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Author Topic:   MONTAUK E-TEC 90

katpil posted 12-06-2014 03:31 PM ET (US)
Late this fall I re-powered my 1990 Montauk with a new E-TEC 90. I am using the old propeller, a SST 13-7/8 x 19, that I had on the prior engine, a 2001 Johnson 90 V4. I ran this propeller for ten years on the old engine and was satisfied with its performance. With the old engine on flat water, WOT, one person onboard, my GPS would show 43-MPH at about 5,300-RPM. On the E-TEC, I'm getting 39-MPH at 5,650 rpm in similar conditions. The E-TEC is mounted fairly high on the transom, two holes showing above the upper mount bolts [which sounds like a two-hole up mounting positing---jimh]. I know that 19-pitch is on the top end for this boat and motor combination. Should I lower the mount position down two holes? Should I be getting a different propeller?
jimh posted 12-06-2014 03:56 PM ET (US)
Your old engine was V4 with more displacement. It may have been more powerful than the three-cylinder in-line new engine.
The recommended full-throttle engine speed range for the E-TEC 90 is found at
http://continuouswave.com/whaler/reference/ETEC_EngineRPM.html
For a recent model E-TEC 90 the optimum range is 5,000 to 5,200-RPM. With your boat and propeller, you are reaching full-throttle speeds that are quite a bit higher than the optimum. My first instinct is to look for a different propeller with a combination of more pitch and perhaps more diameter, so that full-throttle engine speed moves into the recommended range.
The engine mounting height is more a function of the particular propeller. Some propellers tolerate higher mounting better than others. Many modern engines run at two-holes-up position with modern propellers.
Putting your data into my propeller calculator at
http://continuouswave.com/cgi-bin/propcalc.pl
shows a calculated SLIP of 13.7-percent, which is a littler higher than usual. (I used 2.25:1 for the gear ratio. Check your owner's manual to see what the gear ratio is on your engine and let us know. Gear ratio is important in propeller selection.)
Since the present full-throttle engine speed is 5650 and optimum is 5200, the engine can come down about 400-RPM. That is often indicative of increasing pitch about 2-inches. That would be 21-pitch, which seems like a lot of pitch for the boat.
The propeller calculator predicts about 41-MPH for
RPM=5200
RATIO=2.25
PITCH=21
SLIP=10
I am also curious about the diameter of your present 19-pitch propeller. It sounds a little small.
katpil posted 12-06-2014 04:16 PM ET (US)
Thanks Jim, The gear ratio is 2:1. I'm hesitant to go over 19" pitch on this motor, seems most are running 17 or 15 on this setup. I was thinking that perhaps the prop is pulling in some air at WOT since its up two holes, I'm used to the old days when engines were mounted all the way down. This motor only has 2 hrs use on it so I'm not really attuned to its sounds and signals yet. But it didnt sound out of the ordinary to me. I may lower it one hole and see what that does. And, just doubled checked, it is a 13 7/8 dia prop.
jimh posted 12-06-2014 07:29 PM ET (US)
RPM=5650
RATIO=2
PITCH=19
MPH=39
SLIP=23.3-percent--TOO HIGH
The propeller is not really performing well.
http://continuouswave.com/cgi-bin/propcalc.pl

Is that speed really in Statute Miles Per Hour?
katpil posted 12-06-2014 11:36 PM ET (US)
I think I'll lower the engine a hole or two and see what happens. That slip number could mean it getting air and disturbed flow from the hull, IMO.
tedious posted 12-08-2014 02:57 PM ET (US)
Unless you are obviously blowing out (such as in turns) there's no need to lower the motor. You need a taller prop, and a better one. The old SSTs were good for their day, but that was a long time ago. I would try something like a Stiletto Advantage in size 13.24x19. That should bring your RPMs down and also provide less slip / better grip.
