Rebuilding or replacing Mercruiser 4.3 in 1996 caravelle 1950SE

[Scottish_joe]

Hi, I think this is quite a specific ask - sorry if it's been answered before, and thanks in advance for any help or comments, no matter how blunt...

I Just bought a 1996 caravelle with Merc' 4.3 and alpha one, with a dud engine but decent drive and good hull.
Seller said it was cranking and did fire then stopped after 10seconds, 2 times, in June this year, not touched it since then.
Drive apprears in pretty good shape.
Engine 0F803207
Drive 0F863885.
Not sure which exact models these are, is the drive an alpha one gen' 2?

I'm in Ohio. I have a lot of boat repair skills including GRP, metalwork, electrics, and some mechanical,

I THINK I have three options, which i'd greatly appreciate any advice on, assuming cracked block:

1) I'd PREFER to rebuild if the parts aren't too expensive, as my labor is cheap and i have the time and some skill, willingness... and would like to do it right.
- is it worth it full stop, to rebuild (assuming i would do a good job) in terms of cost of parts vs final value of that engine in a year?
- is it wise to buy new after market parts (block, gaskets, manifolds etc) other than OEM, to save cash?
- is there any place/company to look for a decent used 4.3 block?

2) Is buying a complete used 4.3 a better option, then sell the parts off the dud?
I am aware that i risk buying a used 4.3 which may have its' own problems... I've seen them for $2500.... is this a sensible cost?
- or do i look for a wrecked boat with a running 4.3 to cannibalise, as it'd be cheaper but riskier....

3) Do i upgrade to a mercruiser 5.0?
- would cost be much different?
- would many parts transfer from the 4.3 to the 5.0, if any?
- is the 5.0 more reliable?



Thanks very much!!!!

-

 

[Scott Danforth]

first, welcome aboard

second. find what is wrong prior to doing anything. as in serious troubleshooting first. you may just need new plugs or fuel in the tank

third, if you need to rebuild - talk to your local machine shop FIRST. the guys that do nothing but build engines.

to swap to a 5.0 from a 4.3, you can use the starter and the drive.

the motors are only as reliable as the nut behind the wheel and the maintenance they receive. both the 4.3 and 5.0 are reliable as hell if maintained.

 

[Lou C]

Just echoing what Scott said, while you'll find a lot of on line sellers of both remanufactured and new 4.3s, a local shop who can build you one might be easier to deal with, especially if they are familiar with marine builds. The 4.3, 5.0 and 5.7 are good, simple durable engines, built properly and maintained properly will last a very long time. If you are going to change from the 4.3 though, why not go up to a 5.7, the 5.0 and 5.7 are the exact same size externally same weight etc. The 5.7 has the larger cyl bore that is also shared with the 4.3. The 5.0/5.7 will require about 4" more space in front of the engine, the length is the only difference from the 4.3. If the 4.3 is a tight fit in your boat you might want to stick with it.

PS if you stick with the 4.3 and it came with the Merc one piece manifolds, do not re-use those, they are known for internal cracking and failures, due to inconsistent core thickness, with your new engine go with a conversion 2 piece exhaust. In fact if the engine will not crank because the cyls are full of water (now rusted no doubt) there's a good chance that the water ingestion was from those manifolds.

 

[Scott Danforth]

Hey @Lou C being a 1996, the bat wings are long gone

@Scottish_joe still need to know what is wrong with the motor before you go any further

 

[tpenfield]

If there is a cracked block, then a long block 4.3 would be a good bet . . . you will probably need to buy new exhaust manifolds (they usually crack first)

Upgrading to a 5.0 would be more involved and $$$

 

[Scott06]

Hi, I think this is quite a specific ask - sorry if it's been answered before, and thanks in advance for any help or comments, no matter how blunt...

I Just bought a 1996 caravelle with Merc' 4.3 and alpha one, with a dud engine but decent drive and good hull.
Seller said it was cranking and did fire then stopped after 10seconds, 2 times, in June this year, not touched it since then.
Drive apprears in pretty good shape.
Engine 0F803207
Drive 0F863885.
Not sure which exact models these are, is the drive an alpha one gen' 2?

I'm in Ohio. I have a lot of boat repair skills including GRP, metalwork, electrics, and some mechanical,

I THINK I have three options, which i'd greatly appreciate any advice on, assuming cracked block:

1) I'd PREFER to rebuild if the parts aren't too expensive, as my labor is cheap and i have the time and some skill, willingness... and would like to do it right.
- is it worth it full stop, to rebuild (assuming i would do a good job) in terms of cost of parts vs final value of that engine in a year?
- is it wise to buy new after market parts (block, gaskets, manifolds etc) other than OEM, to save cash?
- is there any place/company to look for a decent used 4.3 block?

