Welcome to the forum!
We feel you pain in regards to financing. We are in our lower 30's and this has been an issue.
The bank is willing to loan obscene money for a house, but won't budge on boat.
It all boils down to "comparable credit history". This means that you have had a loan before. The issue with this model is if they base the decision on comparable credit history, you can never get a loan. We were told time and time again that if this was pre 2008 this would be a non issue.
The way we got around this was to buy a smaller less expensive boat first, then 2 years later we bought our larger boat. The step in loan helped and putting down a larger down payment made everything work out.
Don't be discouraged, keep working towards your dream!