1992 Sea Ray Sundancer 290 Outboard Conversion Project

thesaintlyone

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As Suggested I have decided to start another thread that I hope others will find useful. re Converting a 1992 Sea Ray Sundancer that I purchased for £5000 to outboard power. That I hope others will find useful.

43563688930_cb4252c607_b.jpg

Disclaimer: if you feel the need to tell me what a bad idea this is and suggestions of selling the boat there is another thread please go find it. Constructive criticism and comments are welcome of course but this is a project and if it doesn't work then that will be a lesson learned please remember we dont all by boats to sell em. That Said...........

Converting a boat to outboard power is not a new thing and has been done successfully by many people the world over.

https://www.wavetowave.com/home/2018/1/17/outboard-conversion-repower


For Me Personally There are a number of reasons I chose to go with Outboards:

1) Cost - Re powering (Converting) to Outboards is potentially a cheaper option than installing two stern drives the most significant cost involved depending on your choice of outboard is the Outboard Pod or Bracket conversion its self. Brackets and Pods are available from Armstrong and Porta Bracket for around £2000-£4000 which is the cost of one single engine.

2) Up-gradeabillity - Related to cost my initial uses for this boat beyond the fact that I will be using it as a stay aboard on the river Medway will likely be river cruises up and down the Medway as far as Stangate which is a great little overnight creek just before the Medway reaches the Thames estuary and longer cruises in the Thames estuary and up to the far reaches of the Thames its self. This means that initially I can purchase outboards that whilst not giving the out an out planing power normally associated with these boats once a suitable pod/bracket is in place I can upgrade as needed later.

3) Ease of Maintenance - I am no mechanic but I know a few that are and the ability to unhook an outboard and take it to the repair shop is a much more attractive prospect than squeezing about in engine bays. and if the worst was to happen replacing an outboard is a much easier prospect.


So On to the project itself. for me there are a number of considerations involved in choosing how to go about this and which Pod/Bracket style to go with:

1) Aesthetically pleasing - I want it to look good, the idea of just bolting some contraption on the back and moving the boat forward is not my idea of fu I want this outboards to look good like is was meant to be there.

Formula+350+CBR.jpg

This formula 350 CBR is probably the closest representation of how I would like the conversion to look where the Pod/Bracket sits hidden under the swim platform

2) Single or Twin Outboards - There are alot of good arguments for one or two outboards and I am currently undecided on which

3) Full functionality - The integrated Swim platform of the Sundancer as shown in the picture of my boat above does present its own problems with design as the Pod/Bracket must be mounted underneath and clear so that the outboard still sits and moves as it should

4) Strength - A few conversion projects have used a brace system from the pod to the existing stringers in the old engne bay itself to provide extra support for the transom.

5) Which Pod or Bracket Design - The Pod must be able to hold big enough engines for the upgradeabillity mentioned above Here are a few links to what I've already found.

Porta Bracket
http://www.portaproducts.com/index.php?page=56

Stainless Marine
http://www.stainlessmarine.com/prod...utboard-engine-brackets-twin-engine-brackets/

I'll be posting plenty both here on a blog and hopefully youtube as the project progresses

Regards
 
Really interesting project, and something that I will keenly look forward to updates on. :cool:

I suppose a starting point would be the boat dynamics. Even if you are starting as a river cruiser you mention that you intend to design in a future proof upgrade for more power etc.. And I think this is going to be the tricky part.

Obviously, more power = more weight which hanging further away from the CoB/G could be the trickiest part of the problem to solve. Once an idea of this, your outboard bracket etc has to fit this solution along with transom adaptation and strengthening.

With respect to costs, I would probably accept that you are not going down a 'cheaper' route for repowering. Looking ahead at your future proof route, you will need two outboards of the same spec - That's a difficult proposition in itself used. A costly one new obviously.
Shooting from the hip, I would budget 10k for river cruising and upgrading to twins with >HP 20k based on acquiring some outside help.

Lastly, also accept that this boat may be uninsurable through normal routes. Something to think about if you intend to hang some nice 200s off the back! ;)
 
Im Following this with interest, keep the updates coming.

Converting to outboards looks like it should be a simple ish job, but interested to hear the reality
 
Some thoughts ...

1. before you start see if someone on here or a web resource can tell you the impact on stability / riding angle. Removing huge amounts of weight from the middle (ish) of the boat and moving it all back could well gives rise to something that rides so bow high as to be dangerous / unusable.

2. I didnt follow how the bracket worked on the second link, and the first seems complex with hydraulics ( the outboard will have power tilt I assume).

Given the cost is a large % of the original purchase and you are doing this for you and not resale, getting a stainless fabricator to make something may be cheaper ( might not) and might fit better.
 
The Future Proof Part of it really relates more to the spec of the Pod/Bracket in that there are cheaper alternatives but they are limited to a Max HP. This one advertised on Ebay for example is limited to 120HP

https://www.ebay.co.uk/itm/outboard-mount-pod-gill-bracket-grp-for-upto-120hp-ideal-outdrive-covertion/152994816484?hash=item239f33a1e4:g:ZVsAAOSwEmlZ1RrL:rk:1:pf:0

Im not sure how much Im going to require more than 120HP even in the future but its nice to know.

This does beg a question??? How Much power do I really need???

I'm building this boat for myself not for Joe Blogs 10 years down the line. What kind of power does a Sundancer 290 need to blast up and down the Thames how fast can one really go or want to go responsibly go. These boats tend to have bigger power plants cause they were built for the american market where there is alot more room.

