330 transom rot

[Mangrum27]

I am new to the site, about to buy a 07' 330 and we live in Miami, FL and have some moisture identified in the transom. We know this is a problem with this boat. Does anyone have any fixes or knowledge on this subject?

Also how does it handle in 3 to 5?
Lastly anyone have cruise #'s and WOT with 300's and Zuke 350's?
Thanks in advance for any advise!

 

[wspitler]

Lots of info on this site. If aluminum bang cap has been replaced at repower like mine could be ok. My 330 gets 1.2 NMPG, maybe 1.3 at best. Twin 300 4.2L Yamahas. Bang plate allowing water intrusion is the weakness. Get a surveyor familiar with the model.

 

[seasick]

'Some moisture' doesn't tell us much. If you had a survey ( and if you didn't you may be making a big mistake),
Were moisture readings taken and recorded or are you suspecting that some spots are wet?
As to 3 to 5 seas, the boat should do fine but can you tolerate 3-5s?

 

[wspitler]

The boat is a tank! Weighs 14500#. May not be “comfortable” at 5-8 but not unsafe!

 

[Mangrum27]

Lots of info on this site. If aluminum bang cap has been replaced at repower like mine could be ok. My 330 gets 1.2 NMPG, maybe 1.3 at best. Twin 300 4.2L Yamahas. Bang plate allowing water intrusion is the weakness. Get a surveyor familiar with the model.

What is you cruise speed and wide open throttle speed with those 300s?

 

[Mangrum27]

I certainly don't look for 3 to 5 but they surely find me. Anyone had to cut out parts of the transom? Whats the process

 

[DennisG01]

Seasick brings up a good point about the moisture. First, there will always be "some" moisture. Was the test done soon after hauling the boat? Where was the moisture? As noted, what does the bang cap look like? Anyone can wield a moisture meter - but that doesn't mean the info they provide is valid. In other words, more/better info is needed to offer a better answer.

FYI, moisture in a transom can be a problem with ANY boat built with an unsealed (glassed) transom.

 

[usmm1234]

How do you know you have moisture? Is this a reading from a moisture meter? Your boat has Greenwood Brand Plywood in the transom. That stuff is pretty much rot proof. The 330’s are not generally prone to transom issues. They tend to have issues with the balsa coring in the hull sides, if they have a problem at all.
I was a certified Surveyor years ago, and every boat I ever surveyed, that was kept in the water, would show moisture on my meter. I had a 33 Bertram that showed moisture across the whole bottom. I blasted the hull. Dried it for 18 months. Put 6 coats of epoxy primer on before the bottom paint. One year later. It showed moisture on my meter.
one really good way to check a transom is to have some one put a lot of weight on the skeg on the outboard while you watch the transom. If it flexes. You probably have an issue. You can also tap on the transom with a plastic hammer. A dull thud, generally means rot. A crisp pop means your fine.

 

[wspitler]

What is you cruise speed and wide open throttle speed with those 300s?

Under average loads 22 to 25 kts at cruise. Remember the boat carries over a ton of fuel, so low on fuel is a totally different boat than full of fuel ice bait people water etc. I don’t know about top end wide-open throttle, but Grady-White has a performance bulletin on their website for the 330 with twin 300s that is quite accurate for average load. Check check it out.

 

[Steiss]

I have a new to me, 2005 330, repowered with 2019 Yamaha 300’s. My most efficient cruise speed is 28mph @ 4400rpms 1.1gph. Top speed is 40-42mph @ 5600rpms . (trimmed up a good bit) We took it out in 3-5’s recently, it was fine, felt very safe. But I will say, we tried going out in 7-8’s at West Palm Beach when we picked it up, scared the heck out of us, turned around when we had an opening and followed a 50’ Hatteras back the to cut. We absolutely are in love with our new express!

 

[Ridge Runner]

How do you know you have moisture? Is this a reading from a moisture meter? Your boat has Greenwood Brand Plywood in the transom. That stuff is pretty much rot proof. The 330’s are not generally prone to transom issues. They tend to have issues with the balsa coring in the hull sides, if they have a problem at all.
I was a certified Surveyor years ago, and every boat I ever surveyed, that was kept in the water, would show moisture on my meter. I had a 33 Bertram that showed moisture across the whole bottom. I blasted the hull. Dried it for 18 months. Put 6 coats of epoxy primer on before the bottom paint. One year later. It showed moisture on my meter.
one really good way to check a transom is to have some one put a lot of weight on the skeg on the outboard while you watch the transom. If it flexes. You probably have an issue. You can also tap on the transom with a plastic hammer. A dull thud, generally means rot. A crisp pop means your fine.

What kind of wood does my 04 282 have in the transom? Are they prone to rot? So far, it passes the tests but I have not put a meter on it.

 

[HMBJack]

You can worry all day and night about moisture in your transom. Doing what Longbay Boy (USMM) above suggests is smart. With the boat out of the water, you can actually stand on the lower unit skeg (one foot on each side) and bounce around a bit and observe the transom. If no flex, then you should be good. But having a Surveyor check it out is also a great idea when buying any boat.

 

[Ekea]

3-5' alone doesn't really mean anything. 3-5 at what period? 3-5 at 15 seconds i will do in my kayak. 3-5' at 3-5 sec and it will be an unpleasant day. the boat should handle it, but no fun

depending on how wet the transom is, the repair may be a full replacement. remove motors, cut the whole transom off, and rebuild it. put motors back on. not sure what that $$.