Tim
Alan Heckman posted 12-08-2014 03:26 PM ET (US)
If my memory is correct I think Tom Clarks recommended prop for an ETEC 90 is a Stiletto Advantage 13.25 x 15 mounted 2 holes up. Maybe some of you ETEC guys could verify that. That is on a Montauk 17.
katpil posted 12-08-2014 10:36 PM ET (US)
Perhaps another interesting piece of data.....the day of the installation the dealer took me out for a quick shakedown run. With me standing behind the RPS and him at the wheel, WOT rpms were 5350. I didnt have the GPS so I dont have a speed with that. To me that would indicate the prop was getting a better "bite" with the extra weight in the stern. Has prop technology really changed that much that I should ditch the SST and try a Stiletto?
tedious posted 12-09-2014 09:01 AM ET (US)
Yes, a Stiletto will perform better than your old SST. You didn't specify if it's in good condition - with that level of slip, it almost seems like it must be dinged up a bit, reducing the effective pitch. Either way, going with a Stiletto or other newer-tech prop will improve your performance across the board. You paid a lot for a nice new motor - why handicap it with yesterday's technology when it comes to a prop? You can get the Stiletto from Dan's Discount Props for $279, including the required hubkit.
In general, I'd go with Tom Clark's recommendation. I don't think you want to lower the motor or add more weight in the stern unless you're looking to reduce your top speed and burn more gas.
Tim
katpil posted 12-09-2014 01:25 PM ET (US)
Thanks for the info Tim. Actually the SST, although I have used it for 12 years is in perfect condition. Except for a bit of fade in the paint it looks new....
Alan Heckman posted 12-09-2014 01:39 PM ET (US)
Just looked some old posts. An ETEC 90 with a Stiletto Advandage 13.25 x 15 mounted 2 holes up gets 41 mph at 5200 rpm. Some people are also running the ETEC 90 3 holes up with good results.
Alan Heckman posted 12-09-2014 01:45 PM ET (US)
Just to clarify my previous post both these mounting heights were using the Stiletto Advantage 13.25 x 15 stainless steel prop.
tedious posted 12-10-2014 02:02 PM ET (US)
Something's not completely adding up. I'm hard pressed to believe that the cupping on the Stiletto more than makes up for the additional 4" of pitch and 5/8" diameter of the SST. SO in theory, katpil should not be able to turn that prop that fast, and if he was, he'd be seeing more top end.
Something is causing an extreme amount of slip with the SST.
Tim
jimh posted 12-10-2014 10:02 PM ET (US)
I was wondering about the tachometer accuracy, but, since the value is given to 50-RPM, I presume it is a digital readout from NMEA-2000 engine data. That is usually precisely accurate engine speed.
katpil posted 12-10-2014 10:16 PM ET (US)
Agree, something isnt stacking up. I'll be doing some experimenting this spring on flat water. Need to experiment with trim and see if this set up turns correctly, etc. I'm just thinking that with the extra person on board the transom was deeper in the water allowing the SST to get a better "bite".
tedious posted 12-11-2014 08:09 AM ET (US)
Getting more bite is where the modern props like Stiletto excel - I don't know how to describe it, but it just feels like it's gripping the water better in all conditions.
Tim
crabby posted 12-11-2014 10:11 AM ET (US)
You either need a 17 inch pitch SST or the 15 inch pitch Stiletto as recommended above.
My Montauk is a 1985 with a 2004 90hp ETEC swinging the 15 inch Stiletto (after trialing both 17 and 19 inch pitch SST props when I first hung the motor back in 2004).
katpil posted 12-11-2014 07:05 PM ET (US)
Crabby....did you have the same [performance] with the SST props [as someone else]?
[I am not clear as to whose recitation of the performance of an SST propeller is being referenced in this question. Please elaborate on exactly what aspect of the performance of the SST propellers you are inquiring with Crabby about. Thanks--jimh]
tedious posted 12-15-2014 10:37 AM ET (US)
The question I'd have for Crabby is about the performance of the 17 and 19-pitch SSTs he tried - any general information? And specifically with the 19-pitch, were there any signs of what katpil experienced with his current prop, namely relatively high RPMs but still fairly low speed?
Tim
Lil Whaler Lover posted 12-15-2014 04:24 PM ET (US)
It all adds up to the tach being set for a 4 cylinder [engine] currently. Reset it to the correct setting for a 3 cylinder motor. Do this before swapping props and you will find out what your current performance level is.
jimh posted 12-15-2014 06:00 PM ET (US)
The tachometer calibration control is not graduated for the number of cylinders in an engine, but for the number of poles in the alternator winding.
