Prop question
- Thread starter walterv
- Start date
My props just came back. I didn't see the actual report yet but I understand that my port was overpitched and my starboard was under pitched. Makes sense since I was burning more fuel on my port side and unable to reach the same WOT RPM. If this is corrected, I will be an advocate for periodic prop tuning.
My props just came back. I didn't see the actual report yet but I understand that my port was overpitched and my starboard was under pitched. Makes sense since I was burning more fuel on my port side and unable to reach the same WOT RPM. If this is corrected, I will be an advocate for periodic prop tuning.
"Makes sense since I was burning more fuel on my port side and unable to reach the same WOT RPM. If this is corrected, I will be an advocate for periodic prop tuning."
This is a good reason to get the props checked and/or corrected as a result of a noted performance issue. The fact that they could not reach the same rated WOT rpm usually means that one is overpropped a bit as the lagging one is usually under the recommended rpm. It is also another reason I never understood synching engines to a specific rpm as that goal only achieves that each engine is at the same rpm and nothing else.
I hope this works out for you and helps a bunch.
This is a good reason to get the props checked and/or corrected as a result of a noted performance issue. The fact that they could not reach the same rated WOT rpm usually means that one is overpropped a bit as the lagging one is usually under the recommended rpm. It is also another reason I never understood synching engines to a specific rpm as that goal only achieves that each engine is at the same rpm and nothing else.
I hope this works out for you and helps a bunch.
"It is also another reason I never understood synching engines to a specific rpm as that goal only achieves that each engine is at the same rpm and nothing else."
Smitty- Don't you find the exhaust resonance and related vibration cycling of out of sync engines to be rather annoying and pretty exhausting by the end of a trip? I absolutely love my Sturdy Corps' Accusync system that is constantly matching engines from moment to moment as loads change in seas. But as noted above, I do have the props scanned each winter, and serviced to match when indicated.
Smitty- Don't you find the exhaust resonance and related vibration cycling of out of sync engines to be rather annoying and pretty exhausting by the end of a trip? I absolutely love my Sturdy Corps' Accusync system that is constantly matching engines from moment to moment as loads change in seas. But as noted above, I do have the props scanned each winter, and serviced to match when indicated.
"Smitty- Don't you find the exhaust resonance and related vibration cycling of out of sync engines to be rather annoying and pretty exhausting by the end of a trip? I absolutely love my Sturdy Corps' Accusync system that is constantly matching engines from moment to moment as loads change in seas. But as noted above, I do have the props scanned each winter, and serviced to match when indicated."
Hello Sandy - I do not hear very much at all as the exhaust noise is quite low when I am running. You are not that far away so maybe you can try it out some day and see how quiet it is at either station.
I am actually very interested in what you had posted about the props and am curious about it:
- You scan the props each year , have you seen any changes? Made any corrections?
- How close do you feel the ISO 1 levels actually get you? How many chords are measured? Can you post the scans?
- If you get the engines to exactly match the rpms how can the load be matched?
My preference is to match the engine loads with fuel flow meters(I don't have these)or boost gages and watch the performance with the pyros. I guess a good way to match the loads on gas engined boats is with fuel flow or maybe vacuum gages.
Hope this helps
Hello Sandy - I do not hear very much at all as the exhaust noise is quite low when I am running. You are not that far away so maybe you can try it out some day and see how quiet it is at either station.
I am actually very interested in what you had posted about the props and am curious about it:
- You scan the props each year , have you seen any changes? Made any corrections?
- How close do you feel the ISO 1 levels actually get you? How many chords are measured? Can you post the scans?
- If you get the engines to exactly match the rpms how can the load be matched?
My preference is to match the engine loads with fuel flow meters(I don't have these)or boost gages and watch the performance with the pyros. I guess a good way to match the loads on gas engined boats is with fuel flow or maybe vacuum gages.
Hope this helps
I used a company called American Propeller , owner Mark. He saw the props and actually told me they looked good and did not in his opinion need to be serviced this year. Maybe next year he said. Mentioned a bunch of stuff he saw that looked okay. I had him pull them anyway (wanted a baseline) and recondition them. I think he may have thought I am crazy for doing such, but I did get back clean props 
IMHO, as mentioned, needed a baseline and I loved his honesty.
Rob,
Let Joe know, it was 600.00 complete.
Walter
IMHO, as mentioned, needed a baseline and I loved his honesty. Rob,
Let Joe know, it was 600.00 complete.
