Aluminum exhaust service life?

[brwn234]

How long will a set of aluminum exhaust manifolds and risers last running in fresh water and occasionaly brackish water? I've been looking at Revolution until I found a site that will sell me an EMI set with everything for $1215 to my door. I cant find any warranty info at either website either.

[mjw930]

How long will a set of aluminum exhaust manifolds and risers last running in fresh water and occasionaly brackish water? I've been looking at Revolution until I found a site that will sell me an EMI set with everything for $1215 to my door. I cant find any warranty info at either website either.

Service life should be about the same as cast iron, between 3 to 5 years. If you plan on having the boat for a while consider the SS risers. Those can probably go through 2 replacement manifolds before they need replacing.

[boatnut]

I can give you one data point: we have a '69 18' with H&M aluminum log manifolds --- still functional after 39 years. I used to run in SF bay (salt) occassionaly for the first 20 years or so -- for the last 20 years it has only been used in fresh water. Same block and volvo (aluminum) drive also. Ed

[yeller]

I had a set of Glenwood aluminum log manifolds and risers. Ran the boat in fresh and salt for 18yrs without any sign of corrosion.

[MOP]

I have seen aluminum setups last longer in salt then iron, I am running all aluminum on mine in salt. I do flush very well after each use!

[mjw930]

I have seen aluminum setups last longer in salt then iron, I am running all aluminum on mine in salt. I do flush very well after each use!

I"m hoping that's the case. I have a set of GLM aluminum manifolds and risers to replace the iron ones on the 7.4L now. These come with zinc anodes to help and I always flush with Salt Away. These are an interim system until I pull the motor to rebuild / improve it. If the manifolds last I may simply replace the risers with SS tubes when I do the rebuild.

[blueliner]

I have seen aluminum setups last longer in salt then iron, I am running all aluminum on mine in salt. I do flush very well after each use!
what is the normal amount of flush time required to be on the safe side??? i flush mine each time as well for about 10 minutes... is that overkill or not enough??? thanks or the info

[mjw930]

If you have a thermostat then you need to flush it long enough to get the thermostat to open to get the salt water to flow out of the block.

I use Salt Away and wait until the thermostat opens to start the solution. It takes about 5 minutes to work through all of the mixture and I shut it down just before the solution runs out so the water that remains in the motor has some percentage of the solution in it.

10 minutes from start to finish seems about right.

[f_inscreenname]

I"m hoping that's the case. I have a set of GLM aluminum manifolds and risers to replace the iron ones on the 7.4L now. These come with zinc anodes to help and I always flush with Salt Away.

Do yourself a favor and pull those pencil zincs before they rot and fall off the mount plugs and they cause more issues then they are worth. I was told by many to do this and didn’t until it was to late. Took about a hour shaking and fishing to get mine out and that’s after I took it off the motor.

[mjw930]

Do yourself a favor and pull those pencil zincs before they rot and fall off the mount plugs and they cause more issues then they are worth. I was told by many to do this and didn’t until it was to late. Took about a hour shaking and fishing to get mine out and that’s after I took it off the motor.

I haven't installed them yet. At what interval did you check them before you discovered it broken off?

I searched the entire web for info on GLM and in no search did anyone mention not using the pencil zincs. I would think if this was a chronic issue I would have stumbled across a post of 2 about it. Oh well, glad I found out now.

[f_inscreenname]

I haven't installed them yet. At what interval did you check them before you discovered it broken off?

I searched the entire web for info on GLM and in no search did anyone mention not using the pencil zincs. I would think if this was a chronic issue I would have stumbled across a post of 2 about it. Oh well, glad I found out now.
Check on iboats.
I would say about 6 months. Just to much water passing over them and them being to small/thin. If you feel you have to use them get the shortest, fattest that will fit. I will just flush after use and never have to hear that rattle again.

[mjw930]

Saltaway functions no better than common liquid dishwashing soap..

Do you have proof of this?