2) Is buying a complete used 4.3 a better option, then sell the parts off the dud?
I am aware that i risk buying a used 4.3 which may have its' own problems... I've seen them for $2500.... is this a sensible cost?
- or do i look for a wrecked boat with a running 4.3 to cannibalise, as it'd be cheaper but riskier....

3) Do i upgrade to a mercruiser 5.0?
- would cost be much different?
- would many parts transfer from the 4.3 to the 5.0, if any?
- is the 5.0 more reliable?



Thanks very much!!!!

-

I did just that in my sea ray 200. Bought it with a known cracked 4.3, but boat only had 37 hrs was in great shape otherwise.
I bought a partial engine plus exhaust manifolds and elbows from a Michigan motors.
A couple of things to consider
my boat was sold with a 5.0 so I had 4” inches in front of the engine in the compartment and the stringers were set up already such that the side motor mounts on the 5.0 that are also 4 ” further forward fit on the same motor mount pad in the stringer So I had to do no fiberglass work.
bothe engines had a serpentine belt drive and electric fuel pump , 96 is a cut overyear so you may a a 96 and up votec or a 95 and older 4.3

I swapped over my wiring harness, starter, flywheeel cover, drive coupler, thermostat housing, even the distributor is the same if you get a v8 trigger wheel cap and rotor, used the same coil, fuel pump, sending units, serpentine belt and accessories. I used a 4 bbl manifold and edlebrock carb so I used the throttle bracket off a merc Webber application for a clean mounting. I did get a 5.0 ignition module used off eBay.
I also got a lot of advice on needing to swap the drive gear ratio. I kept the v6 1.84:1 drive steeped up in pitch from 19” to 21. the drive was so low hours in my application I didn’t want to swap it out.

i just finished my fifth season whole thing works great. knowing what I know now I probably would have just put a 5.7 in, but i thought I would have been too much power. Now I realize it would have been fine but may not have worked with yet a higher pitch prop On the same drive.

I went with a new base engine but at this point Im glad I did because it’s worked flawlessly.
If you don’t have the space in front of the engine just stay with 4.3.
Cheapest route is a 4.3 from a wrecking yard not much work to covert it over to marine .next step up is rebuilding what’s there , depends on what happened to the engine and if you have access to a machine shop.
I had a hard time paying $3 k ish for a used marine bobtail engine. It would have saved a couple thousand vs the partial package I bought ($5 k). I figure I saved $1500 or $2 k by swapping parts over vs buying a reman mercruiser bobtail engine Which at the time was about $7 k.

nit much cost difference between a 4.3 5.0 5.7...all reliable if cared for.

 

[Scottish_joe]

first, welcome aboard

second. find what is wrong prior to doing anything. as in serious troubleshooting first. you may just need new plugs or fuel in the tank

third, if you need to rebuild - talk to your local machine shop FIRST. the guys that do nothing but build engines.

to swap to a 5.0 from a 4.3, you can use the starter and the drive.

the motors are only as reliable as the nut behind the wheel and the maintenance they receive. both the 4.3 and 5.0 are reliable as hell if maintained.

Thanks, and thanks for the quick reply!

Of course, before trashing it I am going to test fuel/spark and work backwards so I can run it or recreate the failure the seller said he had. I have the ability to do that no problem.

The specifics of these engines however and the costs of parts, I am not so clear on.

 

[Scottish_joe]

I did just that in my sea ray 200. Bought it with a known cracked 4.3, but boat only had 37 hrs was in great shape otherwise.
I bought a partial engine plus exhaust manifolds and elbows from a Michigan motors.
A couple of things to consider
my boat was sold with a 5.0 so I had 4” inches in front of the engine in the compartment and the stringers were set up already such that the side motor mounts on the 5.0 that are also 4 ” further forward fit on the same motor mount pad in the stringer So I had to do no fiberglass work.
bothe engines had a serpentine belt drive and electric fuel pump , 96 is a cut overyear so you may a a 96 and up votec or a 95 and older 4.3

I swapped over my wiring harness, starter, flywheeel cover, drive coupler, thermostat housing, even the distributor is the same if you get a v8 trigger wheel cap and rotor, used the same coil, fuel pump, sending units, serpentine belt and accessories. I used a 4 bbl manifold and edlebrock carb so I used the throttle bracket off a merc Webber application for a clean mounting. I did get a 5.0 ignition module used off eBay.
I also got a lot of advice on needing to swap the drive gear ratio. I kept the v6 1.84:1 drive steeped up in pitch from 19” to 21. the drive was so low hours in my application I didn’t want to swap it out.

i just finished my fifth season whole thing works great. knowing what I know now I probably would have just put a 5.7 in, but i thought I would have been too much power. Now I realize it would have been fine but may not have worked with yet a higher pitch prop On the same drive.