Walter
Walter , I hope you will feel the following has some relvance to your question and not that your thread is being hijacked.
ATTN CHARLIE! This is a public service potential brain-paralysis warning. Close this thread and run for the hills or another topic for ~10 minutes!!
Smitty, I have mine PropScanned (free, with printout) each year because I run at least 200+ hrs a year and know I inevitably have prop strikes whether I am aware of them or not because I go through a lot of weed windrows miles long that retain a lot of unseen debris , plus locally in Vineyard Sound there are minefields of pots with bouys just subsurface at full current . Offshore frankly there is a lot of hidden cr*p out there. I use Nibral props that hold up well to minor strikes, but eventually the props pay their toll to some degree.
I'd guess on average one or both props scanned have indications they could use re-tuning to ISO Class 1 about every 2-3 years but they may need it several consecutive years depending on happenstance. And I run most of the time from the marlin tower that lets me see and avoid most of the stuff I would not see at the lower station.
... Most... of the time I'm not aware of the props' physical degradation either from vibration or fuel use. And I do have 2 analog dash fuel gauges , 2 mechanical top of tank gauges, 2 FlowScan 9000's with calibrated resettable totalizers and finally a B&G Net Engine System which, amongst other ECM data, supplies very accurate fuel flow and calibrated gal/used totalizers for both engines using the engine's ECM fuel flow algorithm. You could say I'm reasonably covered for fuel data, ...not to mention maintaining pretty meticulous if nearly illegible fueling and hours/nm run data kept up in the logbook. .
These are gassers , so unlike your diesels I have no pyrometer gauges or other related electronic "load" data display like most recent electronically-controlled oil burners have.
Unless I have managed a rock prop-strike (amazingly only once with one prop so far in 26+ yrs with this boat) I generally don't notice out of spec unmatched prop condition as I usually match them back up as soon as I see they are even a little out of ISO 1 . There are so many things that affect fuel usage it's hard to pin any discrepancy on prop condition .
That said , at each full fill-up a fill of say 50-75 gal in each of the 2 tanks is nearly always even within a gallon or 2 with everything normally tuned up well on the MPI engines.
I think for the vast majority of recreational boaters ISO class 1 is far the most cost-value service spec to request. If you have large $30-50K 5 or 6 blade Veems or Acme or higher-end props on an extremely thirsty power yacht, class S or 0 might well make sense but most of us would not notice the difference. Plus, if your prop meets ISO 1 (high accuracy to any given desired pitch spec) , it ...could... by coincidence really also meet class S ( very high ) or even 0 ( extremely high accuracy. ) The requested class just has a % + or - differential range from the exact desired pitch specifications . Higher accuracy = narrower range= higher cost to attain.
That helps individual prop and matched pair load "balance", but it's still important to be aiming for the appropriate target pitch based on your specific engine performance observations to have any servicing be most meaningful in terms of potential performance and economy.
The scans on my 18 1/2 " diameter props are done at 5 "chords"/ radii stations from hub to tip on each blade , with computer recording the action of the run-out sensor device for each blade as the prop is manually turned on an aligned axle shaft. The radii used on mine toward the tips were 50%, 60%, 70%,80% and 90% out but I'm not sure whether 0% is at the prop bore center or the blade root, -probably the former.
I've never posted a pic or document using Photobucket or similar hosting site and would rather not deal with that with limited senior mental tools. If you haven't seen a prop scan I could manage to fax or scan & email a copy .It's mostly bar graphs with added numerical interpretation.
As to your last question, I figure if the props are regularly serviced or at least scanned and confirmed within spec and matched , the engines are looked after by me, the boat is run often and fuel is ValvTect so it is stabilized when fresh and fuel degradation is minimized , trim tabs are used to optimize dynamic NMPG readout at any speed, the Accusync is always used except when maneuvering, and the tank crossover valves are always kept closed, then ... the gas dock fuel pump confirms load was darn near exactly even. .
If the active sync system is not used on this boat , fuel usage differentiation goes way up. Much moreso if the tank crossover valves are left open.
(OK , It's all over now Charlie. Sorry. )
Cheers-
Hello Sandy - Very interesting data.
Using Nibrals I was a bit surprised at the need to have them tuned up often. Although I am quite a bit older and not too comfortable with computers myself I would be happy to scan and post the prop scans on both props for us to see what you are describing.
