The trouble is I don't know..When I had a problem with my engines last year the man from Mercruiser took samples from the fuel and sent it away for analysis. Also, he made several tutting noises as he peered into my Fuel Filter and claimed he could see water on the end of it...I looked...I could see nothing.!... It all turned out ok but has left me V worried!
The whole Fuel thing seems to be a bit of a mystery...I thought if I had my engine serviced regularly I was covered...now it seems more to it!
Question is there something I should be doing before I start the engine to ensure that I am running on good fuel?
as far as i can see, no need for worry. the requirement is that it's used as directed - put fuel in, put correct grade oil in, and have services. That's it. They decide the application, and if it's a special water-flooded submarine design then it'll probly need a waterproof engine box, and if it's a diersel then the fuel at the pontoon will do, and and if it's a boat with open exhausts then they saw that too and if they need superduper baffles they didn't say.
So, both martin's and depsols claims are valid, imho.
Problem is the fuel we all buy is not diesel it is gas oil! a cheaper less refined product than car drivers get at the pumps! I know cos my wife worked for many years in the marketing dept of a well known oil company!
Try using an additive that helps adsorb the water in the fuel and allows it to be burned away harmlessly! you will find these products in most chandlery stores. The fuel is also far more dirty than the one car drivers buy so change the filters regularly because they will block up quickly, particularly if you make sea voyages because this stirs up all the muck at the bottom of your tank and it gets sucked into the filters.