2001 Mercury 90: Maximum RPM 2,600 - Moderated Discussion Areas

  ContinuousWave
  Whaler
  Moderated Discussion Areas
  ContinuousWave: Whaler Repairs/Mods
  2001 Mercury 90: Maximum RPM 2,600

search | FAQ | profile | register | author help

Author Topic:   2001 Mercury 90: Maximum RPM 2,600

bmedlin posted 08-16-2014 06:01 PM ET (US)
My 2001 Mercruy 90-HP outboard maximum speed is 2,600-RPM in forward, and only forward. Any help to this would be appreciated.
[Please give the URL to any other articles you want to make reference.--jimh]
Ltsimp posted 08-16-2014 07:28 PM ET (US)
Is it an Optimax?
bmedlin posted 08-16-2014 07:49 PM ET (US)
No. [The engine being discussed] is not [an OptiMax].
saumon posted 08-16-2014 09:39 PM ET (US)
What kind of engine it is? In 2001, Mercury made 90-HP engines in both traditional two-stroke, that is, not OptiMax, and in four-stroke. I had the same problem on a 1993 Mercury 60-HP two-cycle in-line three-cylinder. I traced down the cause to fuel delivery: punctured fuel pump diaphragm. Easy repair. What seems weird in your case is the fact that the problem arise only in forward gear, meaning you could rev it up past that rpm in reverse.
jimh posted 08-16-2014 10:09 PM ET (US)
The crankshaft speed of a two-cycle engine running in neutral with no load is generally of no diagnostic value, as most engines will accelerate to 6,000-RPM or more, often with damaging results, if allowed to be operated at full throttle in neutral with no load.
The maximum crankshaft speed under load in gear in forward should fall into the manufacturer's recommended full-throttle range of speed.
Off hand, I suspect a Mercury 90-HP two-cycle ought to be able to reach 5,000-RPM under load at full throttle. There are many possible causes for the engine being unable to achieve that speed, organized in two general areas:
--the load on the engine is too great, or
--the engine is not able to develop its full power.
Since you have not provided any details about the engine's load, we can't really know which general area is likely to be the cause. Give us more details about the engine, and about the boat and propeller.
saumon posted 08-16-2014 11:29 PM ET (US)
An easy way to test the fuel pump is to squeeze the fuel primer bulb (or have someone else doing it) while giving some throttle, in gear and on the water. If the engine pick up speed, you likely have a defective fuel pump.
bmedlin posted 08-16-2014 11:29 PM ET (US)
This is a 2001 Mercury 90-HP two-stroke [not OptiMax] outboard. I had the boat out earlier that day and it ran great. Brought it back to the dock, had some lunch and was going back out. When I went back out the boat would not plane and would only top out at 2,600-RPM when it would usually top out at 5,000-RPM as it did earlier that day. No [malfunction] in neutral and reverse.
I have the same engine and exact same symptoms as bigmac did in an seven-year-old thread. Unfortunately he never told us what fixed his [engine's malfunction].
bmedlin posted 08-16-2014 11:30 PM ET (US)
Saumon, tomorrow I will try [using the primer bulb to pump fuel to the engine].
bmedlin posted 08-16-2014 11:33 PM ET (US)