I went with a new base engine but at this point Im glad I did because it’s worked flawlessly.
If you don’t have the space in front of the engine just stay with 4.3.
Cheapest route is a 4.3 from a wrecking yard not much work to covert it over to marine .next step up is rebuilding what’s there , depends on what happened to the engine and if you have access to a machine shop.
I had a hard time paying $3 k ish for a used marine bobtail engine. It would have saved a couple thousand vs the partial package I bought ($5 k). I figure I saved $1500 or $2 k by swapping parts over vs buying a reman mercruiser bobtail engine Which at the time was about $7 k.

nit much cost difference between a 4.3 5.0 5.7...all reliable if cared for.

Thanks, great info, appreciate the detailed reply!

I’m not overly worried about top end speed/power,
So a 4.3 might be the easiest. I can move mounts and do Fibreglass work, so if I have the space I guess 5.0 will be more popular when I eventually sell it after I’m done with it...

 

[Scott Danforth]

I would do a 5.7 or 6.2 vs a 5.0. Same amount of work, however the 5.7 and 6.2. The 5.0 doesnt buy much over the 4.3

 

[Scottish_joe]

I would do a 5.7 or 6.2 vs a 5.0. Same amount of work, however the 5.7 and 6.2. The 5.0 doesnt buy much over the 4.3

On the 19ft caravelle? Not sure I need the extra power, or space?

Is cost similar and are parts transferable do you know?

 

[Scottish_joe]

I would do a 5.7 or 6.2 vs a 5.0. Same amount of work, however the 5.7 and 6.2. The 5.0 doesnt buy much over the 4.3

On the 19ft caravelle? Not sure I need the extra power, or have space?

Is cost similar and are parts transferable do you know?

thanks again

 

[Scottish_joe]

Just echoing what Scott said, while you'll find a lot of on line sellers of both remanufactured and new 4.3s, a local shop who can build you one might be easier to deal with, especially if they are familiar with marine builds. The 4.3, 5.0 and 5.7 are good, simple durable engines, built properly and maintained properly will last a very long time. If you are going to change from the 4.3 though, why not go up to a 5.7, the 5.0 and 5.7 are the exact same size externally same weight etc. The 5.7 has the larger cyl bore that is also shared with the 4.3. The 5.0/5.7 will require about 4" more space in front of the engine, the length is the only difference from the 4.3. If the 4.3 is a tight fit in your boat you might want to stick with it.

PS if you stick with the 4.3 and it came with the Merc one piece manifolds, do not re-use those, they are known for internal cracking and failures, due to inconsistent core thickness, with your new engine go with a conversion 2 piece exhaust. In fact if the engine will not crank because the cyls are full of water (now rusted no doubt) there's a good chance that the water ingestion was from those manifolds.

I’ll definitely use a machine shop for testing and machining, plus advice.

But if I go new block and keep the 4.3 I’ll be doing almost everything myself unless totally impossible without serious/specific tools and machines.
I’ll have to buy some kit/tools but I’ll save that cash in paying other people. If I f’up, I’ll have to hope it’s a cheap f’up...

If 5.7 is the same fit as the 5.0, I guess I’d choose between 4.3 and 5.7, I’d assumed it was bigger and heavier.

Engine still hand cranks so I think block is more likely, but I would change manifolds anyway as they’re not in brilliant shape, as you suggest they might be those one-piece ones. I’ll fire some ATF in the cylinders for now.

 

[Scottish_joe]

Hey @Lou C being a 1996, the bat wings are long gone

@Scottish_joe still need to know what is wrong with the motor before you go any further

Yes, I’m heading out this weekend to check:
fuel supply to carb, Fuel pump pressure, carb working ok and run with new fuel off a portable tank

plus

spark at plugs, new plugs if required
Compression

I’ll change oil prior to this and replace fuel filter too.

 

[Scott Danforth]

5.0 is heavier than a 5.7. By about 20#

Both are about 150# heavier than a 4.3

Dont assume anything until you do troubleshooting

And DO NOT turn a motor over by the crank bolt

You either have room for a SBC V8, or you do not. 5.0, 5.7, 6.2 and 7.0 SBCs are all exact same dimensions externally. Big blocks are bigger yet

 

[Scottish_joe]

If there is a cracked block, then a long block 4.3 would be a good bet . . . you will probably need to buy new exhaust manifolds (they usually crack first)

Upgrading to a 5.0 would be more involved and $$$

Thanks. If block is cracked and I go long block plus manifolds, I am assuming the rest of the engine will swap over ok, if I buy the right block? Any company in particular to look to get a block from?
I’ll replace anything that doesn’t look reliable, eg hoses and wiring as required - is there anything you’d upgrade at the same time or do differently?

