Power Problems with a Bayliner 2558 flybridge ( Help )

Joined
Jan 26, 2013
Messages
9
Morning Campers,

The problem is with a Bayliner Cierra 2585 and its been a long battle getting this far!
I have had her rewired over the last 12 months to get the instruments both top and bottom working as they should do.
She weighs around 3500 lbs (3.5 tons)

Prior to me buying her she had "I believe" a King Cobra petrol engine, this has been exchanged for a GM 6.5 General Motors Diesel engine, naturally aspirated with a casting number ending in 2929 I have spoke to GM in the UK and they confirmed it as a 6.5 but can only give the horsepower to be between 180 -200 due to the many differing uses these engine were used for, I have traced the back through to the guy who had this installed and this engine was from a Humvee?? It is also possible due to the serial numbers stamped on the engine (SAM 565 ) that she was marinized by Samurai who are now out of business.

The stern drive is a Bravo 3 leg with a 20" pitch propeller the gearing is 2:1 ratio determined by turning the engine over manually and counting the propeller turns.

The engine starts and runs clean and when not under load will rev to 3900 rpm.
htttp://www.youtube.com/watch?v=PS52ddxmad8&feature=player_detailpage
The fuel system is a manual standyne pump with manual lift pump, fuel lines have been replaced along with filters ect.

When the she is under load she will only run up to 2500 RPM and maintains 11 knots with the tide, 8 Knots against the tide

She does not sound like she is pushing the limits, at the 2500 RPM or straining.

Now the crux of this enquiry,
a; is she under powered
b; geared wrong
c; under propped

I feel sure that someone out there has had one of these engines fitted in a boat in the past and may have some idea of where to go next to get some better figures, the prop calculator formula for slip ect indicates that the prop is under size?

Just trying to get a balanced view from the guys that have more experience than I do.
Many Thanks for any comments

Steve
 
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