I've been using it as a flush since '98 and one one teardown my engine builder was amazed at the difference between my motor (always flushed with salt away) and another with roughly the same hours in the same water that only used a water flush. Perhaps I would have had the same results with dishwashing soap, who knows.

Regardless, I searched for negative comments on the product and couldn't find any. I did, OTOH find a number of seemingly independent tests that have been done to confirm the claims. I guess if they also tested using dishwashing detergent we would know the answer.

http://www.jetskicentre.co.uk/store_parts_saltaway_testresults.htm
http://www.sandiegofishing.com/buddydb/showthread.php?t=20976

[MOP]

what is the normal amount of flush time required to be on the safe side??? i flush mine each time as well for about 10 minutes... is that overkill or not enough??? thanks or the info

About 15 minutes, the manifolds and risers get fresh water before the Tstat opens, I stick my hand in the water coming from the exhaust and taste it for salt.

Phil

[blueliner]

About 15 minutes, the manifolds and risers get fresh water before the Tstat opens, I stick my hand in the water coming from the exhaust and taste it for salt.
Phil

with my 496ho, i am only flushing the heat exchangers, right??? since it is a closed-cooled engine, i am trying to mkae sure there is no salt water in the headers and such... if i am mistaken, please correct me. i flush mine immediately after it is on my lift. thanks

[BUIZILLA]

I believe your doing the HE stack, all hoses for such, and the exh. risers...

[mjw930]

I believe your doing the HE stack, all hoses for such, and the exh. risers...

Exactly, the only major difference is you don't have to worry about the thermostat opening so you can probably get away with a 5 minute flush.

I wouldn't go less than 5 minutes simply because it may take that long to dissolve any residual salt residue that's already began to leach from the sea water.

If you are flushing from the inside with a T in the intake hose then also let the water run with the motor off to backflush the outdrive.

Another option, one that I've used on other boats that can stay in the water for a few days, is to put 2 flush valves in, one on the intake side (at the sea strainer or on the hose leading to the sea water pump) and another in the hose leading from the sea water pump to the motor intake. That way I can flush the motor and risers from the second connection without running the motor while the boat is still in the water.

NOTE: make sure all T's have waterproof caps and one way valves and make sure all connections are double clamped. If one of the caps blows off or a hose comes loose your boat will be going to the bottom just like someone opened up a 1.5" hole in the hull.

[yeller]

...I stick my hand in the water coming from the exhaust and taste it for salt.
PhilAnd I thought I was the only one that did this because the looks I always got. :eek:

[blueliner]

i just raise it on my lift, hook up the muffs and crank her over... seems to work pretty well. i guess all of those other options are great if u don't have the convenience of the lift. thanks for all the input... glad to know 10 min should be ample time
Exactly, the only major difference is you don't have to worry about the thermostat opening so you can probably get away with a 5 minute flush.

.

I wouldn't go less than 5 minutes simply because it may take that long to dissolve any residual salt residue that's already began to leach from the sea water.

If you are flushing from the inside with a T in the intake hose then also let the water run with the motor off to backflush the outdrive.

Another option, one that I've used on other boats that can stay in the water for a few days, is to put 2 flush valves in, one on the intake side (at the sea strainer or on the hose leading to the sea water pump) and another in the hose leading from the sea water pump to the motor intake. That way I can flush the motor and risers from the second connection without running the motor while the boat is still in the water.

NOTE: make sure all T's have waterproof caps and one way valves and make sure all connections are double clamped. If one of the caps blows off or a hose comes loose your boat will be going to the bottom just like someone opened up a 1.5" hole in the hull.

[mjw930]

i just raise it on my lift, hook up the muffs and crank her over... seems to work pretty well. i guess all of those other options are great if u don't have the convenience of the lift. thanks for all the input... glad to know 10 min should be ample time

Let me clarify, on my 22 I use muffs, the other fittings I'm talking about are from past boats I've owned that had separate raw water pickups so muffs weren't an option.

One thing to be aware of, city water supplies or any standard plumbed garden hose cannot supply enough water to run the motor at anything much over idle. Keep it under 1000 RPM or you risk hot spots due to lack of water flow.