1995 Evinrude 88-HP: Adjusting Engine Idle Speed

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Author Topic:   1995 Evinrude 88-HP: Adjusting Engine Idle Speed

hank119 posted 12-07-2009 12:34 AM ET (US)
I'm trying to set up my newly acquired rebuilt engine and remote control. I'm assuming that the WOT timing is correct since the rebuilder indicated it was done at the time of the rebuild. However, the lower engine speed setup was screwed up by an improper rigging of the engine with the new control on my boat at the builder's shop. I've launched the boat and it runs well at 3,000 to 4,000-RPM. The idle is terrible, however. I've been able to adjust the shifting; they screwed up at the engine connection as well as at the control. I'm left with the low speed adjustments.
The link and synch instructions in the Evinrude shop manual for this engine are confusing. I've adjusted the cam follower pickup so that it occurs when the throttle valves are both closed and the mark on the cam follower is simultaneously centered on the cam follower. As I understand it, the timing specification must be set at this pickup point. Adjusting the pickup timing is where I am running into trouble.
The manual tells me first to move the spark advance lever to adjust the timing to the specified value. On my engine there is also a thumb wheel adjustment between the main throttle lever and the throttle cam. The manual next says to adjust this thumb wheel to change the timing.
Can any one clarify this for me? Is there a simple technique for obtaining this adjustment.
jimh posted 12-07-2009 08:45 PM ET (US)
If you have the factory shop manual, you have the authoritative procedure for setting the idle speed.
In general, the goal of most two-cycle engine idle speed adjustments is to set the ignition timing to a particular point, set the throttle plate to closed, and align this with minimum throttle lever position or idle speed. This should produce the specified engine speed.
As the throttle level is moved forward, typically the ignition timing is advanced while the throttle plate stays closed. This results in increased engine speed.
Then, at some point the throttle plate begins to open, adding more engine speed. From this point of the throttle lever, both the ignition timing and throttle plate open with further movement of the throttle lever, producing increased engine speed. Finally, at some point the ignition timing stops advancing, and only the throttle plate continues to open.
hank119 posted 12-08-2009 01:31 AM ET (US)
Jimh, thanks for your comment.
It's true that the factory manual is the definitive procedure but my problem is that the instructions are ambiguous. The adjustment of the linkage on my engine to obtain the throttle opening/timing relationship you describe, are performed in the following sequence.
First make sure the throttle plates are closed and move simultaneously when manually actuated.
Second, with throttle plates closed, align an embossed mark on a throttle cam with the cam follower which moves the throttle plates. This establishes the pickup point at which the further movement of the throttle linkage causes the throttle to open.
Third check and adjust pickup timing. Ideally, checking the timing at this setting will result in the specified advance. However, if it doesn't fall within spec then set the timing to spec with the spark advance lever. Unfortunately, by moving the spark advance lever we displace the previously, carefully aligned cam and follower.
Fourth,(here's where it gets hazy). There is an adjusting rod which moves the aforementioned throttle cam independently from the spark advance lever. Instructions now say adjust timing with a thumb wheel adjustment of this rod. Moving this rod doesn't affect timing, just the throttle cam. Since we already have set the pickup timing in step three, it seems to me this adjustment should perhaps be used instead to realign the throttle cam embossed mark with the cam follower. Unless I'm missing something.
seahorse posted 12-08-2009 07:31 AM ET (US)
Since you have the cam pickup point and roller already adjusted, just advance the throttle up to that point and read the timing. If it's not where it should be, loosen the locknut and turn the thumbwheel to change the timing, and tighten the locknut. Reposition the throttle back to the cam pickup point and read the timing again. Adjust as needed.
tedious posted 12-08-2009 07:45 AM ET (US)
Hank, the thumbwheel basically adjusts the timing relative to the throttle cam. You change only the timing to adjust the idle speed - the carbs should stay completely closed.
With the throttle cam in the idle position (that's with the butterflies closed and the cam follower against the mark on the cam) you adjust the timing via the thumbwheel and locknut until you get the correct idle speed. There's no need to actually check the timing itself.

