1990 Mercruiser 4.3 Same As???

[GulfCoast2572]

I know the Mercruiser engines are GM blocks with some slight changes. So i just want to make sure there is nothing wrong with getting parts from the same model year auto engine. I know the Chevy S10 has a 4.3l option, so can i get parts from a 1990 Chevy S10 and they will work without an issue in a 1990 4.3l Mercruiser?

Thank You in Advance
Mike

 

[Buster53]

What parts are you looking to get? Anything electrical must be a marine version. Pretty sure same goes for the carb. Marine engines also use a different cam.

 

[GulfCoast2572]

What parts are you looking to get? Anything electrical must be a marine version. Pretty sure same goes for the carb. Marine engines also use a different cam.

I am mainly looking for internal parts, I know i need a piston, rod and oil pan and maybe a crank... (We wont talk about why). Also thinking about changing the fuel pump, oil pump etc. If i am going to rebuild the engine might as well.

I do know the cam is different, and it has different freeze plugs and a couple other items.

Thank You!!

 

[alldodge]

Internal parts are the same "IF" you get a truck motor and not a car.

Fuel pump and carb must be marine
Brass or stainless freeze plugs and and marine head gasket (not auto type)

Ignition must be marine except for coil

 

[GulfCoast2572]

Internal parts are the same "IF" you get a truck motor and not a car.

Fuel pump and carb must be marine
Brass or stainless freeze plugs and and marine head gasket (not auto type)

Ignition must be marine except for coil

Awesome Thank You!!!

 

[Lou C]

If you have a mechanical fuel pump this also
Must be a marine unit with the safety overflow hose that goes from the pump to the carb.

 

[Scott06]

Oil pan is likely marine specific too. You may be able to find the GM number for this vs getting a Merc one

As mentioned above fuel, electrical, and exhaust are marine specific.
Long Block wise the only diff between truck & Industrial and Marine is generally marine head gaskets and brass or SS freeze plugs (both wont corrode in raw water cooling), and the cam . Generally the cam is close enough on truck vs marine, do not use an automotive cam need Marine/RV/towing cam.

 

[Chris1956]

Circulating pump is marine, it has brass impeller and SS back plate and bolts. Distributor holds MerCruiser ign components. It may be unique to MerCruiser. Head gaskets and exhaust manifold gaskets may be marine as well.

Are crankshaft bearings 4 bolt?

 

[Scott06]

Are crankshaft bearings 4 bolt?

Not always. Im sure some higher end motors are 4 bolt but plain jane 3.0/4.3/5.0 are not 4 bolt.

 

[stresspoint]

Circulating pump is marine, it has brass impeller and SS back plate and bolts. Distributor holds MerCruiser ign components. It may be unique to MerCruiser. Head gaskets and exhaust manifold gaskets may be marine as well.

Are crankshaft bearings 4 bolt?

i wish ,

 

[Lou C]

Not only are they not 4 bolt mains but there are only 4 main bearings and they had to use the split journal crank to make the 90* V6 an even fire engine. Even so there is still a harmonic vibe at about 1800 rpm that the balance shaft was designed to damp out. That said they are tough engines that can take a beating. I know mine has. Still running the same old 35 year old short block. Got reman cyl heads back in ‘17.
Keep oil in it, don’t overheat it & prop it correctly and they last a long time

 

[Scott Danforth]

If you have to dive into the internals on the 4.3, you don't just replace a single piston

The block needs to be bored and honed and you replace all the pistons

With that stated, look for a complete low mileage 4.3 from a truck.

Strip the motor down to a short block and heads.

Knock out the steel core plugs and install brass

Install marine head gaskets

Install marine circulation pump.

Now put on the marine front accessories, the marine compliant intake, distributor, starter, etc.

Remember the 4.3 went thru many generations.

The 1990 is in the 1988-1991 generation (non balance shaft)

1992-1995 is the next gen with balance shafts.

1996-2000 is the first of the vortec heads

light reading. https://forums.iboats.com/threads/complete-history-of-the-4-3-liter-with-casting-numbers.693935/

 

[stresspoint]

Not only are they not 4 bolt mains but there are only 4 main bearings and they had to use the split journal crank to make the 90* V6 an even fire engine. Even so there is still a harmonic vibe at about 1800 rpm that the balance shaft was designed to damp out. That said they are tough engines that can take a beating. I know mine has. Still running the same old 35 year old short block. Got reman cyl heads back in ‘17.
Keep oil in it, don’t overheat it & prop it correctly and they last a long time

yep , mine is still copping a beating , i just don't let it rev past 5500 rpm.
it will easily go too 6200 rpm but i back off so as i don't break it.