AQ171c's Vapor Lock?

[moresparks]

Hi guys,
Just need confirmation of a problem.
I think I have a vapor locks on my AQ171c’s.
I have had no problem starting normally, you have to follow a routine of a few pumps and then feathering the throttle and all is well.
I took the boat out for a good run yesterday and all was fine no problems. Went to the boat this morning and neither engine would start.
Now it was extremely hot yesterday in fact the hottest day so far in the UK.
I checked the plugs and they looked dry. The Carbs look o/k, fuel pumping from the fuel pump and jets checked and cleaned. Accelerator pump all working o/k. “Both Engines”!! The only thing in common is the fuel and the weather. Now I know I have some old fuel with preservatives and octane boosters etc, in the tank which I have slowly been diluting with fresh. I can try with a temporary fuel tank filled with fresh, but any other tips or possible causes please?
Thank you for your patience.

 

[moresparks]

Well!! After hours of painstaking checking and cleaning I finally managed to get them to start. They are running fine now. I haven’t a clue what caused the problem, seems the issue was possibly around the mixture screws. I have reset these and re-synced the carbs, so only time will tell. I know they were incredibly difficult to start after a run so it doesn’t exactly fill me with confidence should I stop for lunch or do a bit of fishing.

 

[el_pescador]

If that ever happens to you try to start with the throttle somewhere between 3/4 and maximum and be ready to pull back to idle once it starts. Having difficulty starting after a long run is not uncommon on VP 4 cylinder OHC engines.