More than 12 HP on my O'Day 30'?

[Ken Cross]

Our Hunter 30 hit 3 knots when I powered it with a 2hp Honda outboard to get her home with a broken prop strut.
I'd begin by figuring out what's wrong with what you have. Ours weighs in just under 10K and we hit about 6.3 WOT with our 16 hp Yanmar. We generally cruise around 5.9 knots at 2,700 RPM.

Ken

 

[thinwater]

I'm betting he was also bucking tide and didn't know it.

 

[FastOlson]

A cautionary note....
When talking about how fast a boat motors or sails, the reference is always speed thru the water.
Info derived from a GPS/chartplotter has a different purpose: SOG and course.
That's why the boat's own KM is so important, especially for questions like the one posed by the OP here.

 

[jviss]

Our 1978 30' O'Day weighs 12,000 lbs

Is this an actual crane weight measurement? I ask because it seems high, and sailboatdata.com lists it as 10,500 lb.

I would look at prop issues, first, and boat bottom, as @FastOlson has recommended.

I would also check to make sure both cylinders are working on the engine. There are folks who ran engines with dead cylinders for years without realizing it.