1998 Bayliner rendezvous 2109 120 force

[Goakley1986]

I’m curious if anyone out there has the same boy and if so what prop you running. We are running a 13.5x14 3 blue aluminum at the moment. It takes forever to plane out, and our top speed is around 20-21mph with about 500lbs of weight on board. If we load it to compacity our top speed is 12-15. I’m wondering if we have the correct prop, or of the 120 is just not enough power. Thanks.

 

[jimmbo]

I will assume the Boat is about 21 ft. if so, 120 hp is plenty of power

I think your motor has issues.
Compression?
Spark 7/16" gap to all cylinders?
Fuel System all clean and Functioning?

Also are the carbs opening Fully when Throttle is at Max?

And how long have you owned this Combo?

 

[Goakley1986]

The motors starts and runs with no problems at all. We bought the boy two years ago. It came from the factory as a combo. The prop however I’m not sure about.

 

[WesNewell]

The 120 hp was the standard engine, however both a 150hp and 175hp were options.The boat weights 3450#. That's a lot of weight for a 120hp engine, but I would agree you either have a lot of extra water weight in the boat or you've got a problem with the engine. Without more info, hard to tell. Just because the motor starts and runs fine doesn't mean it doesn't have low compression or bad fuel, or bunch of other things wrong. It's over 21 years old. When was the last tuneup? What's the wot rpm? Is the hull clean and in good shape?

 

[QBhoy]

I don’t know if that model bayliner to be fair. I know of a 2052 cuddy. What type of style is it ?

 

[Goakley1986]

The hull is clean and in good shape. We always run fresh no ethenol gas in it. Last tune up was about 3 years ago I believe. Wot is 5800-6000. Assuming the gauge is accurate.

 

[WesNewell]

Assuming 5800 rpm with a 14P prop and a 2.07GR, theoretical speed is 37 mph with 0 slip. Getting 21 mph is a 43% slip so something is drastically wrong. Check and make sure your prop isn't slipping or damaged.

 

[jimmbo]

You are getting 20 -21 mph and the engine is at 5800 - 6000 rpm? Either you have a lot of ventilation, and/or a badly slipping hub

 

[Goakley1986]

I’m a little slow on all this. Lol. What causes slipping and how do you fix it? The prop in only a year old and not damaged.

 

[jimmbo]

Slippage is a Measurement of the difference between the Theoretical Distance a Prop would move Forward one revolution vs. what it actually moves Forward, Water is not a Solid so there will be some slippage

Not enough Blade Area, for the HP and Load

From Ventilation
Mounting an Engine too High on the Transom, Having something that causes Prop to be fed Turbulent Water. Poor Prop Design,

Exhaust Gases getting into the blades:
Either by wrong type of Prop, or using a Prop from a smaller Gear Case,
Gap between the Gearcase and Prop allowing gasews to get into blades

Some slippage is needed, just not excessive amounts as it wasted energy. Too Low is also not good.