Converting i/o to twin power towers!

[oirebit]

Hey guys. I'm a new member, long time follower of the sight. I just aquired a 1984 19ft Galaxy for a great price...(free)! It came with the 3 liter mercuiser i/o. the engine and drive unit were all taken apart and in the deck of the boat. I'm going to need to repair the transom and replace the stringers. I've already removed all the water logged foam. Do i need to replace the foam? My plan for the boat is to put twin 90 or 115 mercury power towers on it. which would be the better combo? would the 90's be enough power to push it? Thanks in advance guys!

 

[TheWoodCrafter]

Re: Converting i/o to twin power towers!

Welcome to iboats.

We need pictures!!

Changing from I/O to outboard will require some reworking of the back end of your boat. Creating a spash well with the transom sticking up for a motor to bolt to.
Sounds like a project.

 

[tashasdaddy]

Re: Converting i/o to twin power towers!

hate to tell you but 90% of the people who have done this, have not been happy afterwards. all of this throws the center of gravity of one the hull design. put a 4.3 in it and be done.

 

[oirebit]

Re: Converting i/o to twin power towers!

I have heard the good and the bad. yes its true i've heard more bad, but i'm gonna try to make it in the 10% who like it. Its just something i've always wanted to do. My plan is to put a bracket off of the back. That way i wouldn't have to do major cutting out of the transom. anyone think that a single 115 would push it ok? I'd really like to do the twins. Thanks guys!

 

[oirebit]

Re: Converting i/o to twin power towers!

I'll take some more pictures today and post em.

 

[Chris1956]

Re: Converting i/o to twin power towers!

Those 3.0L Mercruisers were 135HP and weighed 600+pounds. That Tower is 115HP and weighs 300pounds. Power should be sufficient. I also do not think the shift in weight will be an issue.

Close up the I/O hole, install a jackplate on the transom, and run the control cables, steering, electrical and fuel lines thru a boot in the transom.

 

[tashasdaddy]

Re: Converting i/o to twin power towers!

you have to remember that the motor bracket is moving the weight further back. the 600 pound of the 3.0 was balance in front the transom. you are now taking about 600 lbs of outboards 18 inches behind the transom. moving back throws the balance way to the stern.

 

[83mulligan]

Re: Converting i/o to twin power towers!

I've seen it done where the splash well and bracket is an extension of the transom that actually floats and supports the motors. Here is a link. it's the "whaler repower" thread. I don't think you can link directly to it.

http://www.glangler.com/letsseeyourrig.html

oops, those were twin seadrives, not an I/O. Sorry. Bracket concept might be something to think about, however.

 

[oirebit]

Re: Converting i/o to twin power towers!

Yeah. My plan is to use a bracket. which is a more reliable engine? the 115 or 90? Does the 90 weigh less than the 115? Thanks guys.

 

[getusummm]

Re: Converting i/o to twin power towers!

Running a single or twin o/b on a bracket should not present too many issues. I would go with a full flotation bracket such as a hermco. Once everything is mounted and running, you may need to add additional weight such as lead to the bow to compensate for the additional weight. You may need to also run trim tabs. I have had a few boats in the past that were conversions and they worked pretty well with fine tuning. You will like the addtional cockpit space and storage gained by going with the outboards and twins will give you additional grunt and extra safety cushion. If one engine goes down, at least you have the second to get back in on. I would probably go the twin route on that boat. I think a single would be taxed too much and get worse fuel economy that the twin setup. The biggest factor is going to be the actual bracket. They are not cheap. Also, you need to make extra sure your transom is up to the task because you are not only adding the weight of the engines, you are moving them back, which is going to give them extra leverage and act like much more wieght and stress on the transom.

 

[oirebit]

Re: Converting i/o to twin power towers!

Oh my transom will definetly be strong enough when i'm down with it. would it be possible to make my own bracket? it doesn't seem like it would be that hard.

 

[tashasdaddy]

Re: Converting i/o to twin power towers!

not a lot of difference in the weight of a 90 and 115, they use the same block.

 

[alumi numb]

Re: Converting i/o to twin power towers!

the new starcraft islander is an excellent example of doing it both ways.
same boat, one i/o and the other o/b.

 

[getusummm]

Re: Converting i/o to twin power towers!

