Anonymous
01-21-2003, 11:10 PM
J.D. SOUTH
normal member in standard member. 1. MORE PROP CONFUSION
I am the new owner of a 1992 200 SE, (center console). The boat has the 302 engine , with a 1:1 velvet drive transmission.I found it late this summer with 296 hours on the clock.
The boat was super clean, and had been kept in very original condition.
As I became acquainted with my new little shammie, I took for granted the slower out of the hole to plane was a trade off to the inboard power.(have owned numerous V-6 outboards over the years).
Then in my normal blundering ignorance I stumbled onto the mechanics corner where the subject of prop sizes seemed to be a fairly hot topic.
My boat had a 13/ 13 prop dated 10/91 so I assume it is the original prop, in reasonably poor condition.
Performance with original prop is terribly slow to plane , 2800 rpm cruising speed 23.5 to 24 mph on the GPS. tOP SPEED IS 34 MPH AT 3600 RPM.( These speeds are not taking into account for upwind ,downwind, crosscurrent , barometric pressure or relative humidity, I am way to simple to try to factor all that into the equation).
After visiting my friend at the Marine Connection, armed with my new 13/12 prop and the you can bring it back in 30 days as long as you dont ding it warranty, I headed out for instant performance improvement.
With the new prop installed out of the hole performance is great, damn near feels like an outboard.Cruising speed at 2800 was an almost ubelievable 29 mph, again on the GPS, seat of the pants certainly verified the GPS, or is that GPS verified seat of the pants performance.
Boat was great outside in a 3 to 4 ft. sea, great throttle response climbing swells etc.
Now for the downside, WOT throttle was 3300 at about 31 mph.Since I dont run the boat wide open , and stay at 2500 to 3000 rpm, should I ignore the fact this engine should run at 3800 to 4200 at WOT?
I understand over propping is hard on the transmission if the engine is laboring but that is not the case, any comments or thoughts would be appreciated.
My new shammie (IMPACT) is everything I had hoped for, love that V-8 grunt.
Date: 09:24 p.m. on 11-06-2000
Leprechaun
normal member in standard member. 2. Re:MORE PROP CONFUSION
JD - Your results appear somewhat contradictory and I'm not sure why. You say you got 3600 rpm with an old beat-up 13X13 prop and now you put on a spanking new 13X12 and get LESS rpms at WOT? Something is not right. Granted, we all pretty much agree that Shamrock slightly over-propped these boats straight out of the factory, but if anything, you should get more rpms out of less pitch. I have to talk to my buddy Screaming Eagle (My dock mate) about his experiences w/props on his 20' Predator, but your speeds and rpms seem high and low respectively with the new wheel. We need more hands-on experience and input from 20' owners. Leprechaun
Date: 07:26 p.m. on 11-07-2000
Capt_Dog
normal member in standard member. 3. Re:MORE PROP CONFUSION
I agree it sounds contradictory. Is the new prop cupped? That would be the only explantion to the less RPM more speed claim. Let us know. Lee
Date: 06:59 a.m. on 11-08-2000
leprachaun
normal member in standard member. 4. Re:MORE PROP CONFUSION
Not all props are created equal. Take your prop to a shop that has propscan technology to find its true pitch. I had a friend with a brand new 28 Albemarle and the engines were off 300 rpm from each other. Propscan revealed one at 17 x 18, the other 17 x 20, although stamped 17 x 19. One inch of pitch should be 200 rpm. Dropping one inch should have increased rpm, not decreased it.
Date: 01:04 a.m. on 12-28-2000
Engineman
5. Re:MORE PROP CONFUSION
Sounds like the shop left out some info such as cup degree and blade area. But the first thing to check is the tachometer. If the engine is in fact only turning 3300 rpm's or so it will not be long until you will have to do some major engine work due to overloading. Sounds as though the tach is off because others report similar speeds with normal rpm's. By the way normal should be about 4000 rpm's at WOT. With out a properly calibrated tach all other prop work will be mute.
Date: 04:15 p.m. on 01-02-2001
J.D. SOUTH
normal member in standard member. 6. Re:MORE PROP CONFUSION
Lep,Dog,& Engineman, thanks for the replies and information . Like my dad use to say, son always check the easy stuff first.
During a routine clean up and inspection of the engine compartment I was checking the routing and action of the throttle and shift cables. After opening the throttle I tried to manually open the secondaries on the carburator. I felt pretty fair resistance to them opening.Further inspection revealed a pretty fair amount of corrosion on the secondary vacuum shaft, which was obviously not allowing the secondaries to open either at all , or at least allthe way.
A quick ICW run later that day brought a good throaty sound to the engine at WOT, and 3850 RPM at I believe 37 MPH on the GPS.
The most embarassing part of this is I guess I sea trialed the boat before I bought it , and didnt realize I was running the boat on a two barrel carb. Boy am I a discriminating knowledgable buyer !
Having crummy winter weather ,for south Florida, soon as I can get outside will give you an update on the local billfish action here on the southeast coast.
Date: 12:30 p.m. on 02-03-2001
Engineman
7. Re:MORE PROP CONFUSION
Engine speed is VERY important. The engine should opperate at 4000-4200 WOT.
First check the tachometer. Make sure what it says is accurate.
Second make sure the carb is opening all the way.
Third check the timing advance, if the springs are old they may not be pulling the plate around.
All this before another prop change might be beneficial.
