Flinders Island (GBRMP) by boat ???

Martin, best thing to do is contact the charter boat companies, or the tourist information centre in Cairns. That would be my first step.
Cheers.
Tony.

Hallo Martin,
It is good to see posts from other countries, especially Germany here on ExplorOz, I would presume you have done research on Cape York, the best time to travel will be during the Dry Season and best months would be Juli or August, also be aware of Crocodiles in all waters, freshwater rivers and Tidal streams will have Salt Water crocodiles so it is NOT advisable to walk or swim in any streams in Northern Australia, as for the pushbike on the boat I see no reason why not, all I can say is your keen, good luck.
I will be in your Country again next year for Heimspiel 2015 in Juli at Aspach.

.

Two things europeans underestimate about australia are...the distances and the heat....both real chalenges for cyclists.

Riding bicycle to the top of cape york would be an adventure of the highest order and doing it unsuported would be incredibly difficult if not foolish.
Carrying sufficient water alone may make the trip a non starter.

People commonly do the trip on motorcycles...with a substantial support crew and vehicles.

Remember distances of hundreds of Km are common between towns in this country and in areas like cape york..appart from the very few settlements and communities, there are no services and no supplies of any kind.......you can not even rely on there being a source of safe drinking water.

A bicycle may well and truly open up some very economical and very viable traveling options in certain areas...in other areas traveling by bicycle could be considered dangerous in th least.

cheers

Martin
What Bantam says is true, and you have to plan accordingly
But by the looks of it you are indeed doing so, dont be put off totally
Your seaside connections which is the crux of your question would be the easiest part of your trip, and also the easiest for you to resarch directly with companies involved (google =friend). By far the most planning and prep will have to be the CY bike trip. Spares water food shelter, will have to be carried. Backup plans, support, etc,
My teenage son has done similar( outback qld) remote bike trips, but can go max 2 days without support as you simply run out of water. He wanted and started planning a CY trip, which I supported, but that was with vehicle backup that would meet him every two days. (Other things happened so he did not start that trip)
Do not under estimate the trip, but if you plan accordingly it would be interesting.
CJ

@ The Bantam and CSeaJay
thanks for your critical comments.
I have been in Northern Queensland in 2004 and I tried to cycle up from Townsville. Because of the longlasting wet-season in that year I had to change my plans and that's why I left the Cape York Peninsula in Cooktown when cycling via Normanton, Borroloola (Savannah Way), Roper Hwy and Stuart Hwy to Darwin.
Believe me: I know exactly what I'm doing. Since 1984 I'm now cycling and especially in the last 10 years I only prefer remoted places in hot areas where I had to act on one's own.
But it's better you alert unknown people to avoid foolish activities before they will be killed in the unknown wilderness.
CU Martin

I'm just imagining riding a pushbike over those corrugations...

I am impressed by your dedication, but not at all envious!