Marinette Boat Forum

Oxidized Aluminum? Hello over the last few months I have looking for a good 28’ Express. I am an engineer and have worked on and owned many old cars and motorcycles but this will be the first old boat. My question is. I saw two really nice looking boats but they both had an issue that I am not sure what to make of. Inside the boat under the floor at the bottom of the hull (at the v) the undercoating was lifter in many areas. These areas were about the length of my hand and about ½ to ¾ high. I cut one of these lifted sections open and it was filled with a white granular substance that I think was Oxidized aluminum. I am guessing this is real bad but I want to make sure. The boats were very nice other than that. I don’t know how much oxide build-up equals how much missing aluminum. Any help would be greatly appreciated.

Hi I wrote the Oxidation note. I guess I should have said corrosion? If any of you guys have experience with this please let me know. I am really looking forward to getting an express but I don't have experience with aluminum hulls.

Look up and read as much as you can on electrolysis. Most of the time you see it as smaller round spots. I have a 28 express and was able to speak with the person that coated the bottom after being completely striped down so i was very comfortable buying it.

I think the white powdery stuff is common on M's. I had it on my (former) boat, could not figure out where it came from. I did suspect that it resulted from interaction between the tarry stuff (soundproofing) and the hull or disintegration of the coating on the tar. I just vacuumed it up and went on to worrying about other things. Could not see any eroding metal inside or outside.

jralbert wrote:I think the white powdery stuff is common on M's. I had it on my (former) boat, could not figure out where it came from. I did suspect that it resulted from interaction between the tarry stuff (soundproofing) and the hull or disintegration of the coating on the tar. I just vacuumed it up and went on to worrying about other things. Could not see any eroding metal inside or outside.

I gota know what that stuff is before I could feel good about making an offer. There must have been about a cup of it under the undercoating.

jmonday wrote:Look up and read as much as you can on electrolysis. Most of the time you see it as smaller round spots. I have a 28 express and was able to speak with the person that coated the bottom after being completely striped down so i was very comfortable buying it.

I have been reading a lot. The meter is reading .8 The hull looks good from the outside.

I assume you are talking about the Capac meter. Point 8 is below the recommended .9 but not frighteningly so. Often, a bottom cleaning will raise that number. Sometimes, it's down because of dirty or loose contacts on the meter. I've experienced both (and was relieved at the results when the original Capac reading was in the .6 range).
I more than a decade of haunting this board, I do not recall anyone pinpointing the cause of the white powder but others may. Have you considered calling in an expert, a tough no-nonsense surveyor to help you assess the boat?

y wacdlw ,
By all means hire a Marine Surveyor who knows aluminum boats
He will be worth his weight in corrosion/oxidation .
bill

This is why a signature is important, where do you hail from?
salt water or fresh

bill wrote:
y wacdlw ,
By all means hire a Marine Surveyor who knows aluminum boats
He will be worth his weight in corrosion/oxidation .
bill

This is why a signature is important, where do you hail from?
salt water or fresh

I am from Erie, pa. The boat is on lake Erie. I do plan on having a surveyor. If anyone knows a good aluminum guy in the Erie area a name and number would be great. I have looked at eight 28' and two 32' boats. I know the twin engine is quicker and backs up much better but I really love the look and feel of the 28 single. less to go wrong and I have to have everything working real good or it will drive me bonkers. Another question. what should the oil pressure read on a 225 (318 cid) The one I am looking at sits at 40 psi from idle to high rpms. other I have seen sit at about 60 psi?

This is the surveyor I used. I interviewed him in advance and he was familiar with Marinettes.

David A. Monak
Monak Marine Surveying
P.O. Box 547
Huron, Ohio 44839-0547
419-656-4680 -Cell
monakmarine@aol.com

I hear you on single versus twins. Way less to maintain. The reason I went with twins is there is very little deadrise on the aft end of the 28 so she does not have so much bite on the water. I wanted a 28 to keep it simple too. Now, we're thinking we should have a sedan. . .

You have nice boating country up there in Erie.

Good luck.

Joe