Note that the correct idle speed is supposed to be set only in the water, with the right prop, while moving. I set mine to about 1100 RPM on the muffs and it seems to come out OK in the water.
Tim
tedious posted 12-08-2009 07:49 AM ET (US)
Just one additional clarification, based on a more careful reading of your latest post: the rod, with the thumbwheel, connects the timer base to the throttle cam. Both timer base and throttle cam can move. What you are doing is holding the throttle cam still, in the idle position, and using the thumbwheel to move the timer base until you get the correct idle speed.
Tim
seahorse posted 12-08-2009 09:11 AM ET (US)

quote:

With the throttle cam in the idle position (that's with the butterflies closed and the cam follower against the mark on the cam) you adjust the timing via the thumbwheel and locknut until you get the correct idle speed. There's no need to actually check the timing itself.

That is incorrect advice, please read a service manual.
The thumbwheel adjusts the pick-up timing for proper midrange running.
Idle speed is a different adjustment.
tedious posted 12-08-2009 09:49 AM ET (US)
Sure you're not thinking about idle mixture, Seahorse? That is indeed a separate adjustment.
seahorse posted 12-08-2009 03:50 PM ET (US)
Sure you're not thinking about idle mixture, Seahorse? That is indeed a separate adjustment

there are no idle mixture adjustments on that motor -- fixed jets
A2J15Sport posted 12-08-2009 09:09 PM ET (US)
Seahorse is correct.
There are NO idle mixture adjustments. The idle speed IS a seperate adjustment from timing.
hank119 posted 12-09-2009 12:26 AM ET (US)
Thanks to all for your replies to my post.
Tedious, there are two thumb wheels on my engine.The upper one directly adjusts timing by moving a rod connected to the timer base. The other adjusts the position of the throttle cam relative to the carburetor and doesn't affect timing.
Seahorse, you seem to be suggesting that I adjust the timing with the upper thumb wheel. I had been avoiding this because I didn't want to change the length of the spark advance rod which I presume was set for WOT timing by the re-builder. My problem has been too much spark advance at the low speeds.This resulted in terrible idle.
What I have been doing to avoid upsetting WOT settings is to back out the idle stop and pull on the main throttle lever to reduce the spark advance as much as possible. This results in moving the throttle cam away from contact with the cam follower. I used the lower thumb wheel to move the cam back toward the cam follower. Then, if necessary, readjusted alignment of the cam roller to the mark on the cam. Then checked timing. Repeated when necessary.
I did this today and succeeded in barely getting the pickup timing in spec. Part of the difficulty was due to somewhat worn throttle cam and spark advance cam rollers.(I'm going to try to get new rollers.) I next had to make sure that I could preserve the minimum timing settings in connecting the throttle cable.
I was reasonably successful. My engine idles in gear at 600 to 650 rpm. A little low but reasonably smooth. It runs well up to 4000 rpm. I still haven't tried it at WOT.
seahorse posted 12-09-2009 11:16 PM ET (US)
hank119,
Your first post described your problem setting the pickup timing, not the full throttle timing which is adjusted by the (upper) thumbwheel on the long link from the throttle arm to the timer base.
To adjust the pickup timing, use the thumbwheel on the throttle cam.
Look at the plastic roller on the arm that opens the throttle plates to see if the outer coating is broken off. The #432639 roller should be at least 1/4" in diameter.
There is also a plastic coated roller inside the throttle linkage arc that attaches to the spark link lever. That roller is #432572 and it also breaks easily.
Replace both if you have any doubts as they affect the linkage geometry and proper timing.
tedious posted 12-10-2009 08:24 AM ET (US)
You're right, the upper thumbwheel adjusts the WOT timing, and you don't want to mess with it.
I think you're on the right track with your other adjustments, and your idle seems to be fine, so I think you're done. If you had the pickup timing wrong, you'd be having trouble when you throttle up.
When I got my 70, the roller on the cam follower was damaged - missing the outer cover. It was still possible to get it into the proper alignment, but only at the very end of the adjustment range. It sounds like you are in the same situation. I did replace the roller this fall, and it made it easier to get it right.
My bad on the idle mixture adjustment - some of these old OMCs have 'em, some don't.
