Conversion and Restoration OMC Stringer to Whatever

[Guest]

Noobs:

That 305 will mate up to just about anything.
If I were you, I would go with a MerCruiser Alpha Gen 2. These drives are rated to about 300 hp and there are literally millions of them around. They are the most common stern drive out there and have some very good design improvements over the Gen 1. Because of their commonality, you can get, [parts are plentiful and cheap (as sterndrive parts go) Lots of aftermarket stuff too from companies like GLM, which will save you a lot of money over OEM Merc parts. Just make sure that the drive you buy has the gear ratio for a V8. You can also save money on used parts like the mounts, pump brackets and bellhousing. You can get a complete aftermarket Gen 2 outdrive, Brand new with warranty from places like Sterndrive Engineering. The skies the limit.

 

[zool]

Personally, I would take the VP 290 over most Mercs, they are bullet proof, inexpensive to buy nowadays, and relatively simple to work on, but like Erich said, you need the correct ratio, for a single prop 290, its 1.61:1...

I believe its 1.78:1 for duo-prop lowers on v8s

with a donor setup you will also get the transom shield and v8 flywheel cover/pds, and y-pipe.

 

[Bondo]

My chevy 305 block is a 225 hp by the way, V-8. I think its the same motor from the '78 Chevy Camaro, in a marine version.

Ayuh,..... Sell it, 'n buy a 260 hp Merc Alpha 1, or a newer Gen.II,....

While some of the Volvos are abit more desirable, the Merc you can get fixed, or buy parts for, 'bout anywhere on the planet,....

Ya want to use the entire driveline from the donor boat,....

Sell yer's to somebody tryin' to get one more lap, outa their ole OMC,...

 

[RiverNoob]

Howdy!
Didn?t get as much done as I wanted this weekend, my full face respirator and Tyvek suits didn?t arrive yet. So not as much saws-all work as I would like really happened.
Got some pics though:
http://s952.photobucket.com/user/RiverNoob/library/Columbian

Now, in the photo, ?Transom Keyhole Wood? you see that beam underneath the blower hose in the center of the pic? 2 of these on each side,, I didn?t think this was one of the stringers, the motor was mounted on these,, I thought it was just a motor mount, and the stringers run next to the walls on the sides of the boat. Am I wrong about that? Is this actually a stringer in the photo?

Also, was talkin to some friends bout it, and it seems like converting to an outboard would be a better way to go. I have found several 200 hp plus outboards from 1998 ? 2006 that were in the 3500-4000 dollar range, some Yamaha salt series, and I want this boat for offshore too, near mouth of Columbia river. It seems like outboard will be easier to do swaps later, will be more accessible to do maint, and work on, provide more space on the deck, and I could save money to buy one while doing the other stuff. Since wood, glass, and epoxy aren?t really very expensive by themselves. The brackets I have found for about $1,000 for the one with a 250 hp main and a kicker plate. And a newer I/O setup, which I think I would want instead of older models, is actually nearly the same price really. Especially a reman engine with warranty and newer model outdrive. Volvo setup newer would prolly be more than outboard setup with used outboard motors.
I can then also get a nicer, newer outboard 3-5 years down the road. And could also possibly just build the bracket with aluminum sheet and bolts and then paint it. I saw a boat on iboats which had that.

Also, I need a 20-30 hp kicker for trolling, and as auxiliary/backup if I go out toward the tuna fishing grounds over here. So I would need at least a kicker plate on the back anyway. I don?t want to go out there without a backup. Even if the main motor is brand new I don?t think I would. Its 15 +/- miles away from land?.. breaking down would suck with only one setup.
I know Zool mentioned I/O re-power was safer, and others seem to think I/O was a better way to re-power.
Am I just thinking about it wrong? Or can I do the outboard job? Is it extensively more complicated?

Also, with converting to an outboard,, can?t I just build up the transom to like a foot thick with extra bracers on the sides, over-do it, and then bolt a bracket on- taking care to align it perfectly centered, and at the correct height for the types of outboards I want to get?
What do we all think about this?

Sorry for writing a small book.

 

[jbcurt00]

If this 'beam' extends forward past where the motors dog house was, then it is both a motor mount and a stringer.

I'd suggest you follow Bondos advice and find a donor boat w a running 260hp Mercruiser and swap all its components to your hull.

Not sure why you're comparing prices of newer reman'd I/O motors to used outboards. Are those $3500 big hp outboards rebuilt powerheads and lower units? I havent shopped for one, but would be leery of used outboards that have been used in saltwater.

IMO, bolting a bracket to the transom is a much more complicated process then some make it out to be, thats why engineered brackets run 1K.

