1998 Bayliner Capri 1952CN Prop Question

[cgvad]

I have a 1998 Bayliner Capri Alpha Gen II prop question. I believe the boat came originally with a 14.25" x 21P prop. It now has a 15.00" x 17P installed by the previous owner and he routinely used the boat at an altitude of 5600 ft. and I am using the boat at an altitude of 650 ft. Ran the boat for the 1st time this past weekend and I was running 30mph @ 2200 rpm WOT. The nominal tach range is supposed to be 4400 - 4800 rpm according to the available data. Is this a prop issue or is the tach inaccurate ? I don't understand what is going on, but the boat performed really well with good acceleration and quick up on plane. Thanx........

 

[Maclin]

If that 30mph at 2200rpm was at WOT then something is not reading correctly.

What engine do you have? What is the recent history, motor swap or outdrive swap?

Jusr a guess, but you should need a higher pitched prop now, just sayin',,,

 

[cgvad]

It has a 3.0L Mercruiser inline 4, rated @ 135hp and I believe it is all original except for the prop but I'm not 100% sure. If the engine or outdrive were swapped I don't know about it. Would higher pitch be returning to 21" or no ?

 

[Stingray185GXi]

Yes, a higher pitch would be returning to a 21 pitch or maybe compromising with a 19 pitch. Increasing pitch is like a taller gear in a car, that is a higher pitch will result in lower RPM at a given speed, better efficiency, and higher top speed at the expense of acceleration. In general you want a prop that will allow your engine to reach the recommend WOT RPM without over revving. If the previous owner used the boat at a high elevation it is likely that you would have to increase pitch to prevent the engine from over revving if you are using the boat close to sea level. I suspect that your tachometer is not working properly, you should address this issue before you make any decision about changing props.

 

[steelespike]

Typically a 17" would be used for water sports with a boat load of people, or severe elevation.
Your tach is whacky. There is a selector switch on the back sometimes operating the switch a few times to clean the contacts may help.
Be sure it is set for a 4 cylinder.Was 30 mph at wide open throttle?
Don't do a new prop till you have solved the tach issue. Tell us about your typical boating activity we can help you select a prop.

 

[Maclin]

A 3,0 in that size boat would be in the 17p range per my guesstimate, so yes, you have a wacky tach. Like steelespike mentioned, it might just be set for the wrong number of cylinders. If it is set for a V8 then the tach will read 50% of what it should, if for a V6 then 66%, etc.

 

[cgvad]

Alright.... all good info. 30.4mph was WOT on GPS. Thanks, didn't know about the tach selector switch. Typically 2 adult POB for all day fishing, calm to 2ft chop. Probably another 120 pounds of gear, 65 lbs of water and about 240lbs of fuel I think. Probably rarely pull a tube. Okay, thanks everyone and I will get the tach corrected 1st and then see what you guys think after that.

It will take awhile to get the tach corrected.... the boat is stored at the lake about 4.5 hrs away. Probably spend the 4th over there and take a look at it then.