4.3 rebuild

[Chuckd91]

Ive read alot of the posts here and figured id try it out myself. Ive recently bought a 1994 wellcraft excel 20 cabin boat as a family vessel and its in need of tlc forsure. Ive got soft areas in he floor to address as well as some seat repair. So i figured id yank the engine out and be through with it. Its looking like it may have been exposed to brackish water due to some pretty heavy rust on the external engine surfaces. Since its raw water cooled, i feel its best to open her up and check things out. Its a 4.3 2 barrel sx volvo penta and ive never had the volvo setups apart. Are they similar to mercruiser at all? And what are the differences in the volvo 4.3 and a common gm 4.3? Just figured i would gain some knowledge on the setup before i start gutting it lol.

 

[Bondo]

Ayuh,.... Welcome Aboard,.... Do a compression test,.... No sense in rebuildin' a perfectly good motor,...

 

[Scott Danforth]

Its a 4.3 2 barrel sx volvo penta and ive never had the volvo setups apart. Are they similar to mercruiser at all? And what are the differences in the volvo 4.3 and a common gm 4.3? Just figured i would gain some knowledge on the setup before i start gutting it lol.

first and foremost, all marine 4.3's are GM 4.3's they come from the tonawanda engine plant (just like the truck motors). heads, block, cranks, rods, pistons all the same. however the cam is slightly different.

core plugs on marine motors are brass or stainless, and they run marine head gaskets.

all accessories including the circulation pump are marine specific.

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

 

[Lou C]

Agreed with doing a comp test and leak down if you have the equipment to do so. Pull off the exhaust manifolds and look for rust in the exhaust ports of both the manis and the cyl heads. If you find that you might have to do a valve job and re fresh the heads. Also check for water in the oil. Neglect of an engine used in brackish water will make a lot of work for you. If those manis & elbows are more than 5 seasons old figure on replacing them and the thermostat housing since both are affected by salt water corrosion.

 

[Lou C]

The Volvo SX transom mount is very similar to an OMC Cobra but the drive has cone clutch shifting like a Merc Bravo. Engine mounted impeller like the Bravo

 

[Chuckd91]

The intake manifold and valve covers look rough from the outside. Ill do a conpression check and then pop the manifolds and risers off to take a look inside. Im thinkig if the parts that were exposed to raw water are trashed, i might do a fresh water cool setup. Are any brands better than others in reguards to the fresh water systems? I would imagine that those systems are alot better for the engine in the long run

 

[Lou C]

If it was run in brackish water it's way too late to add closed cooling. There will be flaking rust inside the block and heads and intake manifold. Best time to add closed cooling is when you re-power with a new or reman engine that is not rusted inside. All that rust will repeatedly clog the heat exchanger. You can however, clean out the block cooling passages when the heads and front water pump are off.

 

[Scott Danforth]

The intake manifold and valve covers look rough from the outside. Ill do a conpression check and then pop the manifolds and risers off to take a look inside. Im thinkig if the parts that were exposed to raw water are trashed, i might do a fresh water cool setup. Are any brands better than others in reguards to the fresh water systems? I would imagine that those systems are alot better for the engine in the long run

too late to add fresh water cooling unless you build a brand new motor. personally I would simply run it as it is until the motor is worn out.

 

[Lou C]

Agreed, then if you start over with a new or re-man engine add the closed cooling then.

 

[670hoth]

Common GM 4,3 truck engines from at least early 2000s and up already come with brass freeze plugs and marine head gaskets. Some of them also already have roller rockers for they are essentially the same. There is a lot of discussion that the cam profiles between boat and truck are different but some people that have compared them say that even the cams are the same.

 

[harringtondav]

I'm with Bondo . If it ain't broke, use your restore time elsewhere. My 4.3 has been 100% fresh water, but raw cast iron rusts, as mine is on internal surfaces. If it is so severe to cause a water leak (which I doubt) you'll know it eventually. I'd be more interested in compression, oil consumption, exhaust oil smoke, and any deep knocking. If your 4.3 had regular oil changes, it's probably fit to continue use for a long time. Those GM marine engines are robust.

 

[Chuckd91]

Well the starter was trashed and attempting to replace it was a fail due to extreme rust. After finding water in the oil sump i pulled the engine (after a big fight with the sx outdrive not wanting to be removed) and its rough. I found a water line an inch above the crankshaft behind the flywheel. Its been submerged and stayed that way for a pretty long time. The risers look decent but the right exhaust manifold and head are hard to recognise. Can hardly find the bolt heads. Looks like im going to have to start over and go through it. Not much seems to be worth saving. Got to love a boat. Im debating on doing the build myself or sending a core and getting a complete rotating assembly depending on cost differences vs warranty length. Any suggestions?

 

[Bondo]

The risers look decent but the right exhaust manifold and head are hard to recognise. Can hardly find the bolt heads.

Ayuh,..... Sounds like a saltwater boat,.....

 

[Lou C]

Having 15+ years of experience in salt water boating...
If you want the boat to be reliable and not leave you stranded, start with a decent long block, and a NEW exhaust system. Barr marine makes nice aftermarket OMC/Volvo exhaust systems, I just installed one on my old '88 4.3 last year that originally had the OMC batwings. If you want to keep the boat and make it last, add at least a half closed cooling system. Then keep in mind that you will be changing those exhausts every 5-7 years if you boat in salt water, and if you see rust trails from the manifold/elbow joint area, you should be taking it apart sooner. If you are in freshwater and are just going to re-hab what was probably a salt water boat, then you won't have as much maintenance but will still have to fix everything touched by the salt. Been there and done it.

 

[Chuckd91]

I think it had been in salt more than once forsure. Im only going to be in rivers so it has no salt in its future. I plan to keep this boat and intend on doing it correct the first time. Is there any brand long blocks that are known for quality components? I havent had much luck finding fresh water cooling kits yet, but im pretty sure thats the route ill be going with the new powerplant.

 

[Chuckd91]

Also, what are the main things i can use to identify the year of my block/heads/intake that i have currently? Casting marks like the 5.7 have on the heads?