket and fit a 25" shaft!!!

 

post-6302-0-19911200-1503024862_thumb.jpg

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When I ran a standard transom on my boat (no bracket) I never had a problem with water coming over the transom when coming off plane. Current configuration is not a concern :D

 

 

transom.JPG

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I may end up having to cut down the transom. What are the odds someone can trace a cardboard template of the top of the transom? Like you observed, finding a good 30" is a pain. I also have to remember that if I go with a single 300 at the 550lb area, it is still going to be considerably less than two 200's at 900 lbs and should lift the stern up a few inches.

 

I was reading more on putting on a bracket and have taken into consideration that I don't think this hull will fair well having not been designed in 1980 for one without doing the proper steps. Maybe I should just stick to a transom cut and pour in the Nida Core.

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Wrong assumption on the bracket! My boat an '88 model, and brackets were not even contemplated then. A 21 ft boat is the minimum length that can be bracketed due to the shift in weight. I did a little beefing up of the transom when I re-did mine, adding knee braces on top of the existing stringers so there was more surface area to tie the transom to the stringers and spread the load out over a larger area. I have driven my boat hard since it was redone 11 years ago, and it does not show any stress cracks in the transom.

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That is what i am saying. You took the steps to make sure it was properly braced and supposrted. I am not doing any of that.. I am strictly going to gut the transom core and pour in a new one.

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As long as the poured transom is done correctly so the end result is as good as the original one, you should be fine. The actual fastening points for the bracket to the transom are along the same line or slightly lower than where the engines are currently bolted to the transom. There is already a lot of structural support in that area of the transom. If the bracket is installed with aluminum channel instead of oversized washers for backing plates, this spreads the load out over a much larger area and actually adds stiffness to the transom.

 

On my boat, since I was doing the fiberglass work, I could do modifications "on the fly". The knee braces actually started out as nothing more that extensions to support the floor at the transom where the previous wet well had been located. I had enough coosa board scraps laying around that I said the heck with it and modified my original thought on the floor supports to also tie the transom to a "bigger" stringer area, for lack of a better word. Was it needed on my boat...probably not. I have been told I have a problem where I tend to fix things that are not necessary.

 

Back to my Dad's Hydrasport. His bracket is a Stainless Marine, single engine, bare bones bracket. When I looked into his bilge, the stringers are tied into the transom the exact same way all the older Robalos were constructed. The damn factory install on that bracket has oversized washers (same size as what is used on engine mounting bolts) on the inside of the transom and that is the one thing that really suprised me. Granted, his boat has not been run in as rough water or as many hours of mine, but the washers have not pulled into the transom core and there are no stress cracks. This kinda supports the theory of me fixing stuff that is fine already :yahoo_rotfl: .

 

One other thought on the bracket idea. If you go with a single engine and the bracket, order a bracket for a twin motor set-up with the floatation tub. That is what I did in order to minimize the sitting low in the water at rest issue. Get the biggest tub the bracket manufacturer has! Reason is if you get the swim platform to extend almost all the way across the transom, more surface area to attach to transom, and people like to hang out on the platform at the sand bar. Run the control cables and hydraulic steering through the existing wet well and exit through the transom into flexible rigging tubes. Then make up a drop in cover out of fiberglass to cover the wet well. This concept will make it easy to access the compartment, when necessary, yet have a clean step through when going on to the swim platform through the existing transom notch.

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