Mr. Demeanor

Getting ready to convert the boat for salt water use. I have an aluminum intake manifold. How much of a problem will that be? I also have 10 yr old stock manifolds that Im concerned will deteriorate quickly in salt.

cuda

Aluminum intakes and salt water is risky business. You may consider either going with Merlin lined intakes, cast iron intakes, or best yet, a closed cooling system.

Here is a picture of an aluminum intake that failed. The spots have been welded, but the damage was already done.

cuda

This is the end result of the intake failure.

Croozin2

Cuda's right, make sure the aluminum intake you choose is a marine version. The water passages have a bronze insert that cuts down on corrosion significantly. As far as 10 year old exhaust manifolds, you've more than got your money's worth out of them. Trust me, you don't want an exhaust failure on your hands. Been through that and it cost me a new set of heads on one of my engines. The joint between the manifolds and risers on the big block manifolds will leak internally and never show an external leak. The water then sits in the combustion chambers and you either ruin a head over a period of time (or possibly scar a cylinder) or you will hydraulic a motor if enough water gets in. Play it safe and spend a little money - get some new manifolds.

excaleagle42

i run aluminum exhaust and edelbrock air gap intakes (unlined)
in salt water. i lined the water passages in the intake with a stainless steel epoxy paint and flush for about 15 minutes and use "Salt Away" every time with no problems. anodes in the intake water passges wouldn't hurt either.

Mr. Demeanor

I wondered about having the water passages powder coated. Seems like somthing that could be done and solve the problem. I guess I just found an excuse to replace the stock exhuast manifolds. Are the cast hi/perf aluminum exhuast manifolds coated inside to prevent corrosion?

excaleagle42

the manifolds are anodized. the corrosion was very minimal after one season but i believe Salt Away had a lot to do with it.

Scott72

I run in salt water and have looked into all solutions. I contacted "Jet" coating and they said that it wouldn't last on the inside of the intake (at least there coatings). I run a Merlin dual plain aluminum intake without inserts. They only make there single plain manifolds with inserts. I didn't want to run a single plain with my setup. I think Dart may have inserts too off there HP500 manifolds, but once again, single plain. Your only other option is to run Mercs dual plain intake (say off an 454 Mag) which does have inserts (I have one sitting around off a 1989 Mag - looks brand new). I installed a fresh water flush inline with the hose going to the sea pump. Looked at the cheap looking plastic ones, and didn't like them, so we fabricated a bronze one using different parts. I flush for 15 minutes after every run. I pull my thermosat housing (stainless marine housing) every year to check it. Looks good so far (2nd year) but I plan to replace the intake every 3 years to be safe. I also sprayed the inside with zinc primer and a hardcoat paint, but that is coming off in second season. As for manifolds, I had a 1987 Liberator always ran in fresh (stock manifolds) with original manifolds in 1998 (took them off, looked brand new). Two seasons in salt and they were shot (didn't flush that boat though). I run CMI stainless now on my 461.

JON242

My aluminum intake lasted two years in salt water even though I always flushed. I think you're better off with a cast iron manifold.

cuda

I have thought about the zincs myself. I have Merlins on my 302, and there is an extra threaded plug that I could remove and screw in an zinc.