Prop Recommendation For Better Hole Shot - 2012 Bayliner 215 with Mercruiser 4.3

[RudyD]

New boat, top rpms is 3,000 wide open, speed about 30 mph. Takes a long time to get there, will never pull a skier out. Has a 3 blade prop, not sure of diameter or pitch (I'm a novice - sorry, we've all been there at one point). I've heard a 4 blade would help, but not sure if right or what pitch/diameter works. Can't find stock blade props and not sure I have stock on now (bought used). So hoping someone might be familiar with the situation would could recommend a type, size and pitch to try. Thanks.

 

[Scott Danforth]

Welcome aboard

If you are only turning 3000 RPMs, you have a serious issue

You are either down 2 cylinders, have a worn out motor, the exhaust shutters are damaged and plugging the y-pipe, you have crap for fuel or you are seriously over-propped

Go thru the sticky DIY link on low WOT and perform all the recommended testing before you use yhe boat again

 

[QBhoy]

Yeah. Serious issues there...unless someone has put a ridiculously wrong prop on it.
You’re missing about 1800rpm.

 

[jimmbo]

Check what pitch the current prop is, what the gear ratio of the outdrive is(located on the upper gear housing on the trim).
Check the compression of the engine, that all cylinders are getting a good spark.

There is another possibility, the motor was pooched so the previous owner found a 4.3 auto/truck engine and put it in. That rarely works satisfactorily as the torque curve is all wrong for a boat.

 

[TunaFish389]

Which if an auto was put in a cam change would fix.

 

[jimmbo]

If it the used engine was complete, there would be other parts that need changing. But a cam with a Marine Profile would be a start.

 

[briangcc]

Before all the doom and gloom sets in can you get us some more information about what exactly you do have?

On the prop, there's a series of numbers stamped into it. What are those? Spin it to make sure that the number you're giving us is the only number on it. If there are multiples, provide ALL of them.

Next, on your Alpha One outdrive there is a serial number sticker that includes information such as the serial number and drive ratio. What are those?

Next, having experienced this first hand, are you sure the Tach is accurate? I once had one flip out all over the place until you tapped it then it would read correctly.

What's the overall condition of the boat? Has it been sitting in water, rarely used, where there could be an excess of marine growth severely crippling your top speed?

Get back to us with that info and that should be a good starting point.

 

[RudyD]

Thanks for the note and response. I generally don't start with doom and gloom, so I appreciate the sentiment. I'll check the things mentioned in this post. I learned this was in a rental fleet and that perhaps a speed governor was installed. Another thing to check.

The prop is 14 inch 3 blade, 21 pitch. We are running at altitude of 7k feet, perhaps another factor.

 

[WesNewell]

7K feet is a huge factor. There's about 3% loss of hp for every 1K ft above seas level, so you're losing about 50hp of power at 7K ft. So you need to lower prop pitch considerably..

 

[RudyD]

Thanks for the input about altitude. We've ordered a 4 blade 17 pitch. I'll give that a try and report back. Thanks to everyone, great group here! Everyone tried to help and no one acted like a douche and scolded me for being a novice. Hardly seems like the internet at all.

 

[Texasmark]

Interesting having learned of the altitude where boat is operated....like dirty hulls. We just take things for granted if not stated and if we were standing next to the poster and his boat, these things would be obvious.

 

[WesNewell]

I'm just guessing but I think a 17" is still going to be too much pitch in a 4 blade. I started to recommend a 15 pitch 4 blade but that would have been just a guess. I think wot rpm range is up to ~4800 on that engine and I don't think a 17" 4 blade will get you anywhere near that. But it should get you close to 4000.