Prop Pitch???

[WeCatchEm]

Alright so I finally bought a boat last season and here are the specs

1996 Grady White 247 Strike
2006 Yamaha 250hp 4-stroke
Prop pitch=15

Ended up hittin 6200rpm full throttle hitting about 33 knots
5000rpm was 22 knots
The acceleration of this boat was ridiculous and I know I need a higher pitch prop. I could care less for how fast it is starting off, all I care about is a nice cruising speed for trips to Stellwagen burning less gas.

What pitch would you guys suggest for such a setup. I was personally thinkin bout 19 or even up to 21.

Also who's a reputable person/company I can talk to and get some info.

Thanx in Advance

-Tom

[Fin Addiction]

Seems like it is proped correctly if it is reaching its rpm range at WOT. The number that is kinda confusing is 22 knots at 5k...You are burning some serious fuel if you cruise at 5k....I have a 300hp 4 stroke on similar actually deeper V and heavier boat than the grady and my wot is 6100 and I cruise at 22knts at 4200 rpm....I know this means nothing but I wonder if your prop is beginning to slip on the hub or some other oddity....
The 15 pitch doesnt sound right....more like diameter....I would imagine the correct pitch on an engine like that on your boat would be somewhere in the 19-22 degree range....

[Dauntless]

A quick check seems to indicate a spec'd WOT range of 5000-6000 rom for the F250, so to keep well into the upper 1/2 of that range an increase of 1 to 3 inches of pitch (at around 200 rpm per inch P) should lower that now excessive attainable WOT to very approx. WOT of 6000 to 5600 RPM.
Personally , I would not increase pitch more than 1-2", assuming diameter remains unchanged. But... if... the diameter is a bit small now, you may want to increase that 1" ( to reduce WOT RPM approx. 100) and pitch just 1" ( minus another 200 rpm for new WOT around 5900) for more satisfying results of improved cruise speed and economy at say 4000 RPM and stil have go power for little RPM reduction plowing through larger seas.

[fmoore]

I agree the 15 pitch does sound really small. I'd look hard at a 4 blade prop if you want optimal cruising capabilities. Slower top end but less fuel burn and faster cruise at a given rpm. For every 1" of pitch you add you'll drop about 200 rpm. Not sure about who's good around here for props but I'd discuss a 4 blade with a reputable shop and/or send them the prop and let them blueprint/work it.

[chumtini]

What Dauntless said. Sounds like the engine is rev'ing too high at WOT. Is the WOT RPM with the engine trimmed? Is it a yami stainless prop (eg. "15-M" stamped on the hub)? I doubt the hub is spun given the head poppin hole shot you described

Like you said, the best route sounds like a yami shop/dealer that has a few different props you can try before shelling out 500 clams. Your going to need to find a local yami shop you like/trust anyways. Congrats on the new boat!

Question: Does a 4-blade prop improve efficiency? Are we talking clever props?

[shesoffnosheson]

You could try calling Ken at propgods in Florida. He will get you dialed in perfect. You can try different props through him but costs 35 bucks for shipping. He will probably get you there the first time. Worth it imo,your motor`s performance is only as good as your prop`s.

http://www.propgods.com/Content2/Default.aspx

[captnemo]

Seems like it is proped correctly if it is reaching its rpm range at WOT. The number that is kinda confusing is 22 knots at 5k...You are burning some serious fuel if you cruise at 5k....I have a 300hp 4 stroke on similar actually deeper V and heavier boat than the grady and my wot is 6100 and I cruise at 22knts at 4200 rpm....I know this means nothing but I wonder if your prop is beginning to slip on the hub or some other oddity....
The 15 pitch doesnt sound right....more like diameter....I would imagine the correct pitch on an engine like that on your boat would be somewhere in the 19-22 degree range....

pitch in inches not degrees

[LurkerCharters]

17 is the average pitch for most boats that don't have the maximum rated hp engine installed, 19 to 22 would be for a higher performance vessel, defintitely stay towards the top end of their wot spec. overloading an engine with too much prop will burn valves.

[WeCatchEm]

Thank you for the info guys, and yes it is stamped 15m

operating range of motor is 5000rpm-6000rpm
the max hp for my boat is 350hp

Any of you know any reputable places around the south shore mass area for props?

[LurkerCharters]

We get all of our yamaha stuff from 3A Marine in Hingham, John and mel are very knowledgeable, they will get you the right prop. John is a yamaha master tech.