Low part of rpm range - ok to run there?

[1badhusky]

Belive my 4.3mpi's rpm range is 4400 - 4800 - just put on a new four blade 21 pitch. WOT w/ 3 people on board today and it was just at 4400 rpm.

Would a 1-pitch lower prop be better for my engine?

Thinking w/ more people on board, I wouldn't be able to pull 4400 rpm - so lugging my engine.

Is running in the low range better/worse for feul economy? Any other issues I should know of? Am I missing out on top speed b/c I'm not pulling that extra 400 rpms?

Thanks!

Boat is 2007 bayliner 185 - weighs 2300lbs

 

[steelespike]

Re: Low part of rpm range - ok to run there?

I do think a 19" pitch is better.It will improve your hole shot and allow you to operate within the rpm range easier over a broader load.Just be aware of your rpm
with a light load. When changing props it is best to stay with the same brand to
get more predictable results.As you may know the 4 bld alone will improve your hole shot and allow you to stay on plane at less power with less diddling of the throttle.

 

[1badhusky]

Re: Low part of rpm range - ok to run there?

That's the new plan - going to a 19 - believe dropping 2 inches will add 400 rpm and put me right at max rpm.

Why would bayliner put such a big pitch on there stock - a 3 blad 23???

 

[TilliamWe]

Re: Low part of rpm range - ok to run there?

...

Would a 1-pitch lower prop be better for my engine?

Thinking w/ more people on board, I wouldn't be able to pull 4400 rpm - so lugging my engine.

Is running in the low range better/worse for feul economy? Any other issues I should know of? Am I missing out on top speed b/c I'm not pulling that extra 400 rpms?
...

Yes
You are thinking correctly
Worse, you are creating more of a "load" on the engine
Lugging your engine will lead to valve damage. It only gets uglier from there.
Yes, you are missing out on top speed without those last 400rpms. (You may be missing out on top speed with that "extra" blade too.)

 

[Silvertip]

Re: Low part of rpm range - ok to run there?

And a great big NO to better fuel economy just because the engine runs slower. Fuel economy is determined by throttle opening. Since you are lugging the engine at 4400 rpm that requires more throttle opening than the same speed would require with the engine running freer. The more the throttle is open the less manifold vacuum is available and the more fuel is consumed. An engine can run at 4400 throttled back slightly as well as at 4400 with full throttle because it is being lugged. And if the prop is wrong at that rpm it is wrong across the entire rpm range.

 

[steelespike]

Re: Low part of rpm range - ok to run there?

Generally factory prop selection would be for the most speed.And if lightly loaded may do well enough though hole shot might be a little sluggish.No doubt they listed
other props more suited to a users typical activities.