33'x14' Midjet with pitting?

[Sobie2]

So I am looking at this large Midjet Pilothouse with twin KAD42s and 290Duoprop drives. I have found some extensive pitting along the chine up to the waterline. It was a harbor vessel. It is a 1993ish vintage boat. But the plating has got to be 1/2" bottom and 3/16" sides. So is pitting the kiss of death (maybe its superficial)? Regularly steel boats get their hulls re-plated. If the pitting was caused by a hot slip and the boat is now zinc'd and trailered is this ok? The pitting is big enough to see with the naked eye, but the hull doesn't leak.

Run like hell?

Sobie2

[kmorin]

Sobie2, Yes and No.

I'm sorry to have to say this a little light in the info and details department- to evaluate a hull. If you had some pics? could help say thousands of words?

Is pitting limited to the chine up the top sides or is there pitting below the chine from chine to keel? The extent of pitting is hard to give in words but; can you take a pocket knife and gouge some? If its not your hull and they won't let you dig, I'd call for a complete survey.

I'd only agree to a surveyor with at least a dozen past metal boats in his portfolio and at least half them aluminum and I'd want to to have some bank and insurance company references unless this is a famous pillar of the community? I do know some surveyors who unfortunately don't know much about metal and almost nothing about aluminum and are still accepted by the bank and insurance companies. Not trying to be unkind, but don't want you to accept anyone's view if they don't have the experience to reflect on the amount of damage already done. Pitting is damage, and if someone tries to label it -regular corrosion, then run- don't stop just leave.

1/2" bottom plating? That sounds odd to me. If you can find and document the cause of the pitting (??? big issue) THEN you might say that you've eliminated the original cause. Buttttt........
......... the rest of the story is that corrosion cells, once formed, have to be removed in one of several methods or they remain, perhaps dormant but not resolved or 'cured' of the internal action of the metal forming an anodic cell with a cathodic paste of corrosive acidic materials that can be turn on again by wetting.

Hope this helps? answer is with more info we could help more but a reliable marine surveyor needs to put eyes on the hull with HIS pocket knife.

cheers,
Kevin Morin
Kenai, AK

[Sobie2]

Thanks Kevin,

I thought about my post this morning and realized I meant 1/4" bottom not 1/2"

Sobie2

[Sobie2]

Here is the boat. Looking at the spare out drives I gather they must be toast.

It is a cool boat, but the pitting is fairly extensive :(

http://www.alaskaboatbrokers.com/listin ... php?id=247

Sobie2

[kmorin]

Sobie2,
If a broker has the hull listed then it's highly likely a survey is already done? (assumption is my favorite form of "logic"! ) Next, since the boat looks like the asking price is less than half of replacement (assuming a dual I/O, full cabin welded aluminum hull is got to be worth 200k$ plus?) then the hull integrity is fully at question by everyone involved and that means its got to be repaired OR rebuilt OR salvaged; its junk.

Let's say you're still interested? First and foremost is the survey, get a copy of existing (confirm who did the survey and reputation regarding metal boats as this is uber critical to the survey's integrity) to learn if the boat is a total loss? The survey and the surveyor's rep are important because many many... (most) marine surveyors do not fully 'know' metal, especially aluminum. IF you had to pay for a survey of your own, then make sure the surveyor knows aluminum and if not.... get a reputable builder to participate in the survey. Otherwise; run.

Next learn if the pitting is confined to the outer hull area/surface/bottom? If this is true, but close inspection of the bilges and ALL compartments' floors, then; there is a means of repair and restoration. However, if the pitting is inside and outside, then the boat may be a loss as this condition requires much more effort than just Michelangelo welding some pitting sites. This point has underlying facts that could be mentioned but I think you'll find them obvious?

Pitting outside the hull only comes from #1 improper wiring which is very common, unfortunately. #2 it comes from harbor shore power and on board wiring errors, #3 from improper alloys where the builder got a defective or mislabeled alloy material for the hull plates; #4 from parking/slipping/mooring between two crabbers or large steel boats where their on board gen sets and anodic protection used the aluminum boat as the sacrificial anode- (I've only seen this in a couple of welded skiffs tied in contact to larger steel boats.)

However, it the pitting is inside the bilge area and outside then the labor to fill and repair the pits implies dismantling some of the boat in order to get access to cut and weld pitting sites. That is not double the work it would be 10x the implied work. The causes of interior pitting begin to narrow the causes (when combined with the outside pitting) so the original build's integrity becomes more suspect. Run.

Last, (general steps not listing work tasks) can you arrange for or do the overhead bottom repairs implied? If someone tells you the pits can be MIG welded, then you are talking to someone who's knowledge is suspect by making that statement. Then ask that person to give a fixed valued contract (hard money) with liquidated damages for overage of time, failure of QA, and some term of service of the repairs. IF the person makes the statement that MIG will do the work but won't give hard number you have a veracity test of that vendor.

TIG overhead is a pain in the welders' entire body but is the only way I've recovered vessels of this condition. But it should be noted that I use a TIG GUN.... and I do not try to weld overhead with two handed dip rod style TIG. What is implied in the repair is a total bottom cleaning (sand blast or chemical and sanding) then carbide bit excavation of all pits, the TIG floating in the replacement metal, then flat sanding and finally replacing bottom paint- slow, expensive and not easy welding.

So, unless you can meet these criteria listed, I'd say the boat was low priced looking for a sucker to take over a problem built by the uniformed?

Cheers,
Kevin Morin
Kenai, AK

[Chaps]

Sobie,

Is the picture in the ad of the bottom representative of how the entire hull looks? If yes the boat doesn't really look any different than most of the older plate boats that come through my shop. I see a pretty lousy bottom job and the usual assortment of paint blisters and patchy surface corrosion. Do you have any pictures of the deep pitting that concerns you?

I'm in agreement on all counts with Kevin re: pitted boats but all I see in that picture is a boat that needs a good sandblast and a proper paint job.

[ruggit]

If an aluminum plate boat has just minor pitting, can they be handled with just a nice 2 part barrier coat and new bottom paint?

[Chaps]

If an aluminum plate boat has just minor pitting, can they be handled with just a nice 2 part barrier coat and new bottom paint?

If you sandblast first to clean out the pitting (and surrounding metal), then apply a thin anti-corrosive primer like Pettit Alumaprotect, then (optionally) fill the pitting with a fairing type epoxy compound, sand smooth, then apply conventional epoxy barrier coat, then aluminum compatible anti-foul paint. This does not apply to pitting that has morphed into full blown hull cancer. I have sandblasted pitting that won't clean-up at the root, that's a problem that won't be solved by burying it in epoxy.

[ruggit]

Thanks for the explanation. I have no issues, but wondered about the pssibilities.