I copied the IMG code to copy/paste your pix into my post

Good luck w your project

 

[Scott Danforth]

as many indicated, find a donar boat for the driveline from prop to pullies. then rebuild your transom and stringers and engine mounts accordingly.

you have to rebuild the transom anyway, as the OMC required a hole in the transom large enough to drive a golf cart thru.

a properly engineered outboard bracket and transom repair will cost more than the simple transom repair to put in an I/O. For $3500-4000 I can build a 383 stroker with a supercharger on it, or build a healthy 350 and put a new drive on it. when looking at outboards you will get someones used outboard for that price as you indicated. I think you are overthinking this. fire up the tools of desctruction, remove the transom wood and stringers up to the next bulkhead and start rebuilding it. Inbetween itch sessions, find a donar hull and strip out the driveline, controls, etc.

 

[Guest]

Noob:

You sound like you're exactly at the same place I was, when I started my second Hiliner Restoration. I had just repowered the first boat from an OMC stringer drive to a Volvo SX drive. I can tell you this from experience doing it both ways. The Outboard conversion is EASIER.

When you consider rebuilding the transom, which you will have to do either way; with a sterndrive, you have to take extra care in cutting the keyhole for the replacement drive. This requires templates and other information that must be done right the FIRST time. When I got the installation instructions for my Volvo, which most dealers and Volvo themselves are reluctant to give folks like us, it involved some pretty precise measurements when locating the gimbal housing on the transom. If you mount it too high or too low, (This determines your outdrive height) you're stuck with it because getting it wrong requires rebuilding the transom again to a certain extent. You then have to deal with alignment issues between the engine bobtail and the gimbal, engine height inside the boat, etc.

I'm not saying it can't be done, I did it and was lucky enough to get it right, but it was by no means easy.

On the second boat, which was a center console anyway, I chose to close up the OMC stringer hole and rebuild it to a 3" thick outboard transom. For the stringers in the stern I glassed in (2) 1" oak Knees that fastened the transom to the stringers. Now the transom is solid on its own merit, but glassing it to the stringer gives me a solid structure with absolutely no transom flex whatsoever.

I bought a freshwater Used 200 OceanPro and bolted her right up with no fuss, You can adjust the proper height during installation and you're free from all those complex alignment issues with a sterndrive.

That photo you posted certainly brings back memories...More than Once!

 

[RiverNoob]

CaptErich,

Exactly what I was thinking when doing research,,, it really seems like the outboard maneuver will be easier, and have less opportunity for me messing it up,, even though it will cost slightly more up front to get my initial short term cheaper outboard, and then cost even more 2-3 years later for another newer model once I'm convinced the conversion went well. So I think I've decided I'm going this route....

I actually want to learn everything I can in my lifetime about boats, so I'm sure I'll have the opportunity to do this again sometime and try out a I/O swap. but for now I'm more comfortable trying out the outboard mission. I always say, go with what yer feelin, right?

Do you have pics or a thread of the one you did?
also,, it sounds like you just built up the transom and bolted on an outboard, no bracket used. Is that what I'm gathering?

My plan right now is to embark on side mission and buy a welder and teach myself to weld, (with the help of a couple friends I know, with the experience) and then build a bracket myself.
I drilled a guy who does it already with questions and already know the basic design of how he does it. Sounds like the proper method is to create a bracket that is a formed/shaped extension of the bottom of the hull out, up to the proper height you want the motor to sit, depending on the shaft length you will look for, and then bolt it through with sealer to a backing aluminum bracket with bracers going to the stringers like you said. That way it extends the hull and your back end won't sit lower in the water like with the older style brackets.

but it sounds like you avoided the bracket altogether,, you got more details on that?
the transom on my boat is about 5 to 5.5 feet from the bottom of the hull,, will that pan out the way you did it, or do I need a bracket?

 

[RiverNoob]

There is one thing I forgot to mention,, part of the reason I also want to go with the outboard is to extend the motor weight out a bit, slide the gas tank back a bit, and then raise the deck where the windshield is back just past the steering wheel cockpit, and then I can sit higher while driving (this boat seems to have a hulking bow) and can see better over the bow, and can also extend some cuddy room back, put in a little head area (I prolly won't do the plumbing, just a port-a-potty area really) and then another little mini fridge and perhaps a table, for added amenities..... I want to use this boat for one-nighters in the Columbia River also If I could set it up good enough.. Salmon/steelhead fishin' and then break to Pikeminnow fishin for extra cash (that's a bounty fish over in my neighborhood if you aren't aware).

