4.3 TKS - Cracked Intake Manifold?

[SCJeep]

Are the 4.3's prone to intake manifold cracking or is it just freeze damage?

I have a friend that just pulled his manifold off of a ~2006ish 4.3 TKS after it died and he found water in the oil. There was no water in the cylinders so we feel like the problem is just the intake manifold. It was cracked along the flat area on the bottom of the intake.

He has drained the block the same way for probably 8+ years, pull the 5 drain plugs from the manifolds and block. It is stored in a non-heated garage and has low hours. So are the manifolds prone to freeze and does he need to pull the hoses off and thermostat housing from now on to drain the manifold? It just seems odd since this was actually a very mild winter for us here in SC.

 

[BillK2632]

I've never heard of a problem with the 4.3 intake manifold. I live in Charlotte NC and my boat is stored in un-heated dry storage - our winters are similar to upstate SC. I fully winterize mine, drain the block/manifolds, fog and fill with anti-freeze. When I pull the thermostat housing, there is still water in the intake manifold water jacket that doesn't drain out. Could be due to the angle the boat is sitting, flat vs on a trailer with the front raised, I don't know. Bottom line, I don't think you are really protected from freeze damage unless you fill with anitfreeze or blow out all the water passages to be certain there is no water trapped anywhere.

 

[scoflaw]

Check your block for cracks as well. Lifter valley area in particular

 

[Lazy Daze]

Agree with everything above. There's no "known issue" - in fact, they have been pretty darn reliable over a few decades of use. Most likely it's just due to the way it was winterized. As Bill mentioned, there's always water that remains in the intake area. Unlike an outboard, that self drains because it's vertically oriented, a stern drive/inboard is mounted horizontally so you have to force the remaining water out. This is actually one of the things that I'm constantly warning people about regarding winterizing - although it's usually more about the "bucket method" (sucking AF in through the drive). The problem is, people see this done on Youtube and it looks so simple. And, of course, because it's on Youtube (or you hear that famous line of "it works fine for me") in MUST be true, right? :smt101

But, to get back on point, nearly every time that I winterize an engine (and I drain it first), I see a good amount of water come out of the intake area as I push AF in through the hoses. So, yes, you're most likely correct in your line of thinking that it was from not getting that water out during winterizing. Why it happened this year and not others? Well, that's the $64,000 question! :smt001

 

[CliffA]

I live in upstate SC also.

Can't help you with the manifold question but can tell you how I winterized my smaller boats when I owned them.

I just drained the engine and exhaust by removing the blue plugs. But I also used the exhaust from a wet/dry vac to blow out the engine and exhaust after the plugs were removed and the water was drained. I did not fill the engine with antifreeze. I don't think our winters are cold enough or long enough to go to that extent but supposedly this helps protect the internal engine passages from corrosion. I personally don't believe this small amount of corrosion protection is worth the cost and effort of using antifreeze in our area. our boats only need to be winterized for 3 - 4 months. its just personal preference to use antifreeze or not.

cliff

 

[SCJeep]

Thanks for all the quick replies. We suspect it was freeze damage and for whatever reason the intake did not drain this year. Live and Learn.
I also took note because I keep my boat stored at home in the garage and really skimp out on winterization. My garage is attached to the house but not heated, and has a bonus room above. My hot water heater (gas) is in the garage so it generates some heat. Last year I didn't even drain the block, I monitored the temps and they never got below 40F. In the past if we were going to have a really cold spell in the teens I would drain the block.

Has anyone upgraded to better intake (performer?) and 4b carb? He's looking into doing this upgrade since he's got to buy a new manifold anyways, just curious if the fuel lines and throttle linkage will all match up.

 

[CliffA]

Has anyone upgraded to better intake (performer?) and 4b carb? He's looking into doing this upgrade since he's got to buy a new manifold anyways, just curious if the fuel lines and throttle linkage will all match up.

IMO and based on some research the amount of hp/torque gain from going to a 4 brrl carb will barely be noticeable and will not be worth the cost in parts and effort and future increased fuel consumption.....

cliff

 

[scoflaw]

Probably could be repaired easily enough. Cheaper than new and everything would bolt back on with no mods.

 

[BillK2632]

Yeah, let's get this thing fixed, we are getting dangerously close to a winterizing discussion here in July!:smt009