Anonymous
01-21-2003, 11:19 PM
rejoice
normal member in standard member. 1. 22' cutty cabin, prop size?
I bought a 1989 Shamrock 22' cutty cabin in Noverber, it has a new 351ci Indmar 240/250hp engine. What size prop will give me the best preformance and what RPM range should this engine be operating in.
Date: 12:55 p.m. on 02-09-2001
Capt_Dog
normal member in standard member. 2. Re:22' cutty cabin, prop size?
There are quite a few postings on this subject that you could spend hours reading. The general conclusion is that the stock (factory prop)prop in perfect condition is the best. What is probably more useful is the speed to RPM ratios. They are well documented in postings too. Here is that general conclusion: cruising RPMs should be around 3000 and your speed should be around 20~21 mph. Not much benefit for going slower, but larger penalties for going faster(WOT 28 mph +/-). This is for your hp mind you, there are various hp ratings for your cubic inch measurement (up to 310hp). Also, your temp reading should be around 150~155 at normal 3000 RPM cruise, if fresh water cooled. If it is higher, then get a new impeller now. If it is not FWC then consider doing that now too, especially with a fresh repower. Welcome to the site. Lee
Date: 02:24 p.m. on 02-09-2001
MarkG
normal member in standard member. 3. Re:22' cutty cabin, prop size?
I have a 1991 220 Predator that came w/ the identical engine. The prop was at 14x11 and I had it repropped to 14x10. The main thing is (and the reason I had the prop pitch reduced) that it is propped to give your engine the proper RPM at wide open throttle (usually about 4000-4200 rpm). All the other stuff is secondary. If you want your engine to last, make sure it runs at the proper rpm at WOT.
Date: 02:59 p.m. on 02-09-2001
rejoice
normal member in standard member. 4. Re:Re:22' cutty cabin, prop size?
[quote][b]Capt_Dog (02-09-2001 02:24
Thanks Lee for the info. The boat came with two different props, one 14x14 and one 14x15 I'm not sure which is the original one. About fresh water cooling, I'm not convinced that it's worth the money. My last boat was a 1985 Larson and it had a 230hp Mercruser in it and the motor is still running well with raw water cooling (900 hrs). I spoke to a Mercruser rep at a boat show once and he said Mercruser doesn't even recommend fresh water cooling. According to him the additional cost and additional maintenance for fwc isn't worth it. He said that most engine failure isn't due to rusting blocks but is due internal mechanical failure caused by wear.
Date: 03:02 p.m. on 02-09-2001
rejoice
normal member in standard member. 5. Re:Re:22' cutty cabin, prop size?
Thanks Mark, what speed and rpm do you cruse at with that prop?
Date: 04:05 p.m. on 02-09-2001
MarkG
normal member in standard member. 6. Re:Re:Re:22' cutty cabin, prop size?
I usually cruise at about 3000 rpm/ 20 kts. This depends on load and sea state and I use a FloScan to monitor GPM vs RPM. The most efficient cruising speed seems to be about 3000 rpm though, on average.
Date: 04:41 p.m. on 02-09-2001
rejoice
normal member in standard member. 7. Re:Re:Re:Re:22' cutty cabin, prop size?
Thats good news Mark, I hope I can get those number out of my cutty cabin.
Date: 04:50 p.m. on 02-09-2001
Team No Slack
normal member in standard member. 8. Re:22' cutty cabin, prop size?
22' Stalker, will be the same hull as your CUDDY - This is a 1991, 240 HP Indmar. Currently running a 13.5 x 11 Nibral Michigan 3-blade. 3990 WOT @ 30 knots and 22.5 knots at 3000. Tried the new four blade from Shamrock and it hummed like no tomorrow, too much pitch, lost top end. Props are fickle. If it is a 1:1 tranny, it should have come with something close to a 14x11. If you are in the Hampton Roads area, Jerry at Bay Propeller does all my work. (2) day service.