I am guessing that you have 4 blade props and wondering which transmissions you are using - the make model and ratios may have an affect on props tuning (ie Hurth 360's at 1.68 ratio.)
I have had a number of 4 blade Nibrals scanned and a number re-pitched over the years but I just have not yet seen a situation where there was a change without a significant strike with a prop. Over the years with the same props being used and checked a few times lead me to the conclusion that these props hold up very well. I am sure that a great method to watch the gas engines load is the fuel gages which are not very common in our area on gas engine boats but you already have them. They also give you a quick and easy method to know if one engine (the slave) is having a problem compared to the other engine which most gas boats do not.
My last boat had both fuel gages and well as pyro ad boost gages and that demonstrated to me that the fuel use and load is tied more or less directly to the boost pressure when engines are running in decent tune.
When we run over larger rollers now at an angle off the bow you can watch the boost gages take turns going up and down 1psi or so as the governors react and the engines load side to side in the swell. A boost pressure difference at planing speeds of about 1 psi is equal to about 35 rpms in this current boat.
I had one big prop strike in near the Statue or Liberty about 10 years back and the results were very easy to detect due to the heavy nature of the strike.
Could you tell us what amount of changes were needed and made to the props without a heavy hit?
Why would the props then be out of spec yet the engines performance not detect that?
Are they 3 blade props? What transmissions, types, and ratios?
Why would the fuel use delta on the boat go way up if the accusync is not used?
My email is rkrupka(at)optonline(dot)net if you can send the prop scans I can scan them myself on Monday and post them back here - may take a day till I remember how but eventually I will figure it out.
Interesting data for sure and different form what I have seen with mostly diesels.
Using Nibrals I was a bit surprised at the need to have them tuned up often. Although I am quite a bit older and not too comfortable with computers myself I would be happy to scan and post the prop scans on both props for us to see what you are describing.
I am guessing that you have 4 blade props and wondering which transmissions you are using - the make model and ratios may have an affect on props tuning (ie Hurth 360's at 1.68 ratio.)
I have had a number of 4 blade Nibrals scanned and a number re-pitched over the years but I just have not yet seen a situation where there was a change without a significant strike with a prop. Over the years with the same props being used and checked a few times lead me to the conclusion that these props hold up very well. I am sure that a great method to watch the gas engines load is the fuel gages which are not very common in our area on gas engine boats but you already have them. They also give you a quick and easy method to know if one engine (the slave) is having a problem compared to the other engine which most gas boats do not.
My last boat had both fuel gages and well as pyro ad boost gages and that demonstrated to me that the fuel use and load is tied more or less directly to the boost pressure when engines are running in decent tune.
When we run over larger rollers now at an angle off the bow you can watch the boost gages take turns going up and down 1psi or so as the governors react and the engines load side to side in the swell. A boost pressure difference at planing speeds of about 1 psi is equal to about 35 rpms in this current boat.
I had one big prop strike in near the Statue or Liberty about 10 years back and the results were very easy to detect due to the heavy nature of the strike.
Could you tell us what amount of changes were needed and made to the props without a heavy hit?
Why would the props then be out of spec yet the engines performance not detect that?
Are they 3 blade props? What transmissions, types, and ratios?
Why would the fuel use delta on the boat go way up if the accusync is not used?
My email is rkrupka(at)optonline(dot)net if you can send the prop scans I can scan them myself on Monday and post them back here - may take a day till I remember how but eventually I will figure it out.
Interesting data for sure and different form what I have seen with mostly diesels.
Smitty - My main set of props (out of 3 sets ready to go- the other 2 are bronze) are 3 blade NIBRAL 17D x ~~18.5P x 1.25 bore with slight cup.
Transmissions are VD straight 72C's with 1.88:1 reduction gears( that ratio has reverse-output from eng. rot. ) driven by RH/LH blue 330 hp 5.7L MPI's in a mere 27' express sportfisher w/ m.tower, & likely displacing ~~10k lbs loaded.
I just turned on the computer for the 1st time today and saw the request so I will attempt to scan some propscan info with a brand new "printer" and see if I can coax it to file on my laptop and attach to 1 or more emails to you . If that works you can sort what if anything you might care to post. (sent)
Edit ,adding a few answers:
Re: frequency of scans . No one "needs" to have their props scanned each year as I do. As you suggest it's a good idea if performance/economy declines and if a strike was noted.