Your reply makes quite an assumption that there is error in the tachometer. How did you determine that the measured engine speed is in error?
katpil posted 12-15-2014 10:52 PM ET (US)
I dont think there's a tachometer [error] here. I had 5,300-RPM at WOT with two large guys on board, 5,650-RPM with one. I think [the cause of the poor boat speed is due to] a [variance or problem or influence from] some sort of disturbed flow and air feeding the propeller when running with a small load. When more heavily loaded the prop is just deep enough in the water that it is not getting that disturbed flow and is performing better. By most opinions I need to move down to a 13.25 x 15 Stiletto and [performance] should be OK. Got some experimenting to do next season!
jimh posted 12-17-2014 05:10 PM ET (US)
I assumed that since the engine speed was reported to 50-RPM the readings were being taken from a digital tachometer linked to the engine management module, and therefore not subject to an error of more than plus or minus 25-RPM. I don't know how or on what basis or from what was presented in the discussion that LIL WHALER LOVER deduced that the entire cause of the problem in performance was due to an error in tachometer reading. He has yet to explain his thinking on that.
I agree with the theory that a propeller can improve its SLIP if running nicely submerged in contrast to running in airy and foamy water. More thrust is created by accelerating solid water than by accelerating airy and foamy water.
crabby posted 12-18-2014 09:25 AM ET (US)
My motor is mounted three holes up (can only be raised one more hole).
The 19 pitch SST was too much prop when I tried it. It would not allow the motor to rev as high as it should have. As for details, well, sorry that was ten years ago and I just don't recall all the details from that time. Perhaps if you do a search on this site you may find better comments I may have made way back when.
I only used the 19 SST a couple of times then replaced it with my old 17 pitch SST (from 1986). This was a well worn prop that served me very well swinging under a 1986 70 hp Evinrude three cylinder engine. This prop actually ran pretty well with the new ETEC but tended to blow out on turns so I figured I would try out the Stiletto.
As soon as I received the 15 pitch Stiletto I mounted it on the new motor and took it for a ride. It had similar performance to the 17 SST as far as top speed and rpm's but refused to blow out even in tight turns. It's still on the rig and has served well.
Lil Whaler Lover posted 12-18-2014 09:53 AM ET (US)
jimh, actually the thought that the tach might be set wrong makes a lot of sense. The rpm reading is high and the speed given is low. This is happening with a prop that is too high in pitch.
An excessive amount of pitch should provide a lower rpm reading, not a higher one. Also this engine could be, or is perhaps lugging as it tries to reach its desired rpm level and horsepower output. This could explain the unusually low reported speed for the rig. Simple math: high pitch should provide less rpm and less speed.
If the rig were mine I would start with the tach to make sure it is accurate and I was getting good data from it.
jimh posted 12-18-2014 10:28 AM ET (US)
"The thought that the tach is wrong" is one explanation for the reported performance data to suggest the propeller has such a high SLIP number, but how did you determine that the tachometer was wrong and was the cause of the problem? In the data we are given measured values for engine speed (RPM) and boat speed (MPH). Any measured value could be in error.
KAPTIL has not given us details about either measurement. Perhaps he can shed some more light on the process used to measure the speeds he reports for engine and boat.
An error is easily possible in speed measured by GPS receiver, since a (typical) GPS receiver does not directly measure speed at all. The typical GPS receiver only deduces a position and then computes speed on the basis of distance and time between position solutions. And it only computes or deduces speed over bottom, never speed through the water. Speed from GPS could be in error if there was any current effect taking place during the measurement run. So we can have concern about the boat speed data. And the accuracy of GPS speed measurement is not absolute, but only as good as the position accuracy. The position accuracy of a run-of-the-mill recreational GPS receiver is not so good to insure that the speed ir computes is precisely accurate.
The engine speed data may be in error, too, of course, but, as I mentioned earlier, since it is reported to a resolution of 50-RPM there is a reasonable inference that this data is from a digital reading of engine speed from the E-TEC engine itself, not from an operator squinting at the analogue dial pointer of a traditional alternator-driven tachometer with a calibration knob that might be set to the wrong number of poles.
crbenny posted 12-18-2014 05:24 PM ET (US)
Crabby, how can you be three holes up and have the ability to go even higher? My E-tec 90 only has 4 sets of holes.
Chris
katpil posted 12-18-2014 10:19 PM ET (US)
As for the measurement instruments and scenarios....
Analog tach, gps for speed, SST 13-7/8 x 19 prop, on a lake, no currents. I think an analog tach can be read to about +/- 25 rpm. So, yes, I would expect some variation with these data inputs, but not as much as I'm seeing.
Test one - the initial shakedown run with the dealer, no gps installed, 5300 rpm at WOT, two good sized men on board.
