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Author Topic:   New OptiMax Starts Faster

sosmerc posted 04-09-2008 10:08 PM ET (US)
I just completed the installation of a new Optimax 115XL and noticed something different. After the engine was warmed up, I shut it off and then immediately restarted. What I noticed was that the engine started IMMEDIATELY at just a flick of the key. In the past, I have observed that the engine needed to crank over for what seemed to be a set period of time before the engine would start, regardless of whether warm or cold. It was my understanding that at least 2 complete revolutions of the flywheel were required (giving the engine computer time to receive data from all the sensors) before the engine would attempt to start. This is one of the reasons that Merc recommends a very strong (1000 MCA) starting battery be used with all Optimax models. But it appears that maybe they have changed their strategy. This particular engine restarted immediately...it couldn't have even made one revolution of the flywheel before it fired up. I wonder if this is a new strategy that will apply to all NEW Optimax engines??
jimh posted 04-10-2008 12:01 AM ET (US)
sos--That is an interesting observation. My reaction is this wild guess:
Perhaps the engine controller has been upgraded so that it can get the crankshaft position deduced faster and fire the first cylinder earlier.
Electronic processors have been getting faster and cheaper. Perhaps there is a new generation of those PCM555 controllers out there.
sosmerc posted 04-10-2008 01:11 AM ET (US)
That could be. I would also think that, with years of experience under their belt now, perhaps the computer doesn't need to collect quite as much information before knowing what to do to start the engine every time. This saves battery power, which to some, has been an concern with Optimax. The need for strong batteries considered essential.
JayR posted 04-10-2008 05:03 AM ET (US)
Are you suggesting a stronger battery is no longer needed?
XStech posted 04-10-2008 12:56 PM ET (US)
The OptiMax ECU only needs 30° of crank rotation to know where it is.
OptiMax motors have what is called pump-up. This is when the ECU holds open the air injectors during crank as the piston comes up on TDC to help the air compressor come up to pressure. This pump-up time will vary by the number of cylinder events depending on the temp of the motor. Cold = longer, warm = shorter. During pump-up, the motor will not attempt to start. This is the start delay you see in an OptiMax.
They may have shortend this on the new models.
sosmerc posted 04-10-2008 01:18 PM ET (US)
This MAY only apply to the 3 cylinder models. With only one fuel-air rail to pressurize less time is needed. I'm pretty sure the 1,000-MCA minimum battery recommendation has NOT been changed.
This motor was installed on about an 18-foot Olympic cabin model boat with a GIL bracket. The engine is an XL model and replaced a 1987 115-HP In-line Six Mercury. I am eager to see how the performance compares. We thought about going to a 135 OptiMax, but I suggested the 115 OptiMax to try and keep the weight down.
I am particular interested to see how this setup works as I am considering "downsizing" from a 135hp OptiMax on my 18ft. Ventura. I like the simplicity of the three-cylinder OptiMax motors along with their smooth, quiet and fuel stingy operation. I only wish they were DTS as well.
Tohsgib posted 04-10-2008 01:23 PM ET (US)
3cyl 115hp--how much displacement is it? Sounds a tad high strung for 3 pots.
jimh posted 04-10-2008 05:41 PM ET (US)
Mercury's recommendation for a large capacity battery to be used with their OptiMax motors is most likely concern that the battery terminal voltage will sag during cranking. If the voltage sags too low then the processor may reboot or other electronic devices which are depending on the battery may be affected. It is not related to processor speed. It is related to how the processor power is provided.
sosmerc posted 04-10-2008 09:01 PM ET (US)
The 3 cylinder 75/90/115 Optimax was created by using 1/2 of the 3.0 litre. It is 1.5 litre. The cylinder head is cast as part of the block...no head gasket or o-rings to worry about. Nice tight design.
fourdfish posted 04-10-2008 11:03 PM ET (US)
To XStech: if they did shorten the start delay, why are you not aware of it?
XStech posted 04-11-2008 07:48 AM ET (US)
fourdfish
Because I have not talked to "they" about it, nor have I taken the time to open up and look at "they's" cal.
jimh posted 04-11-2008 08:57 AM ET (US)
XStech--Thanks for the explanation. It sounds like a new control algorithm for the ECU.
sosmerc posted 04-12-2008 10:53 PM ET (US)
Water tested the boat today. I am quite satisfied with the power of this engine...and it is very quiet and fuel efficient as well. 3.0 gph at 3000 rpm, about 4.6 gph at 4600.
I am convinced this engine would perform quite adequately on my 18ft. Ventura...though clearly would not be as fast as a 135 Opti or the 200 DFI that I now have on the boat.
The new owner was quite impressed.....in comparison to his previous 1986 115 inline six.
sosmerc posted 04-13-2008 03:41 PM ET (US)
Just thinking out loud here.....
Boston Whaler says 115hp is the minumum recommended hp for the 18ft. Ventura like I have.
The 115 Optimax is the same engine as the 90hp Optimax only the 90 has a 2.3 to 1 gear ratio compared to the 2 to 1 gear ratio used on the 115.
I'm thinking that the 90hp might actually do a better job of getting the boat on plane due to the gear ratio. Yes, the 115 would be faster on the top end, but if top speed is not a concern perhaps the 90 Optimax would actually be a better choice?
Any thoughts?