The load has not changed so it is definitely that the motor will not power up for some reason. I have changed spark plugs and hooked up the engine directly to an extra fuel tank with a new primer bulb. The engine still would only max out at 2,600-RPM.
jimh posted 08-17-2014 06:38 AM ET (US)
bmedlin--Thank you for giving us more details about the problem you are having with the engine.
jimh posted 08-17-2014 07:07 AM ET (US)
A three-cylinder engine that has lost one cylinder will show a marked reduction in total power output under load but will idle fine.
You can make a simple test to see if all three cylinders are firing. Pull the spark plug wire from one cylinder at a time. Watch for change in engine speed. This test can show if one cylinder is not firing. It does not confirm that the problem is spark related.
To test for spark on each cylinder, use an in-line spark tester.
If all cylinders have good spark, but one cylinder can have its spark plug wire pulled without affecting engine speed, that cylinder is not firing. The cause may be related to lack of fuel. Check the carburetor for that cylinder.
This simple spark plug pull test should allow you to isolate the problem to an individual cylinder.
outragesteve posted 08-17-2014 07:05 PM ET (US)
I'm guessing stator problem. Very easy to test with a Volt-Ohm meter. The procedure can be found all over the internet. Good luck [finding the procedure or finding the cause]
bmedlin posted 08-17-2014 10:20 PM ET (US)
Bigmac got back to me and said his problem was the spark pack which I think he is referring to the CDM module on a Mercury outboard. How can I test a CDM module?
saumon posted 08-17-2014 10:57 PM ET (US)
The common name for the "spark pack" is "switchbox". For a lot of tests related to the electrical components, you'll need a direct-voltage adapter:
http://1manual.com/Mercury%20manuals/Service%20Manual%20PDFs/TwoStroke/ 13645_2/2a.pdf
jimh posted 08-17-2014 10:58 PM ET (US)
How many different names are there for the module that generates the spark in a Mercury engine? So far I have heard:
--switch box
--ignition pack
--CDM
--spark pack
It took about two minutes of browsing the CDI website to find this procedure to test the switch box nee ignition pack nee CDM nee spark pack assembly:
http://www.cdielectronics.com/wp-content/uploads/2013/09/IS-114-7509.pdf
It would be simpler if the number of names used to describe this part were a smaller number.
bmedlin posted 08-18-2014 09:00 AM ET (US)
Thanks for all the help. Can't get back to my engine till probably the weekend. Will update then.
sosmerc posted 08-22-2014 09:27 PM ET (US)
Just a friendly reminder, with regards to discussing Mercury parts, it is always important (and required) to post the engine serial number. With regards to the naming of specific Mercury ignition components, their components are not always exactly the same so what might "look" like a coil, in many cases is a "cdm module" which is in effect, a combination coil and switchbox all in one component. In certain model years, Merc may have made several different production runs of a certain hp. model, and thus the ignition components used may be completely different. The only way to know is to look up parts by serial number of the engine.

Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.

Author	Topic: 2001 Mercury 90: Maximum RPM 2,600
bmedlin	posted 08-16-2014 06:01 PM ET (US) My 2001 Mercruy 90-HP outboard maximum speed is 2,600-RPM in forward, and only forward. Any help to this would be appreciated. [Please give the URL to any other articles you want to make reference.--jimh]
Ltsimp	posted 08-16-2014 07:28 PM ET (US) Is it an Optimax?
bmedlin	posted 08-16-2014 07:49 PM ET (US) No. [The engine being discussed] is not [an OptiMax].
saumon	posted 08-16-2014 09:39 PM ET (US) What kind of engine it is? In 2001, Mercury made 90-HP engines in both traditional two-stroke, that is, not OptiMax, and in four-stroke. I had the same problem on a 1993 Mercury 60-HP two-cycle in-line three-cylinder. I traced down the cause to fuel delivery: punctured fuel pump diaphragm. Easy repair. What seems weird in your case is the fact that the problem arise only in forward gear, meaning you could rev it up past that rpm in reverse.
jimh	posted 08-16-2014 10:09 PM ET (US) The crankshaft speed of a two-cycle engine running in neutral with no load is generally of no diagnostic value, as most engines will accelerate to 6,000-RPM or more, often with damaging results, if allowed to be operated at full throttle in neutral with no load. The maximum crankshaft speed under load in gear in forward should fall into the manufacturer's recommended full-throttle range of speed. Off hand, I suspect a Mercury 90-HP two-cycle ought to be able to reach 5,000-RPM under load at full throttle. There are many possible causes for the engine being unable to achieve that speed, organized in two general areas: --the load on the engine is too great, or --the engine is not able to develop its full power. Since you have not provided any details about the engine's load, we can't really know which general area is likely to be the cause. Give us more details about the engine, and about the boat and propeller.
saumon	posted 08-16-2014 11:29 PM ET (US) An easy way to test the fuel pump is to squeeze the fuel primer bulb (or have someone else doing it) while giving some throttle, in gear and on the water. If the engine pick up speed, you likely have a defective fuel pump.
bmedlin	posted 08-16-2014 11:29 PM ET (US) This is a 2001 Mercury 90-HP two-stroke [not OptiMax] outboard. I had the boat out earlier that day and it ran great. Brought it back to the dock, had some lunch and was going back out. When I went back out the boat would not plane and would only top out at 2,600-RPM when it would usually top out at 5,000-RPM as it did earlier that day. No [malfunction] in neutral and reverse. I have the same engine and exact same symptoms as bigmac did in an seven-year-old thread. Unfortunately he never told us what fixed his [engine's malfunction].
bmedlin	posted 08-16-2014 11:30 PM ET (US) Saumon, tomorrow I will try [using the primer bulb to pump fuel to the engine].
bmedlin	posted 08-16-2014 11:33 PM ET (US) The load has not changed so it is definitely that the motor will not power up for some reason. I have changed spark plugs and hooked up the engine directly to an extra fuel tank with a new primer bulb. The engine still would only max out at 2,600-RPM.
jimh	posted 08-17-2014 06:38 AM ET (US) bmedlin--Thank you for giving us more details about the problem you are having with the engine.
jimh	posted 08-17-2014 07:07 AM ET (US) A three-cylinder engine that has lost one cylinder will show a marked reduction in total power output under load but will idle fine. You can make a simple test to see if all three cylinders are firing. Pull the spark plug wire from one cylinder at a time. Watch for change in engine speed. This test can show if one cylinder is not firing. It does not confirm that the problem is spark related. To test for spark on each cylinder, use an in-line spark tester. If all cylinders have good spark, but one cylinder can have its spark plug wire pulled without affecting engine speed, that cylinder is not firing. The cause may be related to lack of fuel. Check the carburetor for that cylinder. This simple spark plug pull test should allow you to isolate the problem to an individual cylinder.
outragesteve	posted 08-17-2014 07:05 PM ET (US) I'm guessing stator problem. Very easy to test with a Volt-Ohm meter. The procedure can be found all over the internet. Good luck [finding the procedure or finding the cause]
bmedlin	posted 08-17-2014 10:20 PM ET (US) Bigmac got back to me and said his problem was the spark pack which I think he is referring to the CDM module on a Mercury outboard. How can I test a CDM module?
saumon	posted 08-17-2014 10:57 PM ET (US) The common name for the "spark pack" is "switchbox". For a lot of tests related to the electrical components, you'll need a direct-voltage adapter: http://1manual.com/Mercury%20manuals/Service%20Manual%20PDFs/TwoStroke/ 13645_2/2a.pdf
jimh	posted 08-17-2014 10:58 PM ET (US) How many different names are there for the module that generates the spark in a Mercury engine? So far I have heard: --switch box --ignition pack --CDM --spark pack It took about two minutes of browsing the CDI website to find this procedure to test the switch box nee ignition pack nee CDM nee spark pack assembly: http://www.cdielectronics.com/wp-content/uploads/2013/09/IS-114-7509.pdf It would be simpler if the number of names used to describe this part were a smaller number.
bmedlin	posted 08-18-2014 09:00 AM ET (US) Thanks for all the help. Can't get back to my engine till probably the weekend. Will update then.
sosmerc	posted 08-22-2014 09:27 PM ET (US) Just a friendly reminder, with regards to discussing Mercury parts, it is always important (and required) to post the engine serial number. With regards to the naming of specific Mercury ignition components, their components are not always exactly the same so what might "look" like a coil, in many cases is a "cdm module" which is in effect, a combination coil and switchbox all in one component. In certain model years, Merc may have made several different production runs of a certain hp. model, and thus the ignition components used may be completely different. The only way to know is to look up parts by serial number of the engine.