Building a bracket is not overly hard but does require design and fabrication skills beyond the average backyard builder. Remember, your engines are depending on your bracket to hold together when it gets rough. I am pretty good with fiberglass and aluminum. I could build my own, but chose to buy one instead. Its just not worth taking the chance to me. There are several to chose from. D & D marine, armstrong, stainless marine, hermco, and there are several others. D & D is about the lowest cost at $700 for a single bracket with no platform to $1800 for a twin bracket with 8' swiw platform. Hermco is a fiberglass bracket and will not be subject to the corrsion problems that the aluminum brackets have. The aluminum brackets need to have a good quality paint job and it needs to be inspected on a regular basis for paint failures, cracks, etc. Actually the fiberglass brackets need to be inspected also. There are a couple of guys on ClassicSeacraft and ClassicMako that have built theirs using fiberglass. One other thing to look into is the length of your engines. Are they 25"? That is the most common setup for brackets, although a custom bracket with 30" engines would be better, as it would give a little more flotation and get the powerheads higher out of the water. I was running 25" engines and when in rough seas or even backing in moderate seas, it was not uncommon to see powerheads at least partially submerged. Just make sure all your cowling seals are good, lol.

 

[drewmitch44]

Re: Converting i/o to twin power towers!

I have not seen the work in progress but a buddy of mine has done the conversion from i/o to OB and it worked out fine. I have been on his boat 2 times on the delaware bay. The boat was just fine as far as handeling. He did not have a splashwell but he had to mount a beefy bracket off of the transom to hang his OB off of. It is pretty cool though you can stand on the bracket between the motor and the boat that the OB is mounted on. I really like how the boat rides on plane perfectally without trim tabs. He used to have the smart tabs when he had the bravo lower but now he took them off. Just my opinion i believe it can be done.

 

[drewmitch44]

Re: Converting i/o to twin power towers!

And i do not believe for a second that 90% number! I just think that because noone here on iboats has showed a project of converting. Someone needs to do it and post progress here on iboats so we can all see. My buddy has that boat and it has so much space in the stern because of the o/b being outside of the boat. I think its great!!

 

[getusummm]

Re: Converting i/o to twin power towers!

Drewmitch44, I have started a thread titled Master Marine and will post pics, once I get started on it. My boat is a prime example of this screnario. Master Marine is now True World Marine. They offer the same hull with diesel inboard power, single outboard power, or twin outboards on a bracket. My transom is rated for 500hp and came with a single 250 transom mounted in a spalshwell. I will be converting to twin 250s on a bracket. It will probably be another month before i actually get started due to work.

There are many many many examples of converting from single outboards or single and inboards and I/Os to outboards on a bracket. I would say the percentage is probably reversed and 90% are happy with the results. The biggest single problem comes from using a non-flotation bracket. Basically it is an open design and does not provide positive flotation. I would suggest looking on ClassicMako, ClassicSeacraft, GreatGrady, Continuouswave, Whalercentral, or even TheHullTruth for more info on the conversion. The order I listed is by amount of info and relavance to what you are doing. Look for posts by Strict on ClassicSeacraft, and GrantN on ClassicMako . They both built their own brackets along with numerous other repairs and upgrades on their boats. Also look at the projects of Ringleader and WallyJohn for more info on brackets, mounting, and conversions.

 

[oirebit]

Re: Converting i/o to twin power towers!

Would i be better off just getting a single 150 or 200? I think it would be easier and cheaper. but i like the idea of have twins as for the stranded factor.

 

[getusummm]

Re: Converting i/o to twin power towers!

I think cheapest would be sticking with the I/O. You have a full transom right now, so you will either have to modify and cut down the transom and add a splashwell or go with a bracket to mount the outboard. A single 150 would push that boat nicely. The 200 would be even better. That is a 19' boat and wasnt really designed to go offshore. You are probably better just sticking with the I/O or just a single outboard. I have seen quite a few used single brackets for sale pretty cheap. Twin brackets are harder to come by.

 

[sschefer]

Re: Converting i/o to twin power towers!

Personally, I'd keep the I/O and hang a 25hp kicker off the back as my backup.

But if you're he&& bent on destruction then I would go with an off-shore engine setup. This will move the engines back but give you the added floatation to off-set the move. It will also keep your engines in the water better when you need it.
The full setup is a sponson system that is fitted directly to your current transom. If you do it right, you'll have room for a 52 quart cooler also.

Twins off the back will be better than a single because it more closely matches the weight of the current engine. The off shore bracket will add the floatation you need.