(I have run the boat several seasons with a 135 Optimax...and I currently just installed a 1997 3.0 litre Merc DFI just for kicks. I'd actually like to "down-size" for improved fuel economy and also would like a newer engine for better reliability and peace of mind)

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Author	Topic: New OptiMax Starts Faster
sosmerc	posted 04-09-2008 10:08 PM ET (US) I just completed the installation of a new Optimax 115XL and noticed something different. After the engine was warmed up, I shut it off and then immediately restarted. What I noticed was that the engine started IMMEDIATELY at just a flick of the key. In the past, I have observed that the engine needed to crank over for what seemed to be a set period of time before the engine would start, regardless of whether warm or cold. It was my understanding that at least 2 complete revolutions of the flywheel were required (giving the engine computer time to receive data from all the sensors) before the engine would attempt to start. This is one of the reasons that Merc recommends a very strong (1000 MCA) starting battery be used with all Optimax models. But it appears that maybe they have changed their strategy. This particular engine restarted immediately...it couldn't have even made one revolution of the flywheel before it fired up. I wonder if this is a new strategy that will apply to all NEW Optimax engines??
jimh	posted 04-10-2008 12:01 AM ET (US) sos--That is an interesting observation. My reaction is this wild guess: Perhaps the engine controller has been upgraded so that it can get the crankshaft position deduced faster and fire the first cylinder earlier. Electronic processors have been getting faster and cheaper. Perhaps there is a new generation of those PCM555 controllers out there.
sosmerc	posted 04-10-2008 01:11 AM ET (US) That could be. I would also think that, with years of experience under their belt now, perhaps the computer doesn't need to collect quite as much information before knowing what to do to start the engine every time. This saves battery power, which to some, has been an concern with Optimax. The need for strong batteries considered essential.
JayR	posted 04-10-2008 05:03 AM ET (US) Are you suggesting a stronger battery is no longer needed?
XStech	posted 04-10-2008 12:56 PM ET (US) The OptiMax ECU only needs 30° of crank rotation to know where it is. OptiMax motors have what is called pump-up. This is when the ECU holds open the air injectors during crank as the piston comes up on TDC to help the air compressor come up to pressure. This pump-up time will vary by the number of cylinder events depending on the temp of the motor. Cold = longer, warm = shorter. During pump-up, the motor will not attempt to start. This is the start delay you see in an OptiMax. They may have shortend this on the new models.
sosmerc	posted 04-10-2008 01:18 PM ET (US) This MAY only apply to the 3 cylinder models. With only one fuel-air rail to pressurize less time is needed. I'm pretty sure the 1,000-MCA minimum battery recommendation has NOT been changed. This motor was installed on about an 18-foot Olympic cabin model boat with a GIL bracket. The engine is an XL model and replaced a 1987 115-HP In-line Six Mercury. I am eager to see how the performance compares. We thought about going to a 135 OptiMax, but I suggested the 115 OptiMax to try and keep the weight down. I am particular interested to see how this setup works as I am considering "downsizing" from a 135hp OptiMax on my 18ft. Ventura. I like the simplicity of the three-cylinder OptiMax motors along with their smooth, quiet and fuel stingy operation. I only wish they were DTS as well.
Tohsgib	posted 04-10-2008 01:23 PM ET (US) 3cyl 115hp--how much displacement is it? Sounds a tad high strung for 3 pots.
jimh	posted 04-10-2008 05:41 PM ET (US) Mercury's recommendation for a large capacity battery to be used with their OptiMax motors is most likely concern that the battery terminal voltage will sag during cranking. If the voltage sags too low then the processor may reboot or other electronic devices which are depending on the battery may be affected. It is not related to processor speed. It is related to how the processor power is provided.
sosmerc	posted 04-10-2008 09:01 PM ET (US) The 3 cylinder 75/90/115 Optimax was created by using 1/2 of the 3.0 litre. It is 1.5 litre. The cylinder head is cast as part of the block...no head gasket or o-rings to worry about. Nice tight design.
fourdfish	posted 04-10-2008 11:03 PM ET (US) To XStech: if they did shorten the start delay, why are you not aware of it?
XStech	posted 04-11-2008 07:48 AM ET (US) fourdfish Because I have not talked to "they" about it, nor have I taken the time to open up and look at "they's" cal.
jimh	posted 04-11-2008 08:57 AM ET (US) XStech--Thanks for the explanation. It sounds like a new control algorithm for the ECU.
sosmerc	posted 04-12-2008 10:53 PM ET (US) Water tested the boat today. I am quite satisfied with the power of this engine...and it is very quiet and fuel efficient as well. 3.0 gph at 3000 rpm, about 4.6 gph at 4600. I am convinced this engine would perform quite adequately on my 18ft. Ventura...though clearly would not be as fast as a 135 Opti or the 200 DFI that I now have on the boat. The new owner was quite impressed.....in comparison to his previous 1986 115 inline six.
sosmerc	posted 04-13-2008 03:41 PM ET (US) Just thinking out loud here..... Boston Whaler says 115hp is the minumum recommended hp for the 18ft. Ventura like I have. The 115 Optimax is the same engine as the 90hp Optimax only the 90 has a 2.3 to 1 gear ratio compared to the 2 to 1 gear ratio used on the 115. I'm thinking that the 90hp might actually do a better job of getting the boat on plane due to the gear ratio. Yes, the 115 would be faster on the top end, but if top speed is not a concern perhaps the 90 Optimax would actually be a better choice? Any thoughts? (I have run the boat several seasons with a 135 Optimax...and I currently just installed a 1997 3.0 litre Merc DFI just for kicks. I'd actually like to "down-size" for improved fuel economy and also would like a newer engine for better reliability and peace of mind)