In terms of it being the most cost effective I am referring to the initial cost outlay to actually get on the water which can be done with smaller outboards initially.

Thanks for your imput
 
I had a Cranchi 33 Endurance, so a bit longer. It had 2 KAD300s in it. 285 each so 570hp. 2 x 120hp = 240 which would seem a bit light.

If you repower later bear in mind this will likely require new ( of some combi of) instrumentation, throttles, steering mods. You then need to dispose of the hard found matching pair and find another.

Just do it once. It will cost less in the long run.
 
This does beg a question??? How Much power do I really need???

Its a big heavy boat. I think you will need 100 hp to river plod comfortably and probably 350-400hp to obtain some good performance.

Strapping on a 100hp is probably doable cheap, with little engineering judgement and most likely you will get away with the weight balance issue.
350-400hp is a different kettle of fish. The mounting arrangement to transfer that sort of horse power to your boat is probably going to have to be custom made and it'll add more weight to aft of the transom. The fuel tanks may have to be relocated in the anchor locker!
 
Some thoughts ...

1. before you start see if someone on here or a web resource can tell you the impact on stability / riding angle. Removing huge amounts of weight from the middle (ish) of the boat and moving it all back could well gives rise to something that rides so bow high as to be dangerous / unusable.

It depends on how much smaller outboard(s) weigh compare to the engines/outdrives. The old engines aren't middle(ish) they are at the very back of the boat. The outdrives already stick out the back of the boat. My guess would be it wouldn't change the balance too badly and he can always add ballast forward if it is too bad.
 
often thought about how viable/successful a project like this would be. such a wide range of outboard power options and even more so now with the soon to arrive 300hp diesel outboard from Cox.

Could a central section of the bathing platform be cut out (with side sections supported or reinforced) to make bracket and outboard mounting easier?
 
It depends on how much smaller outboard(s) weigh compare to the engines/outdrives. The old engines aren't middle(ish) they are at the very back of the boat. The outdrives already stick out the back of the boat. My guess would be it wouldn't change the balance too badly and he can always add ballast forward if it is too bad.

I have a shaft drive so you are most likely correct.

However you are still making large changes in weight and by moving it back amplifying it’s effect. I would rather work it out now than find big issues later.

Even production boats have issues. Manhattan 56 huge rear skeg. Putting a Willaims 325 on the platform also has a surprising impact c
 
I have a shaft drive so you are most likely correct.

However you are still making large changes in weight and by moving it back amplifying it’s effect. I would rather work it out now than find big issues later.

Even production boats have issues. Manhattan 56 huge rear skeg. Putting a Willaims 325 on the platform also has a surprising impact c

Still very much in the planning stages to get everything right ?
 
often thought about how viable/successful a project like this would be. such a wide range of outboard power options and even more so now with the soon to arrive 300hp diesel outboard from Cox.

Could a central section of the bathing platform be cut out (with side sections supported or reinforced) to make bracket and outboard mounting easier?

That was suggested by a professional who does a dozen or so Conversions per year
 
Given I categorised this project as “madness”, I guess I have to get onboard with the mad idea and see where it leads.

Apart from where the bracket goes, a fundamental decision will be “planing” (needs lots of hp) or “displacement”.
For displacement, I don’t see that much more than 50hp would be needed, and this would have the advantage of less weight hanging out of the back.
Also, you might be able to shift batteries forward to compensate a little.

Cutting the bathing platform and getting the outboard as close as possible to the transom would definitely help with weight distribution.
 
I've just received the following from my enquiry to Porta Bracket. Which does suggest cutting into the swim platform to be the best bet. Done properly I can't see why this wouldnt end up looking really nice

Hi Duncan,

To effectively use all of the travel the Porta Bracket has to offer you would need to remove the platform in the area the outboard and bracket would move through to operate. This would leave you with two separate platforms on either side of the motor. If a retrofit like this suits you, please provide motor shaft length and number of outboards you're going to use and we will recommend a model #.


Kindest regards,
Scott Porta
 
Thanks for the reply, Are you saying that an outboard of 50hp would create the planing effect. The Size of outboard is something I'm still contemplating. I want a mix of reasonable performance and reasonable economy. I dont consider myself someone who wants to get it to go as fast as possible but rather just Motor at a nice speed with a little in reserve ?
 
Thanks for the reply, Are you saying that an outboard of 50hp would create the planing effect. The Size of outboard is something I'm still contemplating. I want a mix of reasonable performance and reasonable economy. I dont consider myself someone who wants to get it to go as fast as possible but rather just Motor at a nice speed with a little in reserve ��

For the boat to get up on the plane with twin outboards I would think a minimum of 2x 125 would be needed, probably 2x150. With a single outboard you might just get away with 1x 225. Although I would want a single 300 as I mentioned in your other thread. A 50 will give you a max speed of around 8 knots if you are lucky.
 
Thanks for the reply, Are you saying that an outboard of 50hp would create the planing effect. The Size of outboard is something I'm still contemplating. I want a mix of reasonable performance and reasonable economy. I dont consider myself someone who wants to get it to go as fast as possible but rather just Motor at a nice speed with a little in reserve ��

What you want is simply not achievable and surprised you have not worked that out already. If you want planing performance you have to replicate the original power - not exactly but in the range that the boat was designed for.

If you want displacement speeds a 50hp would do it easily, but what you end up with is a boat with severely limited capability. A lousy displacement boat - hull was never intended for displacement work - and not capable of doing what it was designed for.
 

Other threads that may be of interest

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