Running Engine In the Water to Check Ignition Timing and Throttle Linkage Settings

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Author Topic:   Running Engine In the Water to Check Ignition Timing and Throttle Linkage Settings

gmoulder posted 12-09-2009 11:17 AM ET (US)
The Seloc manual that I have states many times that the boat must be in the water and under load to accurately check and set the timing and throttle linkage. The repair shop that works on the boat generally does good work, I think. They seem to be intelligent thoughtful guys who want to do a good job. The repair shop says that the Seloc people don't have it right, and that there is no need for in the water tuning. Being a mechanical engineer by trade, I generally trust written published procedures. What is going on here?
tedious posted 12-09-2009 12:49 PM ET (US)
I have found that the aftermarket manuals are generally not that great - OEM is best if you can find it. The OEM manual for that motor also says that you need to be in the water to set the idle speed correctly. However, your mechanics have probably learned through experience that in most cases, setting the idle speed somewhat higher on the muffs gives the right idle speed on the water. The other procedure that, per the manual, needs to be done on the water is setting the WOT timing, but there is a way to get that pretty close to correct while just cranking the motor.
The bottom line is that if the mechanics are experienced with this very popular motor, I would trust them more than the aftermarket manual.
The local mechanic I have spoken with, who has lots of experience with these motors, sets them up in the shop and then goes out for a water test. He indicates it's very rare that he has to make an on-the-water adjustment to get it right.
Tim
gmoulder posted 12-09-2009 05:09 PM ET (US)
Tedious. Thanks, I feel better already about the efforts of repair shop. Would feel even better to have a knowledgable person tune it in the water. As for the repair manual, I have been needing some fire starter this winter.
brisboats posted 12-09-2009 08:12 PM ET (US)
The three cylinder loop charged engine has a large variance between idle speed in and out of water. It would be nice to say that the variance was a consistent 400 rpms for all engines but each engine is a little different so to get it perfect I would want the engine in the water.
The WOT timing can be properly done in a test tank with a test wheel. It is very hard and dangerous to run a boat in open water at WOT with the cowl off and aim a timing light at the pointer all at the same time. Static timing the engine and a proper sync and link may get it right most times but not always. The shop that tunes out of water uses their customers for the water testing segment.
Brian
modenacart posted 12-09-2009 09:07 PM ET (US)
I would think there would be variation depending on which hull the engine was on, thus making it very difficult for the OEM to set a limit for the idle speed outside of the water. I would do what the OEM says, usually the engineers are pretty smart and have a reason for why they recommend what they do.
jimh posted 12-10-2009 09:47 AM ET (US)
I have used a test wheel and checked my ignition timing while running my 225-HP two-cycle outboard engine at a dock. I discovered two important conditions which I had not anticipated:
--running a 225-HP engine at near full throttle at a dock creates an enormous amount of noise, and
--running a 225-HP engine at near full throttle at a dock creates an enormous amount of exhaust smoke.
These two factors were unanticipated. My test drew a crowd of on-lookers to see if my engine was on fire or had gone into a runaway condition. After verifying the ignition time was within one degree of the recommended spark advance, I terminated the test.
To check the ignition timing at full throttle you need an environment for the engine where it can run safely at high speed. Usually a test propeller or test wheel is used to create a load. Be prepared for a lot of noise and smoke.
Tom W Clark posted 12-10-2009 10:23 AM ET (US)
I would hesitate to pay money to an outboard mechanic that did not have a test tank and appropriate test wheels. Using one is standard operating procedure.
My mechanic has three test tanks in his shop. Two of them are on wheels.
tedious posted 12-10-2009 01:47 PM ET (US)
Although doing things perfectly by the manual, including tank testing with a test wheel for WOT timing, would always be preferable, I suspect it's a rare mechanic that has test wheels available for whatever motor the customer comes in with. Tom, you seem to have found a good one, but it's a long commute...
I would point out that the original object of this discussion, the vintage OMC 70 triple, is a fairly blunt instrument. Being off by a bit on the idle speed isn't going to make a whole lot of difference. And in practice, once WOT timing is set right, it shouldn't need adjustment - it's just a mechanical stop that limits the travel of the timer base, not something that is going to wear or go out of calibration. That may not be true for other motors.
Good story about smoking up the dock, Jim - I did get at test wheel for my 70 (couldn't pass up deal on eBay) but I have not tried it yet. I will alert the fire department in advance if I decide to give it a run.
Tim
jimh posted 12-12-2009 12:54 PM ET (US)
A third problem with checking the ignition timing while running the engine with a test propeller at a dock: if done during mid-day and in strong sunlight, the engine timing light may have trouble illuminating the timing marks on the flywheel well enough to be seen clearly. Since the timing marks are on the top of the flywheel, they are typically in direct sunlight. This makes them harder to see than on your usual automotive timing indicator that is buried in the engine compartment and in deep shade. To overcome the problem, use a very powerful timing light and wait for evening.
Martino posted 12-12-2009 08:44 PM ET (US)
Going through this discussion on another site. Check out the Joe Reeves method. You do the WOT timing adjustment at cranking speed. He is a master OMC mechanic, assume he knows his stuff.
tedious posted 12-13-2009 08:22 AM ET (US)
Yes, the Joe Reeves method is what I was referring to in the posting above. But to repeat: On older OMCs, which this poster was asking about, unless you have reason to suspect the WOT timing is wrong, there's no reason to monkey with it. It will not change over time. If you do try to adjust the WOT timing, and get it wrong, you may well toast the motor in just a few minutes of running.
Tim
hank119 posted 12-13-2009 10:53 PM ET (US)
Jim,
I mark the the timing mark I want to see with white-out. Clearly visible in Florida sunlight.