Tim
64nauset posted 12-10-2009 10:56 AM ET (US)
Hello Hank. I have the same powerplant, 2 hours past break-in period, and I'm experiencing the same idle symptoms as you. It was installed new in '96 and never hit the water until last summer. Carbs cleaned of gum deposits, and ignition/compression checked by a crackerjack Evinrude mechanic. He thinks idle will work itself out after a bit of time on new plugs and 50:1 (25:1 for break-in). Before speaking with him about that I stupidly adjusted the timing pickup arm trying to get idle right, so now I will have to go back and re-do the setup come spring. I posted the procedure from the Clymer manual in case it sheds some different light on the subject. Files are big enough to print.
http://www.pbase.com/bmcelya/evinrude_88_idle_and_timing_sync
I don't know how to make a black link blue. Embarrassing. Lessons?
Note: 88 runs the Nauset mighty fast and smooth except at idle. Best of luck on yours. I have bookmarked this thread for light reading come spring..... bruce
hank119 posted 12-10-2009 11:40 PM ET (US)
Seahorse, thanks for the part numbers of the two cam rollers.
I shall try to get them and replace them. There is a lot of looseness in the linkage. Any internet sites where I can order them ?
64nauset, the Clymer manual is practically word for word the same as my 1995 Evinrude shop manual in describing link and synch.
Hank
seahorse posted 12-10-2009 11:45 PM ET (US)
www.shop.evinrude.com
Click on PARTS then scroll down to choose the year and model number
Mr T posted 12-11-2009 10:45 AM ET (US)
I know this is not what you might want to hear, but it would be worth it to have a mech set the carbs up once and leave it that way.
Carb synchronization on the motor is critical to keeping those motors alive. I've spoke with a couple guys about the issue and they all say the same thing.
hank119 posted 12-12-2009 11:50 PM ET (US)
Seahorse, thanks for the link to shop.evinrude.com. I've ordered both rollers and will replace them when they arrive.
Hopefully that will cure the excessive play in the linkage.
Mr.T, Thanks for your comment. The reason I'm adjusting the carburetor myself is because a mechanic did not do it properly. With the help of people on this messaage board I can do it better myself.

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Author	Topic: 1995 Evinrude 88-HP: Adjusting Engine Idle Speed
hank119	posted 12-07-2009 12:34 AM ET (US) I'm trying to set up my newly acquired rebuilt engine and remote control. I'm assuming that the WOT timing is correct since the rebuilder indicated it was done at the time of the rebuild. However, the lower engine speed setup was screwed up by an improper rigging of the engine with the new control on my boat at the builder's shop. I've launched the boat and it runs well at 3,000 to 4,000-RPM. The idle is terrible, however. I've been able to adjust the shifting; they screwed up at the engine connection as well as at the control. I'm left with the low speed adjustments. The link and synch instructions in the Evinrude shop manual for this engine are confusing. I've adjusted the cam follower pickup so that it occurs when the throttle valves are both closed and the mark on the cam follower is simultaneously centered on the cam follower. As I understand it, the timing specification must be set at this pickup point. Adjusting the pickup timing is where I am running into trouble. The manual tells me first to move the spark advance lever to adjust the timing to the specified value. On my engine there is also a thumb wheel adjustment between the main throttle lever and the throttle cam. The manual next says to adjust this thumb wheel to change the timing. Can any one clarify this for me? Is there a simple technique for obtaining this adjustment.
jimh	posted 12-07-2009 08:45 PM ET (US) If you have the factory shop manual, you have the authoritative procedure for setting the idle speed. In general, the goal of most two-cycle engine idle speed adjustments is to set the ignition timing to a particular point, set the throttle plate to closed, and align this with minimum throttle lever position or idle speed. This should produce the specified engine speed. As the throttle level is moved forward, typically the ignition timing is advanced while the throttle plate stays closed. This results in increased engine speed. Then, at some point the throttle plate begins to open, adding more engine speed. From this point of the throttle lever, both the ignition timing and throttle plate open with further movement of the throttle lever, producing increased engine speed. Finally, at some point the ignition timing stops advancing, and only the throttle plate continues to open.