 

[Chessie246G]

Im getting quotes from 4500-10,000 to replace my transom 24 ft explorer... range depends on materials used. Marine ply at the low end, coosa on the high end.

 

[seasick]

You can worry all day and night about moisture in your transom. Doing what Longbay Boy (USMM) above suggests is smart. With the boat out of the water, you can actually stand on the lower unit skeg (one foot on each side) and bounce around a bit and observe the transom. If no flex, then you should be good. But having a Surveyor check it out is also a great idea when buying any boat.

The problem with that test is that it detects more serious rot or delamination issues and not just early moisture.\ intrusion that could lead to bigger problems. Some moisture is common and not an issue to loose sleep about. Sometime all that needs to be done is rebed a fitting , mounting bolts or a transducer's screws.
There is a night and day difference between transom moisture and transom rot. In general, you can not easily detect many instances of early moisture without a marine moisture meter AND a qualified person to interpret the data. The moisture meters sold in the big box tool departments are not designed for transom testing.
Note that hulls just hauled will often read higher moisture than there is and hulls that sat on the hard for long periods may read very low moisture even though they have issues.
Totally rotten coring as well as frozen coring can read as perfectly OK.
As another poster mentioned, rotten balsa coring on the hull sides above the water line are a known issue with some of the larger hulls. That problem can be a very expensive and complicated situation to fix. Unless the balsa core is rotten away, the only way to check is by a moisture survey.

 

[georgemjr]

That transom is reinforced with a thick aluminum bracket across the top, and angled supports for that bracket running diagonally down to the stringers. You are not likely to get flex (even with the test described above) because of this reinforcement. It has no-rot plywood in it during that year. All that being said, it is a known issue that the aluminum "bang plate" used to seal the top sucks, rots, and if you have removed one (I did) you will see that they did not even seal them correctly (there wasn't enough sealant to make contact and the original bead placed on the aluminum was still just the tiny bead they had put there (it hadn't spread out through contact). If you are in the position to remove the motors it would be worth either having it glassed or at the minimum replacing with the plastic bang plate and sealing well. Grady does offer these parts. As was mentioned, some moisture exists in most transoms but if it is shot, replacement is significant and covered well in this forum if you search for it.

 

[everwhom]

If you haven't already purchased, I'd think a good SAMS surveyor would be able to tap the transom and detect any obvious delamination. If you own it and are still very concerned, perhaps a good marina could drill some sample holes (from the inside?) When you say moisture was identified, can you elaborate? I'm not a big believer in moisture meters, esp on a thick transom.

With regard to MPG, I get 1.1 statute miles per gallon with twin 4.2L F250 Offshores, spinning 15" Mercury Mirage Plus props. Best cruise is 29mph (statute) at 4300 RPM. I get pretty much the same cruise regardless of fuel and ice levels, but if I have to drop the tabs for a head sea, that can go down to 1.0 to .9. I do my long run trip planning (i.e. 100 miles to the NE Canyons) assuming 1.0 and planning to have at least 50 gallons when I return to dock.

With regard to seas, I've been out reasonably comfortably in 4-6, but that was with pretty long wave periods of 8 to 10 seconds. I go with the rule of thumb, 1:2 ratio of wave height (in feet) to wave period. So I won't go out if the the period is not at least twice the height (i.e. if it's 3 ft at 5 seconds, I'll stay home, but 6 seconds or longer, I'm fishing)

But yeah, the boat handles the waves very well -- in rougher waters its very sensitive to trim. The tabs force the sharper entry part of the hull into the water and give a deep-V ride, though at the cost of some fuel efficiency.

 

[Chessie246G]

That transom is reinforced with a thick aluminum bracket across the top, and angled supports for that bracket running diagonally down to the stringers. You are not likely to get flex (even with the test described above) because of this reinforcement. It has no-rot plywood in it during that year. All that being said, it is a known issue that the aluminum "bang plate" used to seal the top sucks, rots, and if you have removed one (I did) you will see that they did not even seal them correctly (there wasn't enough sealant to make contact and the original bead placed on the aluminum was still just the tiny bead they had put there (it hadn't spread out through contact). If you are in the position to remove the motors it would be worth either having it glassed or at the minimum replacing with the plastic bang plate and sealing well. Grady does offer these parts. As was mentioned, some moisture exists in most transoms but if it is shot, replacement is significant and covered well in this forum if you search for it.

Im very curious why they use a cap instead of glassing in the top of the transom. The 50$ in materials to fully encapsulate the transom seems like a good idea.

 

[georgemjr]

That is a great question, that Grady has not answered to my satisfaction. They told me they haven't experienced any issues once they changed over from the aluminum bang plate (which corroded) to the plastic one. But, Like I said, mine wasn't sealed properly from the factory. I kept the aluminum one with the tiny bit of sealant as proof not that it is doing anything for me! I guess they figure it works, why change. But with that one improvement, like you said for minimal expense, it is a whole different transom.

 

[moklodge]

Glass doesn't stick to aluminum. The transom coring (Xl Ply) stops an inch or two before the top of the transom. There is then an aluminum L brace capping the wood and then putty sealing the trim cap over the L brace. It's this L brace that bolts into the stringers and gives Gradys their incredible transom strength. Because of this aluminum brace, they cannot glass the top.