I have the exact same davit installed on my 318. It holds a 10 foot 150lb RIB with a 80lb Yamaha 15hp plus 6 gallons of fuel with no issues what-so-ever. I used it all last year to provide a platform for pulling the kids on a tube without using the 318. Things to note: The outboard can be stored in the fully down position while main boat is in motion. Always pull the plug in the dinghy to prevent rain water from filling it and stressing the davit. The system is extremely strong but I am not sure it would hold an entire dinghy filled with water!
For any U.S. purchasers, the davit system is DUTY FREE the US tariff that states the duty rate is 0% for the product is 8425.19.0000
Just go to the following website:
http://rulings.cbp.gov/ and place the number above in the search field. The tariff will be either of the top two listings.
I picked mine up from the Toronto boat show in 2010 and hauled it back. It fit nicely in the back of a full size SUV.
Sorry the signature pic was from 2009 before Dinghy Caddy.
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2007 Four Winns 318 Vista "Sas Sea Lady"Previous
2002 Four Winns 268 Vista "Girls Knot Buoys"
1999 Sea Pro 235 WA "Bait Me"