hank119	posted 12-08-2009 01:31 AM ET (US) Jimh, thanks for your comment. It's true that the factory manual is the definitive procedure but my problem is that the instructions are ambiguous. The adjustment of the linkage on my engine to obtain the throttle opening/timing relationship you describe, are performed in the following sequence. First make sure the throttle plates are closed and move simultaneously when manually actuated. Second, with throttle plates closed, align an embossed mark on a throttle cam with the cam follower which moves the throttle plates. This establishes the pickup point at which the further movement of the throttle linkage causes the throttle to open. Third check and adjust pickup timing. Ideally, checking the timing at this setting will result in the specified advance. However, if it doesn't fall within spec then set the timing to spec with the spark advance lever. Unfortunately, by moving the spark advance lever we displace the previously, carefully aligned cam and follower. Fourth,(here's where it gets hazy). There is an adjusting rod which moves the aforementioned throttle cam independently from the spark advance lever. Instructions now say adjust timing with a thumb wheel adjustment of this rod. Moving this rod doesn't affect timing, just the throttle cam. Since we already have set the pickup timing in step three, it seems to me this adjustment should perhaps be used instead to realign the throttle cam embossed mark with the cam follower. Unless I'm missing something.
seahorse	posted 12-08-2009 07:31 AM ET (US) Since you have the cam pickup point and roller already adjusted, just advance the throttle up to that point and read the timing. If it's not where it should be, loosen the locknut and turn the thumbwheel to change the timing, and tighten the locknut. Reposition the throttle back to the cam pickup point and read the timing again. Adjust as needed.
tedious	posted 12-08-2009 07:45 AM ET (US) Hank, the thumbwheel basically adjusts the timing relative to the throttle cam. You change only the timing to adjust the idle speed - the carbs should stay completely closed. With the throttle cam in the idle position (that's with the butterflies closed and the cam follower against the mark on the cam) you adjust the timing via the thumbwheel and locknut until you get the correct idle speed. There's no need to actually check the timing itself. Note that the correct idle speed is supposed to be set only in the water, with the right prop, while moving. I set mine to about 1100 RPM on the muffs and it seems to come out OK in the water. Tim
tedious	posted 12-08-2009 07:49 AM ET (US) Just one additional clarification, based on a more careful reading of your latest post: the rod, with the thumbwheel, connects the timer base to the throttle cam. Both timer base and throttle cam can move. What you are doing is holding the throttle cam still, in the idle position, and using the thumbwheel to move the timer base until you get the correct idle speed. Tim
seahorse	posted 12-08-2009 09:11 AM ET (US) quote: With the throttle cam in the idle position (that's with the butterflies closed and the cam follower against the mark on the cam) you adjust the timing via the thumbwheel and locknut until you get the correct idle speed. There's no need to actually check the timing itself. That is incorrect advice, please read a service manual. The thumbwheel adjusts the pick-up timing for proper midrange running. Idle speed is a different adjustment.
tedious	posted 12-08-2009 09:49 AM ET (US) Sure you're not thinking about idle mixture, Seahorse? That is indeed a separate adjustment.
seahorse	posted 12-08-2009 03:50 PM ET (US) Sure you're not thinking about idle mixture, Seahorse? That is indeed a separate adjustment there are no idle mixture adjustments on that motor -- fixed jets
A2J15Sport	posted 12-08-2009 09:09 PM ET (US) Seahorse is correct. There are NO idle mixture adjustments. The idle speed IS a seperate adjustment from timing.
