Hi

My friend has an 18ft motor boat fitted with an old (but good) Morris
Vedette engine. I know this is only a 948cc engine, but it does seem
a little underpowered, and only seems to be reaching about 2000 rpm at
full throttle. This is achieved at about one third of the range of the
hand throttle control. If the throttle control is moved any further
than this, the engine note changes slightly (it sounds as though it is
running on choke) but the revs remain the same. When opening up the
throttle in neutral, the engine revs a lot higher (about 3000 rpm?)
and on visual inspection the throttle linkage seems to be opening as
wide as it can go, but I can't understand why it wont reach any more
than 5 knots/2000 rpm or so when in gear and driving the boat along.

I'm thinking it's either a governor fitted to the carb, (although the
higher revs in neutral would seem to contradict this theory) or a prop
problem (the engine has recently been refitted after a rebuild)...

Can anybody shed any light on this, or suggest a way of searching for
faults which may be causing this problem?

Many thanks in advance

MJ