84' 140 - Transistional Hesistation Problem

[hoeser]

Hi Guys,

I was hoping you could lend some insight on an issue I've been experiencing pretty much "forever" with my 1984 Evinrude 140 crossflow. I rebuilt the powerhead 2 years ago and installed all new pistons into freshly machined cylinders, the compression is an even 120 on all banks as of a few weeks ago. For as long as I can remember this engine has had this transitional hesitation when putting the hammer down from idle or low speed running to full throttle. The engine runs fine through the entire band but when you quickly advance the throttle it shudders a bit until it "clears its throat" and then you feel the torque come in like a wave of power.

If you are running high rpm and then come back down to idle for a second and reapply full throttle, it usually will not hesitate at all, it will just advance smoothly. If you spend more than a few moments in the low speeds, when you re-advance the throttle to full it will hesitate on the transition.

Hopefully the details here are clear enough to get some ideas. It almost feels like its loading a bit (?)

Thanks in advance!

 

[Dhadley]

Re: 84' 140 - Transistional Hesistation Problem

Could be loading up, sure. What spark plugs are you running? What's the total timing set at?

 

[hoeser]

Re: 84' 140 - Transistional Hesistation Problem

I'm running QL77JC4's gapped at 40 but I've had them at 35 and 45 as well, I tend to keep the gap a little narrower than spec as it seems to improve idle speed running (even though it shaves a bit off the top end). In any case, the gap has never effected that hesitation I'm talking about.

The timing is set to whatever is written on the breather box cover, I can't remember now it's been a while, I want to say 28 degrees at WOT though? Or does that sound ridiculous?

I'm curious, if the timing isn't set correctly, will that cause the hesitation to happen sometimes and not other times (ie: idle around for a bit, hammer down, it happens, idle around for a few seconds after being WOT, hammer down, it doesn't happen)?

 

[Dhadley]

Re: 84' 140 - Transistional Hesistation Problem

OK, good choice on plugs and 28 is correct for the timing. You could double check the sync-n-link. Maybe allow a little more timing advance before the cam follower picks up the carb roller. We'll assume that you've checked the carb jets to make sure they are all the correct ones. We'll further assume that the wot rpm is somewhere close to 5800 with an average load. Plus we'll assume that you're using fresh 87 octane.

 

[hoeser]

Re: 84' 140 - Transistional Hesistation Problem

Wide open is almost exactly 5800rpm in warm water and close to 6000 in colder temperatures. Fresh 87 octane, TCW-3 with a shiny-new-last-year VRO injection system (by the way the hesitation happened before and after the pump change).

I wouldn't mind a reference to a GOOD sink-n'-link procedure, I have a shop manual but it's not OEM and it really doesn't do a good job on the description of how to do it properly. I use the Joe Reeve's method on setting the timing (cranking at WOT with a spark tester and setting it to 24 degrees).

 

[Dhadley]

Re: 84' 140 - Transistional Hesistation Problem

The sync-n-link proceedure is pretty simple but the pics in the OE manual really help. Basically you just make sure the carb butterflies are closed at idle and make sure the cam follower doesn't pick up throttle until the line on it hits the roller as the throttle is advanced.

 

[hoeser]

Re: 84' 140 - Transistional Hesistation Problem

As I visualize that in my head it sounds pretty simple. Firstly, the carbs are linked together accurately, I know that for sure. The butterflys are snyc'd between the two carbs. I also know that the timing is advanced "somewhat" before it picks up the throttle roller, I don't know how much or where it should be picking it up, that's the only piece that is missing in my head. You're saying maybe try having it advance "more" before it picks up the roller? How much more is the real question. I'm also going to redo the WOT timing before I start this procedure as its been a while, hell, maybe its off.

 

[Dhadley]

Re: 84' 140 - Transistional Hesistation Problem

Start by looking at the cam follower and it's relation to the roller. Maybe it's picking up the carbs too soon now. As the linkage is moved by the throttle the timing will advance a bit before the cam follower hits the roller. The cam follower should start to move the roller as the line on the roller gets even with the roller.

 

[hoeser]

Re: 84' 140 - Transistional Hesistation Problem

Thanks for all your help Dhadley it's been quite informative. This may be a stupid question but where would be the best point in the linkage/roller system to adjust this without affecting the WOT timing? Seems to me the screw/nut holding the roller on the plate?

 

[Dhadley]

Re: 84' 140 - Transistional Hesistation Problem

Yes, moving the roller has no affect on wot timing. That only affects when the carbs start to open. If it's way off it may not allow the carbs to open completely. Or if it's way off the other direction it may open the butterflies past center (only on some carbs).

 

[hoeser]

Re: 84' 140 - Transistional Hesistation Problem

Would it be logical to assume in either case no damage can really be done to the engine?

 

[Dhadley]

Re: 84' 140 - Transistional Hesistation Problem

Shouldn't cause any damage - just the aggrivation. There may be a couple other things to look at but we need to start with the basics. Once we have a baseline and know everything is OK if it still acts funny then we'll look elsewhere. I like to do the simple stuff first.