1987 4.3l interchangeability

[w1bcr]

hi all
just got a 1988 searay 18' with a 1987 mercruiser 4.3 175
s/n c333555 casting 10105867
as far as i know this is a non bal shaft/non vortec motor
am looking around for a used truck motor to get on the water
while i rebuild the one in boat as it was full of water and
iol as thick as penut butter
will a 1986/1992 or late fit the 1987 bell housing ?
or should i try and find the same year block ?
thanks jim

 

[Bondo]

will a 1986/1992 or late fit the 1987 bell housing ?

Ayuh,.... The Chevy bellhousin' pattern hasn't changed since 1955,....

A 1 pc. rear main seal motor will bolt up to the flywheel cover, No problem,....

 

[Scott Danforth]

if you stick with non-balance shaft motors, your limited from 1986 - 1992. has to do with how the motor is mounted and the type of mounts.

common DF206 mounts on balanced motors or the squishy ones on the non-balanced

the 4.3 went thru many iterations. 2-piece and one-piece crank seal, balance shaft, or non balance shaft, flat tappet vs roller lifters, steel front covers, plastic front covers, vortec heads, non vortec heads, adjustable rockers, non-adjustable rockers.

Brief history of 4.3 (going from memory so I may be off on one or two of the changes)
Introduced in 1985 model year as flat tappet, 2-piece rear main seal replacement to 229 (3.8)
1986 - received 2-piece rear main seal
1987 - received center bolt valve covers and roller cams
1992 - received balance shaft (and different harmonic damper)
1996 - received vortec heads
1999 - crank pilot changed
2000 - non-adjustable rockers, plastic timing cover

 

[Rick Stephens]

Nothing wrong with choosing a late model motor - easier to find a quality pull from a truck. There are some bumps in the road. But there are some nice gains in performance.

There is no mechanical fuel pump fitting in the Vortec blocks. So you will be building (plumbing and electrical) an electric fuel pump system.

The toughest part is the harmonic balancer is different (usually serpentine belt, while older stuff is usually v-belt) which means the pulleys are mismatched between the Vortec balancer and your marine water pump, alternator and power steering (v-belts). These are going to have to be adapted, or a different harmonic balancer found. The old non-balance shaft harmonic balancer will not fit the newer Vortec block.

Intake manifolds are different - pre Vortec to Vortec. This can lead to issues figuring out carburetor and choke. You MUST use a marine carburetor.


Other than that, the swap is pure gravy

 

[Boisebiker]

No Title

Can you help me identify this motor vintage? It is a replacement motor due to freezing and I am unsure of its vintage. It was put in a 1999 Stingray that was fitted with the 4.3. Serpentine belt tells me it is newer but I cant identify vintage of exhaust risers.

 

[Scott Danforth]

96-98 bat wing manifolds. Boisebiker as I mentioned in your other post, Just for the manifolds alone I wouldnt buy the boat.

 

[w1bcr]

great thanks for the help
leaning towards finding something pre vortex
to avoid changing all belts and pulleys

 

[Rick Stephens]

If that's a motor you are thinking of getting as a donor/replacement, that's fine if you have better exhaust manifolds off the other motor. or want to purchase new style mani's. The picture is of a Vortec - all good other than mani's, and it is complete with all the accessories on front. I would much rather have a complete Vortec with serpentine belt than an older v-belt setup. All you'd need to do is lose the manifolds and that's a great choice for a donor motor.

 

[Coolharts]

I learned yesterday when buying parts that my 4.3L is a truck engine from a late model 2007 - 2014 Chevy Silverado WT or van. The timing cover is a metal cover and is different than the older 4.3L engines. The oil pan is also different and requires a different gasket. IMO if you are going to use a 4.3L truck engine go with the latest model available, many on car-part.com are available with low mileage from salvage yards for $800. The 4.3L was nearing the end of its production life and installed in lower end truck thus was not as popular engine choice when it finally discontinued.

 

[w1bcr]

OK found a truck with a 1989 4.3 in it in good shape
has the same casting number on it so just need to swap out core plugs
but the fuel pump has a cutout for pump but not drilled for
push rod,without knowing if cam has lobe for pump i am
thinking electric is that way to go
any suggestions on a pump and new oil switch ?
2 bbl carb now but may go 4 bbl later

 

[Rick Stephens]

I used the OEM pump so I could use all the mounting hardware and stainless line going to the carb. You have to wire this in with an oil pressure switch inline to power the pump so that the pump turns off if the engine dies.

Pic below is how I set up my 4.3. You can see the pump. The mounting bracket, stainless line for a Weber carb, brass fittings for the pump, rubber mounting o-rings all came from Mercruiser. Note also the solenoid in lower left. I have power going to an oil pressure switch back by the distributor, then that switches the solenoid to power the pump. We do that so we don't burn out oil pressure switches running pump power through them. There is also a 'T' in the power wire going to the pump that comes from the outer small lug on the starter solenoid - the solenoid down on the starter itself. That lug powers the pump while the starter is cranking to prime the carb before oil pressure comes up.