@UDave69 did you figure out? Ive had this same problem for a while too. I replace the choke solenoid last year and helped for several outings but then it did not. I can hear the click when choke is activated. only happens in water, not at home on muffs
I have been plagued with the same starting issue on my 1987 48hp for last 3 years. I feel like it's a choke or fuel line leak but can't figure it out. I replaced the solenoid, rebuilt carb, had mechanic look at but it can't be replicated out of water.