A far better alternative, in every way, is to use silicone hose. Demon Tweeks - www.demon-tweeks.com - are a good source as the hose is often used in motorsport. It can be bought preformed to the correct shape and then cut to length. More expensive than normal butyl hose but cheaper and far better than Yanmar stuff.
When I wanted to replace hoses on the Perkins Marine diesel the mechanic said they were not a stock item so go to an auto parts outlet and go through the rack of hoses to find one with the right diameter and right bend(s). He said I would have to cut out the piece I wanted and bin the remainder.
He said the people who marinised the Perkins would have done that and pointed to a hose which appeared to have been cut to length with a knife.
If I was in your situation I would not want to be ripped off by Yanmar either.