--------------------------------------------------------------------------------
Bill Pacey
Team No Slack
Date: 11:46 p.m. on 02-12-2001
normal member in standard member. 1. 22' cutty cabin, prop size?
I bought a 1989 Shamrock 22' cutty cabin in Noverber, it has a new 351ci Indmar 240/250hp engine. What size prop will give me the best preformance and what RPM range should this engine be operating in.
Date: 12:55 p.m. on 02-09-2001
Capt_Dog
normal member in standard member. 2. Re:22' cutty cabin, prop size?
There are quite a few postings on this subject that you could spend hours reading. The general conclusion is that the stock (factory prop)prop in perfect condition is the best. What is probably more useful is the speed to RPM ratios. They are well documented in postings too. Here is that general conclusion: cruising RPMs should be around 3000 and your speed should be around 20~21 mph. Not much benefit for going slower, but larger penalties for going faster(WOT 28 mph +/-). This is for your hp mind you, there are various hp ratings for your cubic inch measurement (up to 310hp). Also, your temp reading should be around 150~155 at normal 3000 RPM cruise, if fresh water cooled. If it is higher, then get a new impeller now. If it is not FWC then consider doing that now too, especially with a fresh repower. Welcome to the site. Lee
Date: 02:24 p.m. on 02-09-2001
MarkG
normal member in standard member. 3. Re:22' cutty cabin, prop size?
I have a 1991 220 Predator that came w/ the identical engine. The prop was at 14x11 and I had it repropped to 14x10. The main thing is (and the reason I had the prop pitch reduced) that it is propped to give your engine the proper RPM at wide open throttle (usually about 4000-4200 rpm). All the other stuff is secondary. If you want your engine to last, make sure it runs at the proper rpm at WOT.
Date: 02:59 p.m. on 02-09-2001
rejoice
normal member in standard member. 4. Re:Re:22' cutty cabin, prop size?
[quote][b]Capt_Dog (02-09-2001 02:24
Thanks Lee for the info. The boat came with two different props, one 14x14 and one 14x15 I'm not sure which is the original one. About fresh water cooling, I'm not convinced that it's worth the money. My last boat was a 1985 Larson and it had a 230hp Mercruser in it and the motor is still running well with raw water cooling (900 hrs). I spoke to a Mercruser rep at a boat show once and he said Mercruser doesn't even recommend fresh water cooling. According to him the additional cost and additional maintenance for fwc isn't worth it. He said that most engine failure isn't due to rusting blocks but is due internal mechanical failure caused by wear.
Date: 03:02 p.m. on 02-09-2001
rejoice
normal member in standard member. 5. Re:Re:22' cutty cabin, prop size?
Thanks Mark, what speed and rpm do you cruse at with that prop?
Date: 04:05 p.m. on 02-09-2001
MarkG
normal member in standard member. 6. Re:Re:Re:22' cutty cabin, prop size?
I usually cruise at about 3000 rpm/ 20 kts. This depends on load and sea state and I use a FloScan to monitor GPM vs RPM. The most efficient cruising speed seems to be about 3000 rpm though, on average.
Date: 04:41 p.m. on 02-09-2001
rejoice
normal member in standard member. 7. Re:Re:Re:Re:22' cutty cabin, prop size?
Thats good news Mark, I hope I can get those number out of my cutty cabin.
Date: 04:50 p.m. on 02-09-2001
Team No Slack
normal member in standard member. 8. Re:22' cutty cabin, prop size?
22' Stalker, will be the same hull as your CUDDY - This is a 1991, 240 HP Indmar. Currently running a 13.5 x 11 Nibral Michigan 3-blade. 3990 WOT @ 30 knots and 22.5 knots at 3000. Tried the new four blade from Shamrock and it hummed like no tomorrow, too much pitch, lost top end. Props are fickle. If it is a 1:1 tranny, it should have come with something close to a 14x11. If you are in the Hampton Roads area, Jerry at Bay Propeller does all my work. (2) day service.
--------------------------------------------------------------------------------
Bill Pacey
Team No Slack
Date: 11:46 p.m. on 02-12-2001