 

[Scottish_joe]

5.0 is heavier than a 5.7. By about 20#

Both are about 150# heavier than a 4.3

Dont assume anything until you do troubleshooting

And DO NOT turn a motor over by the crank bolt

You either have room for a SBC V8, or you do not. 5.0, 5.7, 6.2 and 7.0 SBCs are all exact same dimensions externally. Big blocks are bigger yet

Great, thanks for the sizing info.
Thanks for tip on crank bolt - I’ll avoid that, but can you tell me specifically why? Just that I’ve seen engine guys over here use a big 3/4” ratchet to turn the crank pulley to rotate and work lube in cylinders prior to firing up an engine laid up for years.

We’ll see when I measure up what fits...

 

[Scott06]

So it doesn’t sound like you know the engine is bad yet? Might just be fuel or carburation ? An engine with a cracked block will run just fine until the crankcase fills with cooling water .
reason not to use the crank bolt is if the engine is locked up you can snap the bolt off Then u are f’ed. Use a strap wrench on the balancer

if it ran for a brief time then conks out and has an electric fuel pump may be he oil pressure switch that supplies power to the fuel pump. Fuel pump, gets power off the starter during cranking , then off the ignition circuit through the oil pressure switch when the key is in run. During cranking could be filling the carb bowl with a little fuel , but then when the ignition is on power is cut off if oil pressure switch is bad.

 

[Scott Danforth]

GM motors will strip the crank threads trying to turn them over by the bolt. Then you throw the crank away

Use a crank socket

If a mechanic turns a motor over by the crank bolt, go elsewhere and get a different (real) mechanic

 

[Scottish_joe]

So it doesn’t sound like you know the engine is bad yet? Might just be fuel or carburation ? An engine with a cracked block will run just fine until the crankcase fills with cooling water .
reason not to use the crank bolt is if the engine is locked up you can snap the bolt off Then u are f’ed. Use a strap wrench on the balancer

if it ran for a brief time then conks out and has an electric fuel pump may be he oil pressure switch that supplies power to the fuel pump. Fuel pump, gets power off the starter during cranking , then off the ignition circuit through the oil pressure switch when the key is in run. During cranking could be filling the carb bowl with a little fuel , but then when the ignition is on power is cut off if oil pressure switch is bad.

Appreciate the bolt tip, I am not one to force things and break them, but I’ll use the strap wrench. Thanks for fault finding tips too, I’ll try them all to be sure before I pull the engine out, but I’m doing my research early on strong evidence.

I myself haven’t confirmed a cracked block through testing, but the seller said it was and apparently a mechanic confirmed this to him. I tend to believe him as the drive is good and newly serviced (new gimbal bearing and all bellows) and the hull is pretty good/title is legitimate, yet he came down to $450... There is water in the oil which I’ve seen today, lends weight to their diagnosis.

 

[Scottish_joe]

Hi, I think this is quite a specific ask - sorry if it's been answered before, and thanks in advance for any help or comments, no matter how blunt...

I Just bought a 1996 caravelle with Merc' 4.3 and alpha one, with a dud engine but decent drive and good hull.
Seller said it was cranking and did fire then stopped after 10seconds, 2 times, in June this year, not touched it since then.
Drive apprears in pretty good shape.
Engine 0F803207
Drive 0F863885.
Not sure which exact models these are, is the drive an alpha one gen' 2?

I'm in Ohio. I have a lot of boat repair skills including GRP, metalwork, electrics, and some mechanical,

I THINK I have three options, which i'd greatly appreciate any advice on, assuming cracked block:

1) I'd PREFER to rebuild if the parts aren't too expensive, as my labor is cheap and i have the time and some skill, willingness... and would like to do it right.
- is it worth it full stop, to rebuild (assuming i would do a good job) in terms of cost of parts vs final value of that engine in a year?
- is it wise to buy new after market parts (block, gaskets, manifolds etc) other than OEM, to save cash?
- is there any place/company to look for a decent used 4.3 block?

2) Is buying a complete used 4.3 a better option, then sell the parts off the dud?
I am aware that i risk buying a used 4.3 which may have its' own problems... I've seen them for $2500.... is this a sensible cost?
- or do i look for a wrecked boat with a running 4.3 to cannibalise, as it'd be cheaper but riskier....

3) Do i upgrade to a mercruiser 5.0?
- would cost be much different?
- would many parts transfer from the 4.3 to the 5.0, if any?
- is the 5.0 more reliable?



Thanks very much!!!!

-

Really appreciate all the comments and help so far!!!