Thanks for the reply chris,

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A lot of if depends on the shape, size and use of the deck, if its going to be subjected to foot traffic, fishing poles, waterski's etc then most decks will be around 3mm minimum to stop penetration through the skin. A 3mm skin with be just over 1350gsm of CSM (about 4kg/m2 & 3 layers of 450gsm), if using carbon then potentially you could get away with less, but 200gsm carbon is about 0.2-0.25thk so you'd need 12-15 layers for 3mm.

I guess no one has any thoughts on if 3 layers of 290g/8.5oz cloth over PVC foam would be strong/rigid enough for the boat deck?

The motor trim works fine. The problem occurs only while drifting/ docked. I thought it might have been from the previous owner replacing the lean post/livewell arrangement with 2 helm seat( I have no idea why he did that?), less stern weight. I was able to talk to another owner of the same boat yesterday (all orignial,still has the original lean post) and he has drainage problems also. He even has more rear weight custom SS transom rigging station and a 4stroke 250hp vs. my 2 stroke 200hp. I even took alot of equipment off the boat( all storage compartments are in the bow), no change.

The boat is a 21ft Palm beach center console, from what I read/spoke to other owners it happens to them too... it is a design flaw. The new motor is about 30-40lbs lighter so it just amplified the problem especially when the fuel isn't full. The boat runs/planes fine.  Water collects at the base of steps to the bow/near the helm. I don't want to weight the stern down due to the low transom height/scupper location.  Other than this problem the boat is the best bank for the buck my families owned. It's just a pain to get the slim of the deck after netting bunker.

I'm with Chris; assuming the static trim was correct previously, I would look to redistribute weight to achieve the same angle of trim rather than altering the deck angle.

That said, if changing the engine has corrected or given a better trim angle, then altering the deck angle to account may not be a terrible idea. I would even consider raising the central section of deck and running a channel/drain towards the gunwales depending on the type of boat.

Do you have full trim ability with the motor (assuming it is an outboard) from tucked under to full tilt? What is the boat?

How much lighter is the engine?

Hello, I have a project that I would like some input/suggestions. I have a boat that the deck doesn't drain properly(the new motor is lighter). The deck is solid, so I was thinking of possibly laying pvc foam over the current deck and taperring it so it drains and cover with 3 layers of fiberglass? Do you think 3 layers of 8.5oz cloth(I'm in the US, so aprox. 290g cloth) will be good...too thin...or overkill? It is a center console, so I would have marine plywood laminated under the helm seats to mount/support. All suggestions welcomed.