Test two - 5650 rpm at WOT, GPS speed 39 mph, one person on board.
No electrical changes or tach adjustments made between the two runs. In fact, on the day I had the gps installed I made a half dozen tests at WOT on flat water, minimal wind and about 28F air temp.I ended up with the same 5650 result and never showing more than 39 on the gps.
I've kept all my circa 2002 instrumentation from my 2002 Johnson 90 v4. With the old engine prop set up WOT was always the same, 5300 rpm, 42 to 43 mph. Would one expect to have to make a change to the tach going from a Johnson of that vintage to a new ETEC? I didnt think so.
jimh posted 12-18-2014 11:05 PM ET (US)
Now that the tachometer is revealed to be an old analogue tachometer, and calibration was just presumed, my initial doubts about the accuracy of the engine speed measurment return.
These analogue tachometers usually have a pointer movement of only 90-degrees. There are usually calibration marks to 7,000-RPM. To read them to a resolution of 25-RPM suggests one can measure the dial pointer movement to
(90-degrees / 7,000-RPM ) x 25-RPM = 0.3-degrees
I don't believe you can make repeatable measurement of the dial position to 0.3-degrees of movement.
The scale has seven major devisions for 7,000-RPM, or one major division per 1,000-RPM. That means 25-RPM is 1/40th of a major division. Who can read a tachometer that closely? Not I.
I'd at least inquire about or check on the calibration setting for an E-TEC. I would not assume it is just the same as it was for a non-E-TEC. Even if the calibration setting is properly adjusted, there is no guarantee of really precise accuracy with a 12-year-old analogue tachometer made for a different engine.
katpil posted 12-20-2014 03:02 PM ET (US)
I would agree that the accuracy of the tach is not really known, but with the prior engine set up the tach's precision was very consistent. It always showed the same WOT rpm reading (flat water, one person onboard). I have no reason to doubt its precision with the new installation. But will probably try to get a digital instrument to verify that the analog is close.
I believe both the old and new engines are 12 pole alternator configurations so I dont think I need to make any changes to the tach settings. Is that correct?
I've got some experimenting to do in the spring when the boat is out of its shrink wrap.
Lil Whaler Lover posted 12-26-2014 08:24 PM ET (US)
One more time, an analog tach must be set to the cylinder configuration based on the number of cylinders. The 90 hp Johnson that was removed from service was a V-4. The new 90 E-Tec is a 3 cylinder inline engine. The [two] will not use the same settings on an analog tach. Start there next spring, you may save a lot of time and money.
jimh posted 12-26-2014 08:45 PM ET (US)
Tachometer calibration for two-cycle engines is not based on the number of cylinders.
katpil posted 12-28-2014 06:11 PM ET (US)
I thought the tach was set on the number of alternator poles not number of cylinders. Isnt the ETEC similar to the old V4 when it comes to alternator poles? Also, I would have thought my dealer would have mentioned something to me about that. He ran an installation checklist with the engine at WOT and used the number off the tach for that info.
jimh posted 12-28-2014 08:19 PM ET (US)
KATPIL says:

quote:
I thought the tach was set on the number of alternator poles not number of cylinders.
Your thoughts are correct. I recommend you do not follow advice that says the setting of the tachometer calibration control is made to correspond to the number of cylinders in the engine.
The alternator creates a tachometer signal that corresponds to the rotation of the crankshaft. Whether two cylinders, three cylinders, four cylinders, or six cylinders cause the rotation of the crankshaft, the signal that is generated does not change. The signal is proportional to the rotation of the crankshaft, not to how many cylinders cause it to revolve. The signal is an electrical signal, and corresponds to the alternating-current frequency of the alternator coil windings as rectified by a half-wave rectifier.
The degree of accuracy of a particular tachometer is affected by the setting of its calibration control and likely by other considerations, so there is no guarantee that a particular tachometer connected to a particular engine reads the crankshaft speed precisely accurately.
ratherwhalering posted 01-06-2015 07:34 PM ET (US)
The only accurate way to check the tachometer is to compare it to the RPM on a laptop or PDA using the Evinrude diagnostic software. Ask your dealer to plug it in and take you for a ride.
ratherwhalering posted 01-06-2015 07:42 PM ET (US)
Actually, since the boat is wrapped, you could simply drive it down to the dealer and have her use the Evinrude diagnostic software to determine your engine's highest RPM to date. If it's 5650, your tach is accurate.