For me it's strictly personal preference so I know just what is going on with the props at the end of the boating season after likely multiple flotsam strikes with unknown effect during the year. When I get out, much of the return is quite often after dark and through pot minefields in strong current and radar doesn't pick up barely submerged buoys or boards in weedlines. Stuff happens at any speed.
When I hit the rock with the port prop a couple years ago that was most assuredly immediately & thereafter detectable until the next set of props was swapped in the next day.
But no question on mine likely smaller than your props , just a little out of matched spec has at times been undetectable. Most folks probably would not bother with re-tuning, but since I am right there while the scan is being performed, I usually will opt to leave a prop for tuning even if a blade is at the low edge of the class 1 spec pitch range. Most years both props are adequately near the median class range and I leave with un-serviced props & free preliminary scan printouts for the archives .
The fuel delta would noticeably increase on my boat if the active sync system was kept Off because their is no effective friction control for the throttle controls. In any seas there is annoying throttle creep so I would either be out of sync often or would constantly be manually chasing sync.with the levers. Plus as you mention as the 2 props experience varying loads with roll ,etc. the Accusync matches rpms faster than I can and seems to work much better over time than allowing them to load average by themselves. I really like the active sync - so much better than before I had it added very long ago. But I've been in some others' boats whose engines and controls seem to do that job much better than mine to maintain sync without an active system. ("YMMV") .
I have no intention of trying to tell anyone else what they should do about their props,... just giving a little explanation of what works for me and a little of the why.
I will say however, I doubt I would scan every year if I did not hand deliver and discuss with the same very good prop tech/ shop owner who scans while I am there and is quite willing to answer any questions about my props and general prop theory. That is a huge plus in my book.
Transmissions are VD straight 72C's with 1.88:1 reduction gears( that ratio has reverse-output from eng. rot. ) driven by RH/LH blue 330 hp 5.7L MPI's in a mere 27' express sportfisher w/ m.tower, & likely displacing ~~10k lbs loaded.
I just turned on the computer for the 1st time today and saw the request so I will attempt to scan some propscan info with a brand new "printer" and see if I can coax it to file on my laptop and attach to 1 or more emails to you . If that works you can sort what if anything you might care to post. (sent)
Edit ,adding a few answers:
Re: frequency of scans . No one "needs" to have their props scanned each year as I do. As you suggest it's a good idea if performance/economy declines and if a strike was noted.
For me it's strictly personal preference so I know just what is going on with the props at the end of the boating season after likely multiple flotsam strikes with unknown effect during the year. When I get out, much of the return is quite often after dark and through pot minefields in strong current and radar doesn't pick up barely submerged buoys or boards in weedlines. Stuff happens at any speed.
When I hit the rock with the port prop a couple years ago that was most assuredly immediately & thereafter detectable until the next set of props was swapped in the next day.
But no question on mine likely smaller than your props , just a little out of matched spec has at times been undetectable. Most folks probably would not bother with re-tuning, but since I am right there while the scan is being performed, I usually will opt to leave a prop for tuning even if a blade is at the low edge of the class 1 spec pitch range. Most years both props are adequately near the median class range and I leave with un-serviced props & free preliminary scan printouts for the archives .
The fuel delta would noticeably increase on my boat if the active sync system was kept Off because their is no effective friction control for the throttle controls. In any seas there is annoying throttle creep so I would either be out of sync often or would constantly be manually chasing sync.with the levers. Plus as you mention as the 2 props experience varying loads with roll ,etc. the Accusync matches rpms faster than I can and seems to work much better over time than allowing them to load average by themselves. I really like the active sync - so much better than before I had it added very long ago. But I've been in some others' boats whose engines and controls seem to do that job much better than mine to maintain sync without an active system. ("YMMV") .
I have no intention of trying to tell anyone else what they should do about their props,... just giving a little explanation of what works for me and a little of the why.
I will say however, I doubt I would scan every year if I did not hand deliver and discuss with the same very good prop tech/ shop owner who scans while I am there and is quite willing to answer any questions about my props and general prop theory. That is a huge plus in my book.
I have been a bit shorthanded at work just recently and have not had any time to keep up with these posts.
Sandy was good enough to email me his propscan specs and a generic scan form for posting here. I am sorry I have not been able to really read them or contribute but hopefully I can at least post these here for now....
Hope this helps
Sandy was good enough to email me his propscan specs and a generic scan form for posting here. I am sorry I have not been able to really read them or contribute but hopefully I can at least post these here for now....
Hope this helps