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Author	Topic: Running Engine In the Water to Check Ignition Timing and Throttle Linkage Settings
gmoulder	posted 12-09-2009 11:17 AM ET (US) The Seloc manual that I have states many times that the boat must be in the water and under load to accurately check and set the timing and throttle linkage. The repair shop that works on the boat generally does good work, I think. They seem to be intelligent thoughtful guys who want to do a good job. The repair shop says that the Seloc people don't have it right, and that there is no need for in the water tuning. Being a mechanical engineer by trade, I generally trust written published procedures. What is going on here?
tedious	posted 12-09-2009 12:49 PM ET (US) I have found that the aftermarket manuals are generally not that great - OEM is best if you can find it. The OEM manual for that motor also says that you need to be in the water to set the idle speed correctly. However, your mechanics have probably learned through experience that in most cases, setting the idle speed somewhat higher on the muffs gives the right idle speed on the water. The other procedure that, per the manual, needs to be done on the water is setting the WOT timing, but there is a way to get that pretty close to correct while just cranking the motor. The bottom line is that if the mechanics are experienced with this very popular motor, I would trust them more than the aftermarket manual. The local mechanic I have spoken with, who has lots of experience with these motors, sets them up in the shop and then goes out for a water test. He indicates it's very rare that he has to make an on-the-water adjustment to get it right. Tim
gmoulder	posted 12-09-2009 05:09 PM ET (US) Tedious. Thanks, I feel better already about the efforts of repair shop. Would feel even better to have a knowledgable person tune it in the water. As for the repair manual, I have been needing some fire starter this winter.
brisboats	posted 12-09-2009 08:12 PM ET (US) The three cylinder loop charged engine has a large variance between idle speed in and out of water. It would be nice to say that the variance was a consistent 400 rpms for all engines but each engine is a little different so to get it perfect I would want the engine in the water. The WOT timing can be properly done in a test tank with a test wheel. It is very hard and dangerous to run a boat in open water at WOT with the cowl off and aim a timing light at the pointer all at the same time. Static timing the engine and a proper sync and link may get it right most times but not always. The shop that tunes out of water uses their customers for the water testing segment. Brian
modenacart	posted 12-09-2009 09:07 PM ET (US) I would think there would be variation depending on which hull the engine was on, thus making it very difficult for the OEM to set a limit for the idle speed outside of the water. I would do what the OEM says, usually the engineers are pretty smart and have a reason for why they recommend what they do.
jimh	posted 12-10-2009 09:47 AM ET (US) I have used a test wheel and checked my ignition timing while running my 225-HP two-cycle outboard engine at a dock. I discovered two important conditions which I had not anticipated: --running a 225-HP engine at near full throttle at a dock creates an enormous amount of noise, and --running a 225-HP engine at near full throttle at a dock creates an enormous amount of exhaust smoke. These two factors were unanticipated. My test drew a crowd of on-lookers to see if my engine was on fire or had gone into a runaway condition. After verifying the ignition time was within one degree of the recommended spark advance, I terminated the test. To check the ignition timing at full throttle you need an environment for the engine where it can run safely at high speed. Usually a test propeller or test wheel is used to create a load. Be prepared for a lot of noise and smoke.
Tom W Clark	posted 12-10-2009 10:23 AM ET (US) I would hesitate to pay money to an outboard mechanic that did not have a test tank and appropriate test wheels. Using one is standard operating procedure. My mechanic has three test tanks in his shop. Two of them are on wheels.
tedious	posted 12-10-2009 01:47 PM ET (US) Although doing things perfectly by the manual, including tank testing with a test wheel for WOT timing, would always be preferable, I suspect it's a rare mechanic that has test wheels available for whatever motor the customer comes in with. Tom, you seem to have found a good one, but it's a long commute... I would point out that the original object of this discussion, the vintage OMC 70 triple, is a fairly blunt instrument. Being off by a bit on the idle speed isn't going to make a whole lot of difference. And in practice, once WOT timing is set right, it shouldn't need adjustment - it's just a mechanical stop that limits the travel of the timer base, not something that is going to wear or go out of calibration. That may not be true for other motors. Good story about smoking up the dock, Jim - I did get at test wheel for my 70 (couldn't pass up deal on eBay) but I have not tried it yet. I will alert the fire department in advance if I decide to give it a run. Tim
jimh	posted 12-12-2009 12:54 PM ET (US) A third problem with checking the ignition timing while running the engine with a test propeller at a dock: if done during mid-day and in strong sunlight, the engine timing light may have trouble illuminating the timing marks on the flywheel well enough to be seen clearly. Since the timing marks are on the top of the flywheel, they are typically in direct sunlight. This makes them harder to see than on your usual automotive timing indicator that is buried in the engine compartment and in deep shade. To overcome the problem, use a very powerful timing light and wait for evening.
Martino	posted 12-12-2009 08:44 PM ET (US) Going through this discussion on another site. Check out the Joe Reeves method. You do the WOT timing adjustment at cranking speed. He is a master OMC mechanic, assume he knows his stuff.
tedious	posted 12-13-2009 08:22 AM ET (US) Yes, the Joe Reeves method is what I was referring to in the posting above. But to repeat: On older OMCs, which this poster was asking about, unless you have reason to suspect the WOT timing is wrong, there's no reason to monkey with it. It will not change over time. If you do try to adjust the WOT timing, and get it wrong, you may well toast the motor in just a few minutes of running. Tim
hank119	posted 12-13-2009 10:53 PM ET (US) Jim, I mark the the timing mark I want to see with white-out. Clearly visible in Florida sunlight.