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Author	Topic: MONTAUK E-TEC 90
katpil	posted 12-06-2014 03:31 PM ET (US) Late this fall I re-powered my 1990 Montauk with a new E-TEC 90. I am using the old propeller, a SST 13-7/8 x 19, that I had on the prior engine, a 2001 Johnson 90 V4. I ran this propeller for ten years on the old engine and was satisfied with its performance. With the old engine on flat water, WOT, one person onboard, my GPS would show 43-MPH at about 5,300-RPM. On the E-TEC, I'm getting 39-MPH at 5,650 rpm in similar conditions. The E-TEC is mounted fairly high on the transom, two holes showing above the upper mount bolts [which sounds like a two-hole up mounting positing---jimh]. I know that 19-pitch is on the top end for this boat and motor combination. Should I lower the mount position down two holes? Should I be getting a different propeller?
jimh	posted 12-06-2014 03:56 PM ET (US) Your old engine was V4 with more displacement. It may have been more powerful than the three-cylinder in-line new engine. The recommended full-throttle engine speed range for the E-TEC 90 is found at http://continuouswave.com/whaler/reference/ETEC_EngineRPM.html For a recent model E-TEC 90 the optimum range is 5,000 to 5,200-RPM. With your boat and propeller, you are reaching full-throttle speeds that are quite a bit higher than the optimum. My first instinct is to look for a different propeller with a combination of more pitch and perhaps more diameter, so that full-throttle engine speed moves into the recommended range. The engine mounting height is more a function of the particular propeller. Some propellers tolerate higher mounting better than others. Many modern engines run at two-holes-up position with modern propellers. Putting your data into my propeller calculator at http://continuouswave.com/cgi-bin/propcalc.pl shows a calculated SLIP of 13.7-percent, which is a littler higher than usual. (I used 2.25:1 for the gear ratio. Check your owner's manual to see what the gear ratio is on your engine and let us know. Gear ratio is important in propeller selection.) Since the present full-throttle engine speed is 5650 and optimum is 5200, the engine can come down about 400-RPM. That is often indicative of increasing pitch about 2-inches. That would be 21-pitch, which seems like a lot of pitch for the boat. The propeller calculator predicts about 41-MPH for RPM=5200 RATIO=2.25 PITCH=21 SLIP=10 I am also curious about the diameter of your present 19-pitch propeller. It sounds a little small.
katpil	posted 12-06-2014 04:16 PM ET (US) Thanks Jim, The gear ratio is 2:1. I'm hesitant to go over 19" pitch on this motor, seems most are running 17 or 15 on this setup. I was thinking that perhaps the prop is pulling in some air at WOT since its up two holes, I'm used to the old days when engines were mounted all the way down. This motor only has 2 hrs use on it so I'm not really attuned to its sounds and signals yet. But it didnt sound out of the ordinary to me. I may lower it one hole and see what that does. And, just doubled checked, it is a 13 7/8 dia prop.
jimh	posted 12-06-2014 07:29 PM ET (US) RPM=5650 RATIO=2 PITCH=19 MPH=39 SLIP=23.3-percent--TOO HIGH The propeller is not really performing well. http://continuouswave.com/cgi-bin/propcalc.pl Is that speed really in Statute Miles Per Hour?
katpil	posted 12-06-2014 11:36 PM ET (US) I think I'll lower the engine a hole or two and see what happens. That slip number could mean it getting air and disturbed flow from the hull, IMO.
tedious	posted 12-08-2014 02:57 PM ET (US) Unless you are obviously blowing out (such as in turns) there's no need to lower the motor. You need a taller prop, and a better one. The old SSTs were good for their day, but that was a long time ago. I would try something like a Stiletto Advantage in size 13.24x19. That should bring your RPMs down and also provide less slip / better grip. Tim
Alan Heckman	posted 12-08-2014 03:26 PM ET (US) If my memory is correct I think Tom Clarks recommended prop for an ETEC 90 is a Stiletto Advantage 13.25 x 15 mounted 2 holes up. Maybe some of you ETEC guys could verify that. That is on a Montauk 17.
katpil	posted 12-08-2014 10:36 PM ET (US) Perhaps another interesting piece of data.....the day of the installation the dealer took me out for a quick shakedown run. With me standing behind the RPS and him at the wheel, WOT rpms were 5350. I didnt have the GPS so I dont have a speed with that. To me that would indicate the prop was getting a better "bite" with the extra weight in the stern. Has prop technology really changed that much that I should ditch the SST and try a Stiletto?
