Lifespan of 4.3 V6?

[Laneman25]

I see a lot of these that are rebuilt, and some with water in the oil. Are these engines reliable long term?

 

[Scott Danforth]

I see a lot of these that are rebuilt, and some with water in the oil. Are these engines reliable long term?

they will outlast the boat, or they will die due to neglect.

with reasonable maintenance, they will last between 4000 hours and 5000 hours.

 

[Lou C]

I’m still running an original 1988 pre Vortec short block on mine. Replaced the cyl heads in 2017, still running well. They will last as long as you maintain the exhaust system & avoid overheating. And this one has been run in salt water for over 20 seasons.
If one of these had water in the oil it’s usually due to bad (un maintained exhaust) or overheat damage (blown head gaskets) that often results in cracked cyl heads. Happened to mine; not a hard or expensive repair though…

 

[Laneman25]

Thank you Scott andLou. How can I maintain the exhaust manifolds, is there a way to see if they are wearing out? I assume the water jackets get thin and eventually rust through?

 

[Lou C]

Yep that’s what happens. It depends on what kind of water you boat in. If in freshwater that can last a very long time. In salt water I plan on inspecting & likely replacing every 5-7 seasons. Doing that I never had a failure from the exhaust in 20 seasons in salt water. What some people find is the elbows have to be replaced but the manifolds in some cases can be reused depending on how good the sealing surfaces look. I leak these them with acetone.
If you see rust stains on the joint between the manifold & elbow it definitely could be leaking inside.

 

[Scott06]

Thank you Scott andLou. How can I maintain the exhaust manifolds, is there a way to see if they are wearing out? I assume the water jackets get thin and eventually rust through?

Are you in salt or fresh water. As Lou points out 5-7 years replacement in salt. In fresh they last the lifetime of the boat generally.

water in oil is from overheat due to people too lazy to replace the impeller then using it hot, or freeze damage. With routine maintenance the rest of the boat will rot if wood structure and the interior will be reached before engine goes.

 

[tank1949]

I see a lot of these that are rebuilt, and some with water in the oil. Are these engines reliable long term?

if salt used maybe 10 years. something will rot or rust out.

 

[Scott Danforth]

Thank you Scott andLou. How can I maintain the exhaust manifolds, is there a way to see if they are wearing out? I assume the water jackets get thin and eventually rust through?

part of the maintenance of a salt water boat is constant raw water pump changes and pulling the elbows and inspecting the manifolds every few years. Additionally, the zincs should be serviced either every 50 hours or every year.

as stated above, a fresh water boat manifolds will last 3-5 decades or more

salt water boat manifolds and elbows will last longer with products like neutra-salt or salt-away run thru the system after each use.

these maintenance guidelines are in the factory service manual for the engine/drive. do not rely on clymer, seloc, haynes or other non-factory service manuals.

 

[Lou C]

The 4.3 is really 3/4s of a 5.7. The main differences are the split journal even fire crankshaft; and the balance shaft on the later models. Neither of these usually causes problems or results in a shorter lifespan. Then on the 4.3 V6 cyl heads you don’t have a pair of exhaust ports right next to each other like the V8 does so the cyl heads on the 4.3 may run a bit cooler than on the V8.
How long they last is all dependent on how you use it & maintenance habits.
Keep in mind that in addition to what’s already been said engine life is dependent on proper propping so that the engine reaches the specified WOT rpm and also that you use high enough octane fuel to avoid pinging and/or detonation. I always used at least 89 in mine. The gas dock I use sells only 93 octane.

 

[Bondo]

Ayuh,.... My '94ish 4.3 is clockin' 'bout 3500 hours plus, still showing 140 / 150 psi compression,......

 

[Lou C]

Even after an overheat blown HGs & water in the oil 6 years after the top end overhaul mines at 160-170. Can’t ask for better than that!

 

[QBhoy]

In my opinion…likely the best all round and pound for pound engine ever put in a boat. Such a success story. Could say the same about the gm engines either side of the 4.3 too. Ain’t no arguing with their half a century of tried and tested record so far. Perhaps more of a testament to them, is that more often than not, they are abused, not cared for well and similar…but still somehow manage to survive their abuse, decade after decade

 

[stresspoint]

my 4.3 is practically Bullitt proof after going through a few let downs.
the original to the boat when i got it had a split block on one cylinder ,
i believe PO also cracked a block due to a leaking exhaust.

block #2 was turned into a franken merk also had a crack that caused me grief because not only was it a cracked block but also a crack in the intake manifold hence why i went to vortec heads and intake but still got water into the oil from hairline cracks that only showed under load ."long story '.

after going through the saga i found a late model / year short motor and went to town ,lots of $ and time spent (shout out to Lou who followed and helped along the way ) to get this motor how i wanted it.
they said you cant make power from these motors but with the right stuff you can , the only let down is that split journals crank does not like high RPM but in shot bursts they are fine..
in hindsight ,best easiest option for me would have been a 5.7 swap " however i am glad i stuck it out getting this little 4.3 to sing because they are solid ( plenty of hours on the motor and its still strong as it was when it went together, .i try to avoid RPMs going over 5500 , as it will hit the 6500 mark very easily and it sounds mean .
55 mph @ 5500 "yea i know" is quite enough for my boat as i cruise @ around 2700 - 3200 and it sips very little fuel.