OMC 4.3L HO with cracked block

[Lou C]

It's really impossible to estimate the total cost because it varies based on how much you do yourself and if you have to have a shop do any of it, and even what materials you use (ie poly vs epoxy resin, standard exterior plywood vs marine, etc). Engines will similarly vary. One can pay up to 2500 or so for a professionally rebuilt pre-vortec V6 which is what you have, or substantailly less. Due to the age of the old pre-vortec models, the chance of finding a good one is not great. Vortecs are more common but there are differences that have to be taken into account. Scott can expound on that further. I can tell you with all new parts, the exhaust conversion cost me about $1200, about 700 in change for the manifolds and elbows, the rest for the Volvo Penta exhaust tubes, hoses and clamps. A pair of re-man heads was about $550, a gasket set, about $125, I also replaced all the head bolts due to corrosion (forgot what that cost, maybe 40 bucks?). A rebuild kit for the Q-jet was about $50, it goes on. The total parts cost for my top end engine overhaul (block was still good) and new exhaust was a bit over $2000 parts plus my labor.

I can tell you one thing, any boat I put my life in, I am sure as all get out not putting a junkyard engine in! I boat on Long Island Sound and I no longer have tolerance for break downs. When its time for another engine, if I keep this boat (doubtful) it would have to be NEW. No more old junk for me. It is hard even to find good machine shops anymore.

The question to ask yourself, do you want to have a boat to use (then don't do this!) or do you enjoy learning these skills and can live with not using it till its done (most of us). Once was enough for me though, This even cured my longing for a collectable car because unless you buy one already done, its more of the same as boat restoration, I'd rather get a late model muscle car that gives me some of the same feeling. I got sick of finding parts no one makes any more, fixing every single thing myself, etc. I'm semi retired but even so, there are other things to do in life!

 

[Scott Danforth]

Given my lack of experience I don't have any idea of a ballpark dollar figure that I am looking at here. I don't mind putting in some sweat equity, but I am trying to do this project the best I can without going broke.

How much to rehab the hull?

How much for a rebuilt long block?

How much for exhaust and all the other stuff that completes a rebuilt long block or that will marinize (?) a used truck motor?

I know there are lots of unknowns...I am just looking for a ball park...

assume $3000+ to rehab the hull. this is new plywood, glue, screws, mixing cups, PPE, tape, buckets, cloth, resin, and foam.

assume $1500-$2500 to redo the interior - this is just vinyl and staples, with a little bit of sewing.

assume your drive will need about $500 worth of love (bellows, u-joint, impeller, seals, etc)

assume some other system on the boat will need about $500 (steering, gauges, lights, etc.)

a junk-yard motor is $300, then add marine intake manifold, new exhaust and migrate over a few electrical bits and brackets from your motor and you have $1500-$1500. A re-man long block will run you about $1500 over the cost of a good core (many machine shops have core motors). a new long block is about $3k

Manifolds and elbows are about $550 a kit. marine intake manifold for a 4.3 4-barrel is about $300,

 

[Scott Danforth]

Here is some light reading on the 4.3 https://forums.iboats.com/forum/eng...history-of-the-4-3-liter-with-casting-numbers

 

[tpenfield]

Here are my guesstimates below, not too far off of the figures mentioned already . . .



> How much to rehab the hull? $3,000

> How much for a rebuilt long block? $2,000 (maybe $1,000 for a good salvage yard block)

> How much for exhaust and all the other stuff that completes a rebuilt long block or that will marinize (?) a used truck motor? $1,000


Hopefully you can use some of the electrical, ignition, and fuel system components from the OMC on the truck block to save a few $$$.

So, figure about $5,000-6,000 to bring the boat back to life.

 

[Travis71]

So I came across a boat on Craigslist (https://easttexas.craigslist.org/boa/6837350664.html) today that has a 3.0L OMC engine in it based on photos. Lots of if's involved, but if the motor is truly good what is the feasibility of moving all the components from the donor boat into my boat?

