Engine Help

[Rehi99]

1977 F32 with twin Chrysler 360
First time used since commissioning for the year.
Both engines start and idle fine.
Both engines rev up to about 3800 rpm in neutral.
When underway at WOT both engines throttle back to around 2900 rpm and boat only goes 10 mph.
New fuel filters and gas is good.
Could it be vacuum advance and how to check?
Is there anyone with experience that could recommend new distributors with electronic advance.
Any help would be appreciated.

[oil&water]

1) Was it in the water over winter?

2) Mechanical or electrical fuel pumps?

[prowlersfish]

If left in the water growth is part of the issue . You should be able to check to see if the advance is free ( pull off the cap ) . You should have electronic ignition . IMO the factory electronic is better then aftermarket by far (some will disagree ) .

[Patriciamarie]

I've got same vintage , do they have a common fuel tank obviously the condition is related to both locate the common fault likely fuel restriction , or tank venting , not vac advance , advance is directly related to engine speed not engine load. What other info do you have.