Some Prop Coaching Needed

[Bergertime]

Hello Prop Experts..  

I was hoping for a little insight and guidance.  I have a 245 Osprey with a carbed 1998 Johnson 225.  When I purchased the vessel from the PO he had a 15x17 alum prop which is on the boat now.  I have not done an official set of performance tests but at WO the boat does abt 5200 - 5300 rpm depending on trim pushing her approx 35 mph on smooth water.  I did not purchase the boat for speed but as fuel costs rise I am wondering if I could get better cruise performance by changing my prop and save some money on the long trips offshore.  I am aware that this motor, although reliable, is not known for sipping gas :)  

I usually run/cruise her at about 4200 - 4300 rpm which gets me approx. 28-29 mph on smooth water when I am running out or cruising across the bay.  It's worthy to note that she jumps up on plane quickly loaded with guys and gear so I am very happy from that perspective.  Now for the ?s....

1) With the boat came a Viper SS 14 3/4x19 in great shape which is collecting dust in my garage.  If I were to switch props what would I expect from a performance perspective with the SS one and would it be worth the effort.

2) Would there be a better option out there that would likely give me better cruise performance (lower GPH) without sacrificing my hole shot.

I am a total novice at this stuff so any thoughts would greatly be appreciated...

PS - I dont have a fuel flow gauge so I don't have the benefit of that insight currently.

Thanks in advance for any suggestions,

Bruce

[fitz73222]

Hey Bergertime,

You are running kind of low on full throttle rpm's so the 19 pitch will only drop the rpm's further at full throttle so the 19 is not going to help. The lower the pitch the higher the rpm's.
Bruce (wing time) has your set up so he will chime in and make so recommendations.

First and foremost is set up the boat with your normal load to establish your typical running situation. Do a compression test on the engine to make sure the engine is healthy. Next, is the boat bottom clean? Does it have bottom paint on it causing increased friction?

With the prop you are running, you should be seeing at least 5500-5600 which would be ideal for a 17 pitch on that boat. Lets see what other 245 owners have to say about your set up.

[wingtime]

Bruce,
 I have a 245 Explorer which is the same hull as your Osprey with the same carbed 225 motor. I think my walk around might weigh a tad more than your boat.  I have a 15 x 17 omc stainless prop on my boat. At wot lightly loaded and on smooth water I turn 5600 rpms at 38 - 40 mph.  I typically cruise at 28-30 mph turning 4200 - 4300 rpms and I burn 14-15 gph.  I'd suggest your first move is to get rid of the aluminum prop (keep it as a spare) and get a stainless.  Your boat is way too heavy for aluminum and I'm certain it is flexing under load.  Fitz is right the 19 is way too much pitch.

Btw my boat has bottom paint on it which costs about three or so mph top end.

[Circle Hooked]

. I'd suggest your first move is to get rid of the aluminum prop (keep it as a spare) and get a stainless. Your boat is way too heavy for aluminum and I'm certain it is flexing under load.

I agree with that 100%, that flex is costing you speed and rpm's.

[flounderpounder225]

Read through this thread, my data is in there also and we have the same boat, go stainless, and call Ken down at prop gods, my 15 x 15 inertia, blew all the competition away, it's a big prop with a lot of rake, works well on our heavy 245's
viewtopic.php?f=13&t=6417&hilit=+Prop

quote="Bergertime"]Hello Prop Experts..  

I was hoping for a little insight and guidance.  I have a 245 Osprey with a carbed 1998 Johnson 225.  When I purchased the vessel from the PO he had a 15x17 alum prop which is on the boat now.  I have not done an official set of performance tests but at WO the boat does abt 5200 - 5300 rpm depending on trim pushing her approx 35 mph on smooth water.  I did not purchase the boat for speed but as fuel costs rise I am wondering if I could get better cruise performance by changing my prop and save some money on the long trips offshore.  I am aware that this motor, although reliable, is not known for sipping gas :)  

I usually run/cruise her at about 4200 - 4300 rpm which gets me approx. 28-29 mph on smooth water when I am running out or cruising across the bay.  It's worthy to note that she jumps up on plane quickly loaded with guys and gear so I am very happy from that perspective.  Now for the ?s....

1) With the boat came a Viper SS 14 3/4x19 in great shape which is collecting dust in my garage.  If I were to switch props what would I expect from a performance perspective with the SS one and would it be worth the effort.

2) Would there be a better option out there that would likely give me better cruise performance (lower GPH) without sacrificing my hole shot.

I am a total novice at this stuff so any thoughts would greatly be appreciated...

PS - I dont have a fuel flow gauge so I don't have the benefit of that insight currently.

Thanks in advance for any suggestions,

Bruce[/quote]

[Bergertime]

Thanks for the insight guys!  It gives me a great frame of reference.  Have a great weekend and stay warm!

Kind Regards,

Bruce

[Bergertime]

One more quick question... What do you think would be a fair asking price for the Viper SS 14 3/4x19?  Its used but in great shape.

-B

[wingtime]

One more quick question... What do you think would be a fair asking price for the Viper SS 14 3/4x19?  Its used but in great shape.

-B

I usually figure half priced for used items and then subtract from there based on condition.  Of course if it is really nice you can ask a bit more...  you can always take less for it if you don't get any bites!