hank119	posted 12-09-2009 12:26 AM ET (US) Thanks to all for your replies to my post. Tedious, there are two thumb wheels on my engine.The upper one directly adjusts timing by moving a rod connected to the timer base. The other adjusts the position of the throttle cam relative to the carburetor and doesn't affect timing. Seahorse, you seem to be suggesting that I adjust the timing with the upper thumb wheel. I had been avoiding this because I didn't want to change the length of the spark advance rod which I presume was set for WOT timing by the re-builder. My problem has been too much spark advance at the low speeds.This resulted in terrible idle. What I have been doing to avoid upsetting WOT settings is to back out the idle stop and pull on the main throttle lever to reduce the spark advance as much as possible. This results in moving the throttle cam away from contact with the cam follower. I used the lower thumb wheel to move the cam back toward the cam follower. Then, if necessary, readjusted alignment of the cam roller to the mark on the cam. Then checked timing. Repeated when necessary. I did this today and succeeded in barely getting the pickup timing in spec. Part of the difficulty was due to somewhat worn throttle cam and spark advance cam rollers.(I'm going to try to get new rollers.) I next had to make sure that I could preserve the minimum timing settings in connecting the throttle cable. I was reasonably successful. My engine idles in gear at 600 to 650 rpm. A little low but reasonably smooth. It runs well up to 4000 rpm. I still haven't tried it at WOT.
seahorse	posted 12-09-2009 11:16 PM ET (US) hank119, Your first post described your problem setting the pickup timing, not the full throttle timing which is adjusted by the (upper) thumbwheel on the long link from the throttle arm to the timer base. To adjust the pickup timing, use the thumbwheel on the throttle cam. Look at the plastic roller on the arm that opens the throttle plates to see if the outer coating is broken off. The #432639 roller should be at least 1/4" in diameter. There is also a plastic coated roller inside the throttle linkage arc that attaches to the spark link lever. That roller is #432572 and it also breaks easily. Replace both if you have any doubts as they affect the linkage geometry and proper timing.
tedious	posted 12-10-2009 08:24 AM ET (US) You're right, the upper thumbwheel adjusts the WOT timing, and you don't want to mess with it. I think you're on the right track with your other adjustments, and your idle seems to be fine, so I think you're done. If you had the pickup timing wrong, you'd be having trouble when you throttle up. When I got my 70, the roller on the cam follower was damaged - missing the outer cover. It was still possible to get it into the proper alignment, but only at the very end of the adjustment range. It sounds like you are in the same situation. I did replace the roller this fall, and it made it easier to get it right. My bad on the idle mixture adjustment - some of these old OMCs have 'em, some don't. Tim
64nauset	posted 12-10-2009 10:56 AM ET (US) Hello Hank. I have the same powerplant, 2 hours past break-in period, and I'm experiencing the same idle symptoms as you. It was installed new in '96 and never hit the water until last summer. Carbs cleaned of gum deposits, and ignition/compression checked by a crackerjack Evinrude mechanic. He thinks idle will work itself out after a bit of time on new plugs and 50:1 (25:1 for break-in). Before speaking with him about that I stupidly adjusted the timing pickup arm trying to get idle right, so now I will have to go back and re-do the setup come spring. I posted the procedure from the Clymer manual in case it sheds some different light on the subject. Files are big enough to print. http://www.pbase.com/bmcelya/evinrude_88_idle_and_timing_sync I don't know how to make a black link blue. Embarrassing. Lessons? Note: 88 runs the Nauset mighty fast and smooth except at idle. Best of luck on yours. I have bookmarked this thread for light reading come spring..... bruce
hank119	posted 12-10-2009 11:40 PM ET (US) Seahorse, thanks for the part numbers of the two cam rollers. I shall try to get them and replace them. There is a lot of looseness in the linkage. Any internet sites where I can order them ? 64nauset, the Clymer manual is practically word for word the same as my 1995 Evinrude shop manual in describing link and synch. Hank
seahorse	posted 12-10-2009 11:45 PM ET (US) www.shop.evinrude.com Click on PARTS then scroll down to choose the year and model number
Mr T	posted 12-11-2009 10:45 AM ET (US) I know this is not what you might want to hear, but it would be worth it to have a mech set the carbs up once and leave it that way. Carb synchronization on the motor is critical to keeping those motors alive. I've spoke with a couple guys about the issue and they all say the same thing.
hank119	posted 12-12-2009 11:50 PM ET (US) Seahorse, thanks for the link to shop.evinrude.com. I've ordered both rollers and will replace them when they arrive. Hopefully that will cure the excessive play in the linkage. Mr.T, Thanks for your comment. The reason I'm adjusting the carburetor myself is because a mechanic did not do it properly. With the help of people on this messaage board I can do it better myself.