Would the 3.0L provide enough power since my boat currently has 4.3L?

 

[Scott Danforth]

So I came across a boat on Craigsl
Would the 3.0L provide enough power since my boat currently has 4.3L?

No, it would be a dog

 

[tpenfield]

A half dead dog at that . . .

 

[Travis71]

Thanks gentlemen, that is what I needed to know.

 

[Lou C]

before moving forward...do you have any shops who can work on OMC Cobras, to adjust/repair the shift linkage? This is an important issue. I have taught myself to do what many shops will not do (due to the age of the units, and lack of demand) but if you don't have even one place that will work on these, then if you restore the boat, think about selling off all the OMC stuff and replacing with Mercruiser.

 

[Travis71]

Lou C I was told that there is a local shop that still works on OMC stuff. But I also found some info online (maybe this forum?) about how to properly set up these systems in order to shift very easily. Maybe I am fooling myself, but I am hopeful that I will be able to get it to work.

That being said, I am open to the idea if I can make that switch without too much extra cash outlay. Are mercruiser parts more affordable given that they are still in production?

Am I correct in thinking that the engine block is the same, its just the exhaust and all the outdrive parts are different?

I guess I don't know enough about all that would go into switching over that it seems easier right now to replace what needs replacing on what I have right now.

 

[Bondo]

Am I correct in thinking that the engine block is the same, its just the exhaust and all the outdrive parts are different?

Ayuh,...... Only the Long Blocks are the same,.....

Everything bolted on after is different,.....

The only economical way to do the swap is to buy a rotten donor boat with the driveline ya want, 'n junk the boat for it's driveline,.....
Then bolt it all into the hull yer gonna run,.....

 

[Scott Danforth]

Galaxie22 , to clarify Bondo's comment above, Block, heads, flywheel, balancer, rotating assembly and circulating pump are the only thing that is the same.

all the brackets, the starter, the distributor, the intake manifold and carburetor, the exhaust manifolds, etc. are marinizer specific along with the controls, transom shield and drive.

Bondo is correct, best way to convert is find a crashed damaged hull (something a tree fell on the bow) and buy it complete for the controls, engine, drive, wiring, gauges, trim pump, exhaust, etc.

 

[Travis71]

Pulled the outdrive yesterday. Looks like it hasn't been opened up in quite some time, no surprise there.

When I got the engine running the other day the prop seemed to spin just fine. Now that it's off is there a way to check to see the condition of the drive?


Should the u-joints be all rusty like that?

I'm pretty sure that black plastic blob is what's left of the impeller from the water pump. I assume that if that melted like that while running that could be catastrophic to the engine.


Here's what it looks like on the boat end. It was pretty stuck on there, took some gentle prying to get it all loose and apart.

 

[tpenfield]

looks like a horror show.

You know the u-joints should not look like that and it seems that the gimbal bearing came out with the drive shaft.

It's all uphill from here . . .

 

[Bondo]

I'm pretty sure that black plastic blob is what's left of the impeller from the water pump.

Naw,.... The impeller is inside the drive,.....

I'm guessin' that's what's left of the exhaust shutters,.....

 

[Scott Danforth]

your gimble bearing is toast, the U-joints are probably toast, you will need to pull the U-joint shaft and replace the input shaft seal at a minimum (rusty shafts will eat up the seal).

 

[alldodge]

Ya know, since the gimbal bearing came out with the drive, the housing may have some tolerance issues

 

[Travis71]

I am having problems getting the bearing to come off of the shaft. I have soaked it in WD40. I have heated it with a propane torch, and have gotten semi-aggressive with a hammer and wonder bar trying to drive it off.

Any suggestions?

 

[Scott Danforth]

Cut off wheel.

Then again, any pitting on the shaft and you will be replacing it

 

[Travis71]

Cut off wheel.

Then again, any pitting on the shaft and you will be replacing it

I thought about that strategy and worried about the potential for damaging the shaft. Now that I know the replacement cost there would be some serious anxiety as I tried to execute that approach.