So I might be an idiot and doing the wrong thing, and just want you guys who are experts and think the I/O is the right way to go, no offense or anything. You might be totally right and this will end up being one big mess just because I'm stubborn.... but I'd still appreciate your input with the outboard work,,, if it becomes a nightmare it will just be my own fault and I can accept that,,,

Thanks everybody,,

 

[zool]

Search the threads here, river, there a a few bracket installs, and even some homemade ones, some were successful, others, not so much. It is gonna take a bit more engineering to hang a big OB on a bracket, as opposed to just notching out a transom..and shifting the motor weight 2-3 feet aft, and also the fuel, the boats gonna sit and plane differently, but maybe that can be compensated with the aft cabin idea u have...and/or trim tabs

I know the guys on the Mako and Seacraft forums do some bracket installs too.

Ill follow along and try to help if I can, I just might not take the maiden voyage is all

 

[MTboatguy]

LOL, Pikeminnows, that is funny, when I was fishing them, we called them squaw fish on the Columbia and we used them for fertilizer for the garden, that was before they started paying bounties on them.

 

[RiverNoob]

haha,
where's your sense of adventure zool?

It's cool, I'll be alright, I have several friends with boats, and there's almost always at least 1 or 2 of them in the Columbia when the fish are runnin'
so I will have witnesses if the motor falls off, and will just collect insurance and move on. but I'm gonna do my best to make 'er seaworthy.

The maiden voyage and probably the first 20 voyages will only be in the mighty Columbia river. Ain't goin offshore til I'm confident the job took hold.

 

[RiverNoob]

Yeah, I always called them Squawfish too. But someone decided that's not politically correct. (very nearly anything you say isn't anymore)
so I always say pikeminnows when in public or on the net n such.

but when keepin it friendly, yeah, They were always called squaw's before. the bounties are high enough you can have fun fishin' n sometimes bring in an extra couple hundred on the good days.
I know people claim they have $1000 and $1500 days sometimes. but that's prolly with getting a tagged one or two, they are worth $500 each.

 

[zool]

haha,
where's your sense of adventure zool?

It's cool, I'll be alright, I have several friends with boats, and there's almost always at least 1 or 2 of them in the Columbia when the fish are runnin'
so I will have witnesses if the motor falls off, and will just collect insurance and move on. but I'm gonna do my best to make 'er seaworthy.

The maiden voyage and probably the first 20 voyages will only be in the mighty Columbia river. Ain't goin offshore til I'm confident the job took hold.

ha, Im just poking at you river, im sure it will turn out fine..I was an offshore junkie for a lot of years, I once fished a 12' glass gamefisher 1/2 mile out the inlet, drifting for fluke lol...when I finish my current project, im sure ill be right back on the tuna grounds...

 

[Guest]

Just to clarify, my outboard conversion was a conventional notched transom. I never really cared for single outboard brackets because I never liked the way they looked and when your off plane, the powerhead of the outboard rides in the stern wave coming off the back of the boat. I've also seen power heads fully immersed when backing down on a fish in rough water. Twin bracket outboards don't seem to have this problem because they are offset from the centerline of the boat, (the deepest part of the hull. As a result, the power heads are mounted higher on the transom.
Since this is your first boat and if you're Hell bent for a bracket, I would not fabricate one myself, just a buy a pre-fabbed bracket such as an Armstrong. There are lot of static and dynamic loading on a transom, not to mention the physical moment placed on a transom when bracket mounting an outboard. This type of structure is not something that you "try out", because it can be dangerous. Buy a bracket that has all the engineering calcs worked out, or you'll be constantly "looking over your shoulder"
A home made one will surely fail at the most critical moment, and you can't pick a worst place than the Columbia River Bar for that to happen.

 

[RiverNoob]

I'm not really hell-bent on bracket,
I would just much rather do an outboard on this boat.

Do you think this can be done without a bracket?
can a notched transom be done, or other modification?

 

[zool]

I'm not really hell-bent on bracket,
I would just much rather do an outboard on this boat.

Do you think this can be done without a bracket?
can a notched transom be done, or other modification?

We really need to see a pic of the transom on your boat to give an opinion on a notched transom and splashwell fabrication....and even if its doable, they can be troublesome offshore, especially in a following sea..

Hard to beat a full height transom with either inboard, I/O, or bracketed OB in the big water...

 

[RiverNoob]

Well I don't want to completely rule out possibly good options,
I just really like the outboard situation, it's not set in stone I suppose, there is still a lot of time in between to think about things.
what do you think about a direct drive inboard with this boat, zool?
too difficult?

you can see the transom in the pics I posted to photobucket in the link I put in prior post,

is there something else you need to see better in a pic? you want an outside larger view pic, or inside larger view one or something?

 

[RiverNoob]

this one
http://s952.photobucket.com/user/Riv...rary/Columbian

 

[Scott Danforth]

while your jumping from I/O to outboard to now direct drive, why not consider going to surface drives or jet drives while you are at it........