tedious	posted 12-09-2014 09:01 AM ET (US) Yes, a Stiletto will perform better than your old SST. You didn't specify if it's in good condition - with that level of slip, it almost seems like it must be dinged up a bit, reducing the effective pitch. Either way, going with a Stiletto or other newer-tech prop will improve your performance across the board. You paid a lot for a nice new motor - why handicap it with yesterday's technology when it comes to a prop? You can get the Stiletto from Dan's Discount Props for $279, including the required hubkit. In general, I'd go with Tom Clark's recommendation. I don't think you want to lower the motor or add more weight in the stern unless you're looking to reduce your top speed and burn more gas. Tim
katpil	posted 12-09-2014 01:25 PM ET (US) Thanks for the info Tim. Actually the SST, although I have used it for 12 years is in perfect condition. Except for a bit of fade in the paint it looks new....
Alan Heckman	posted 12-09-2014 01:39 PM ET (US) Just looked some old posts. An ETEC 90 with a Stiletto Advandage 13.25 x 15 mounted 2 holes up gets 41 mph at 5200 rpm. Some people are also running the ETEC 90 3 holes up with good results.
Alan Heckman	posted 12-09-2014 01:45 PM ET (US) Just to clarify my previous post both these mounting heights were using the Stiletto Advantage 13.25 x 15 stainless steel prop.
tedious	posted 12-10-2014 02:02 PM ET (US) Something's not completely adding up. I'm hard pressed to believe that the cupping on the Stiletto more than makes up for the additional 4" of pitch and 5/8" diameter of the SST. SO in theory, katpil should not be able to turn that prop that fast, and if he was, he'd be seeing more top end. Something is causing an extreme amount of slip with the SST. Tim
jimh	posted 12-10-2014 10:02 PM ET (US) I was wondering about the tachometer accuracy, but, since the value is given to 50-RPM, I presume it is a digital readout from NMEA-2000 engine data. That is usually precisely accurate engine speed.
katpil	posted 12-10-2014 10:16 PM ET (US) Agree, something isnt stacking up. I'll be doing some experimenting this spring on flat water. Need to experiment with trim and see if this set up turns correctly, etc. I'm just thinking that with the extra person on board the transom was deeper in the water allowing the SST to get a better "bite".
tedious	posted 12-11-2014 08:09 AM ET (US) Getting more bite is where the modern props like Stiletto excel - I don't know how to describe it, but it just feels like it's gripping the water better in all conditions. Tim
crabby	posted 12-11-2014 10:11 AM ET (US) You either need a 17 inch pitch SST or the 15 inch pitch Stiletto as recommended above. My Montauk is a 1985 with a 2004 90hp ETEC swinging the 15 inch Stiletto (after trialing both 17 and 19 inch pitch SST props when I first hung the motor back in 2004).
katpil	posted 12-11-2014 07:05 PM ET (US) Crabby....did you have the same [performance] with the SST props [as someone else]? [I am not clear as to whose recitation of the performance of an SST propeller is being referenced in this question. Please elaborate on exactly what aspect of the performance of the SST propellers you are inquiring with Crabby about. Thanks--jimh]
tedious	posted 12-15-2014 10:37 AM ET (US) The question I'd have for Crabby is about the performance of the 17 and 19-pitch SSTs he tried - any general information? And specifically with the 19-pitch, were there any signs of what katpil experienced with his current prop, namely relatively high RPMs but still fairly low speed? Tim
Lil Whaler Lover	posted 12-15-2014 04:24 PM ET (US) It all adds up to the tach being set for a 4 cylinder [engine] currently. Reset it to the correct setting for a 3 cylinder motor. Do this before swapping props and you will find out what your current performance level is.
jimh	posted 12-15-2014 06:00 PM ET (US) The tachometer calibration control is not graduated for the number of cylinders in an engine, but for the number of poles in the alternator winding. Your reply makes quite an assumption that there is error in the tachometer. How did you determine that the measured engine speed is in error?