Date: 01:00 p.m. on 02-06-2001
normal member in standard member. 1. MORE PROP CONFUSION
I am the new owner of a 1992 200 SE, (center console). The boat has the 302 engine , with a 1:1 velvet drive transmission.I found it late this summer with 296 hours on the clock.
The boat was super clean, and had been kept in very original condition.
As I became acquainted with my new little shammie, I took for granted the slower out of the hole to plane was a trade off to the inboard power.(have owned numerous V-6 outboards over the years).
Then in my normal blundering ignorance I stumbled onto the mechanics corner where the subject of prop sizes seemed to be a fairly hot topic.
My boat had a 13/ 13 prop dated 10/91 so I assume it is the original prop, in reasonably poor condition.
Performance with original prop is terribly slow to plane , 2800 rpm cruising speed 23.5 to 24 mph on the GPS. tOP SPEED IS 34 MPH AT 3600 RPM.( These speeds are not taking into account for upwind ,downwind, crosscurrent , barometric pressure or relative humidity, I am way to simple to try to factor all that into the equation).
After visiting my friend at the Marine Connection, armed with my new 13/12 prop and the you can bring it back in 30 days as long as you dont ding it warranty, I headed out for instant performance improvement.
With the new prop installed out of the hole performance is great, damn near feels like an outboard.Cruising speed at 2800 was an almost ubelievable 29 mph, again on the GPS, seat of the pants certainly verified the GPS, or is that GPS verified seat of the pants performance.
Boat was great outside in a 3 to 4 ft. sea, great throttle response climbing swells etc.
Now for the downside, WOT throttle was 3300 at about 31 mph.Since I dont run the boat wide open , and stay at 2500 to 3000 rpm, should I ignore the fact this engine should run at 3800 to 4200 at WOT?
I understand over propping is hard on the transmission if the engine is laboring but that is not the case, any comments or thoughts would be appreciated.
My new shammie (IMPACT) is everything I had hoped for, love that V-8 grunt.
Date: 09:24 p.m. on 11-06-2000
Leprechaun
normal member in standard member. 2. Re:MORE PROP CONFUSION
JD - Your results appear somewhat contradictory and I'm not sure why. You say you got 3600 rpm with an old beat-up 13X13 prop and now you put on a spanking new 13X12 and get LESS rpms at WOT? Something is not right. Granted, we all pretty much agree that Shamrock slightly over-propped these boats straight out of the factory, but if anything, you should get more rpms out of less pitch. I have to talk to my buddy Screaming Eagle (My dock mate) about his experiences w/props on his 20' Predator, but your speeds and rpms seem high and low respectively with the new wheel. We need more hands-on experience and input from 20' owners. Leprechaun
Date: 07:26 p.m. on 11-07-2000
Capt_Dog
normal member in standard member. 3. Re:MORE PROP CONFUSION
I agree it sounds contradictory. Is the new prop cupped? That would be the only explantion to the less RPM more speed claim. Let us know. Lee
Date: 06:59 a.m. on 11-08-2000
leprachaun
normal member in standard member. 4. Re:MORE PROP CONFUSION
Not all props are created equal. Take your prop to a shop that has propscan technology to find its true pitch. I had a friend with a brand new 28 Albemarle and the engines were off 300 rpm from each other. Propscan revealed one at 17 x 18, the other 17 x 20, although stamped 17 x 19. One inch of pitch should be 200 rpm. Dropping one inch should have increased rpm, not decreased it.
Date: 01:04 a.m. on 12-28-2000
Engineman
5. Re:MORE PROP CONFUSION
Sounds like the shop left out some info such as cup degree and blade area. But the first thing to check is the tachometer. If the engine is in fact only turning 3300 rpm's or so it will not be long until you will have to do some major engine work due to overloading. Sounds as though the tach is off because others report similar speeds with normal rpm's. By the way normal should be about 4000 rpm's at WOT. With out a properly calibrated tach all other prop work will be mute.
Date: 04:15 p.m. on 01-02-2001
J.D. SOUTH
normal member in standard member. 6. Re:MORE PROP CONFUSION
Lep,Dog,& Engineman, thanks for the replies and information . Like my dad use to say, son always check the easy stuff first.
During a routine clean up and inspection of the engine compartment I was checking the routing and action of the throttle and shift cables. After opening the throttle I tried to manually open the secondaries on the carburator. I felt pretty fair resistance to them opening.Further inspection revealed a pretty fair amount of corrosion on the secondary vacuum shaft, which was obviously not allowing the secondaries to open either at all , or at least allthe way.
A quick ICW run later that day brought a good throaty sound to the engine at WOT, and 3850 RPM at I believe 37 MPH on the GPS.
The most embarassing part of this is I guess I sea trialed the boat before I bought it , and didnt realize I was running the boat on a two barrel carb. Boy am I a discriminating knowledgable buyer !
Having crummy winter weather ,for south Florida, soon as I can get outside will give you an update on the local billfish action here on the southeast coast.
Date: 12:30 p.m. on 02-03-2001
Engineman
7. Re:MORE PROP CONFUSION
Engine speed is VERY important. The engine should opperate at 4000-4200 WOT.
First check the tachometer. Make sure what it says is accurate.
Second make sure the carb is opening all the way.
Third check the timing advance, if the springs are old they may not be pulling the plate around.
All this before another prop change might be beneficial.
Date: 01:00 p.m. on 02-06-2001