katpil	posted 12-15-2014 10:52 PM ET (US) I dont think there's a tachometer [error] here. I had 5,300-RPM at WOT with two large guys on board, 5,650-RPM with one. I think [the cause of the poor boat speed is due to] a [variance or problem or influence from] some sort of disturbed flow and air feeding the propeller when running with a small load. When more heavily loaded the prop is just deep enough in the water that it is not getting that disturbed flow and is performing better. By most opinions I need to move down to a 13.25 x 15 Stiletto and [performance] should be OK. Got some experimenting to do next season!
jimh	posted 12-17-2014 05:10 PM ET (US) I assumed that since the engine speed was reported to 50-RPM the readings were being taken from a digital tachometer linked to the engine management module, and therefore not subject to an error of more than plus or minus 25-RPM. I don't know how or on what basis or from what was presented in the discussion that LIL WHALER LOVER deduced that the entire cause of the problem in performance was due to an error in tachometer reading. He has yet to explain his thinking on that. I agree with the theory that a propeller can improve its SLIP if running nicely submerged in contrast to running in airy and foamy water. More thrust is created by accelerating solid water than by accelerating airy and foamy water.
crabby	posted 12-18-2014 09:25 AM ET (US) My motor is mounted three holes up (can only be raised one more hole). The 19 pitch SST was too much prop when I tried it. It would not allow the motor to rev as high as it should have. As for details, well, sorry that was ten years ago and I just don't recall all the details from that time. Perhaps if you do a search on this site you may find better comments I may have made way back when. I only used the 19 SST a couple of times then replaced it with my old 17 pitch SST (from 1986). This was a well worn prop that served me very well swinging under a 1986 70 hp Evinrude three cylinder engine. This prop actually ran pretty well with the new ETEC but tended to blow out on turns so I figured I would try out the Stiletto. As soon as I received the 15 pitch Stiletto I mounted it on the new motor and took it for a ride. It had similar performance to the 17 SST as far as top speed and rpm's but refused to blow out even in tight turns. It's still on the rig and has served well.
Lil Whaler Lover	posted 12-18-2014 09:53 AM ET (US) jimh, actually the thought that the tach might be set wrong makes a lot of sense. The rpm reading is high and the speed given is low. This is happening with a prop that is too high in pitch. An excessive amount of pitch should provide a lower rpm reading, not a higher one. Also this engine could be, or is perhaps lugging as it tries to reach its desired rpm level and horsepower output. This could explain the unusually low reported speed for the rig. Simple math: high pitch should provide less rpm and less speed. If the rig were mine I would start with the tach to make sure it is accurate and I was getting good data from it.
jimh	posted 12-18-2014 10:28 AM ET (US) "The thought that the tach is wrong" is one explanation for the reported performance data to suggest the propeller has such a high SLIP number, but how did you determine that the tachometer was wrong and was the cause of the problem? In the data we are given measured values for engine speed (RPM) and boat speed (MPH). Any measured value could be in error. KAPTIL has not given us details about either measurement. Perhaps he can shed some more light on the process used to measure the speeds he reports for engine and boat. An error is easily possible in speed measured by GPS receiver, since a (typical) GPS receiver does not directly measure speed at all. The typical GPS receiver only deduces a position and then computes speed on the basis of distance and time between position solutions. And it only computes or deduces speed over bottom, never speed through the water. Speed from GPS could be in error if there was any current effect taking place during the measurement run. So we can have concern about the boat speed data. And the accuracy of GPS speed measurement is not absolute, but only as good as the position accuracy. The position accuracy of a run-of-the-mill recreational GPS receiver is not so good to insure that the speed ir computes is precisely accurate. The engine speed data may be in error, too, of course, but, as I mentioned earlier, since it is reported to a resolution of 50-RPM there is a reasonable inference that this data is from a digital reading of engine speed from the E-TEC engine itself, not from an operator squinting at the analogue dial pointer of a traditional alternator-driven tachometer with a calibration knob that might be set to the wrong number of poles.
crbenny	posted 12-18-2014 05:24 PM ET (US) Crabby, how can you be three holes up and have the ability to go even higher? My E-tec 90 only has 4 sets of holes. Chris
katpil	posted 12-18-2014 10:19 PM ET (US) As for the measurement instruments and scenarios.... Analog tach, gps for speed, SST 13-7/8 x 19 prop, on a lake, no currents. I think an analog tach can be read to about +/- 25 rpm. So, yes, I would expect some variation with these data inputs, but not as much as I'm seeing. Test one - the initial shakedown run with the dealer, no gps installed, 5300 rpm at WOT, two good sized men on board. Test two - 5650 rpm at WOT, GPS speed 39 mph, one person on board. No electrical changes or tach adjustments made between the two runs. In fact, on the day I had the gps installed I made a half dozen tests at WOT on flat water, minimal wind and about 28F air temp.I ended up with the same 5650 result and never showing more than 39 on the gps. I've kept all my circa 2002 instrumentation from my 2002 Johnson 90 v4. With the old engine prop set up WOT was always the same, 5300 rpm, 42 to 43 mph. Would one expect to have to make a change to the tach going from a Johnson of that vintage to a new ETEC? I didnt think so.
jimh	posted 12-18-2014 11:05 PM ET (US) Now that the tachometer is revealed to be an old analogue tachometer, and calibration was just presumed, my initial doubts about the accuracy of the engine speed measurment return. These analogue tachometers usually have a pointer movement of only 90-degrees. There are usually calibration marks to 7,000-RPM. To read them to a resolution of 25-RPM suggests one can measure the dial pointer movement to (90-degrees / 7,000-RPM ) x 25-RPM = 0.3-degrees I don't believe you can make repeatable measurement of the dial position to 0.3-degrees of movement. The scale has seven major devisions for 7,000-RPM, or one major division per 1,000-RPM. That means 25-RPM is 1/40th of a major division. Who can read a tachometer that closely? Not I. I'd at least inquire about or check on the calibration setting for an E-TEC. I would not assume it is just the same as it was for a non-E-TEC. Even if the calibration setting is properly adjusted, there is no guarantee of really precise accuracy with a 12-year-old analogue tachometer made for a different engine.
katpil	posted 12-20-2014 03:02 PM ET (US) I would agree that the accuracy of the tach is not really known, but with the prior engine set up the tach's precision was very consistent. It always showed the same WOT rpm reading (flat water, one person onboard). I have no reason to doubt its precision with the new installation. But will probably try to get a digital instrument to verify that the analog is close. I believe both the old and new engines are 12 pole alternator configurations so I dont think I need to make any changes to the tach settings. Is that correct? I've got some experimenting to do in the spring when the boat is out of its shrink wrap.
Lil Whaler Lover	posted 12-26-2014 08:24 PM ET (US) One more time, an analog tach must be set to the cylinder configuration based on the number of cylinders. The 90 hp Johnson that was removed from service was a V-4. The new 90 E-Tec is a 3 cylinder inline engine. The [two] will not use the same settings on an analog tach. Start there next spring, you may save a lot of time and money.
jimh	posted 12-26-2014 08:45 PM ET (US) Tachometer calibration for two-cycle engines is not based on the number of cylinders.
katpil	posted 12-28-2014 06:11 PM ET (US) I thought the tach was set on the number of alternator poles not number of cylinders. Isnt the ETEC similar to the old V4 when it comes to alternator poles? Also, I would have thought my dealer would have mentioned something to me about that. He ran an installation checklist with the engine at WOT and used the number off the tach for that info.
jimh	posted 12-28-2014 08:19 PM ET (US) KATPIL says: quote: I thought the tach was set on the number of alternator poles not number of cylinders. Your thoughts are correct. I recommend you do not follow advice that says the setting of the tachometer calibration control is made to correspond to the number of cylinders in the engine. The alternator creates a tachometer signal that corresponds to the rotation of the crankshaft. Whether two cylinders, three cylinders, four cylinders, or six cylinders cause the rotation of the crankshaft, the signal that is generated does not change. The signal is proportional to the rotation of the crankshaft, not to how many cylinders cause it to revolve. The signal is an electrical signal, and corresponds to the alternating-current frequency of the alternator coil windings as rectified by a half-wave rectifier. The degree of accuracy of a particular tachometer is affected by the setting of its calibration control and likely by other considerations, so there is no guarantee that a particular tachometer connected to a particular engine reads the crankshaft speed precisely accurately.
ratherwhalering	posted 01-06-2015 07:34 PM ET (US) The only accurate way to check the tachometer is to compare it to the RPM on a laptop or PDA using the Evinrude diagnostic software. Ask your dealer to plug it in and take you for a ride.
ratherwhalering	posted 01-06-2015 07:42 PM ET (US) Actually, since the boat is wrapped, you could simply drive it down to the dealer and have her use the Evinrude diagnostic software to determine your engine's highest RPM to date. If it's 5650, your tach is accurate.