Timing

I did a tune-up (cap, rotor, plugs, etc.) two summers ago and the boat has never idled quite as well since.

After setting/checking the timing and dwell and making sure the mixture screws on the carb are set properly, the boat still seems to idle rough. It won't cut off, but it just isn't as smooth and there is a vibration in the boat.

It seems like when I set the timing as far as 30 degs. it idles much smoother than at 10 degs. where I know it is supposed to be.

Does anybody have any ideas as to what would cause this phenomenon or what I should be looking for to get her dialed right in?

-Bud

I am wondering if its a bad wire too. It turns out the condenser in the tune-up kit was faulty so I guess it's not unrealistic that there could be a bad wire too.

I swear I have the order right, but it can't hurt to check again.

Thanks.

It runs perfectly fine once you get it above idle. Very smooth and strong out of the hole as it should be...

Also what plugs and plug gap are you running?

Please read through this thread for some ideas: http://www.mastercraft.com/teamtalk/showthread.php?t=42639&highlight=timing

An engine will idle better at 30 degrees, don't run it above idle though

Do you have one of the timing lights that can be set for bias? If so, it may need to be zero'd.

Bud,
Met you and your buddies couple years ago up at Buffalo's place on Lanier - I remember the issue with the condensor and everyone throwing their $0.02 at your boat that day. Why don't you set #1 to TDC and see where the timing mark is on the damper - this should help verify base timing. Don't know if you have degree tape on the damper that could be in the wrong location or maybe someone bent the pointer that is mounted on the block which would give incorrect info. As a side note I have a digital timing light your welcome to borrow and you can dial timing back to verify the setting. PM me if your interested - I work in Gwinnett and live in Cumming or meet somewhere along the hwy 20 corridor


Also if you set #1 to TDC you can then pull and reset distributor so the rotor is pointing to #1 plug wire.

If you actually have 30* initial and your distributor is advancing properly you'll destroy the thing from detonation. Shattered pistons and rings, hammered rod bearings, and all sorts of unpleasantry are in your future. You need to fix this before running the boat on the water under load, no exceptions.

Put a piston stop (either a real one, use a bolt, get creative with an old spark plug, whatever) in #1 and find TDC. To do this rotate engine by hand (socket and breaker bar on balancer bolt) until it hits the stop mark where the pointer is on the balancer. Then rotate the other way until it hits the stop and mark where it is on the balancer. Find the point directly between these marks and you have TDC. This should line up with the TDC mark on the balancer. If it does not, replace the balancer. It could be a bent timing pointer but they aren't going to be 20* off and you would know from looking at it if it's mangled enough to be more than a couple degrees off.

Fix this or you will destroy your engine either quickly from detonation or slowly from harmonics and a balancer that allows or encourages spaghetti crank. Either way it must be fixed or things will get expensive.

Well, by the time you notice detonation its way past where it actually starts to detonate timing wise. Thats why Pro Tec uses the knock sensor. It listens very closely to pre-detonation.

Go to youtube and see the difference between a motor that is too far advanced and when its not. Not much difference but big difference in the cylinders...

Well I checked everything out this morning and #1 tdc matches up to the tdc mark on the engine so that can be ruled out. I pulled the plug wire off each plug and did not notice a change in the engine when I pulled #5 and #8. Should you always notice a difference for every cylinder when a wire is pulled?

I also noticed that after I had idled the boat a while, shut it off for 10 min to check gap on all the plugs, and then turned it back on again, it actually ran quite smooth for about 30 seconds. After that is when it started to vibrate more. Could that indicate some kind of choke adjustment that should be made?

Yes, the boat should run noticeably worse when you pull any plug wire. Sounds like you either have 5 and 8 swapped, or something is preventing proper spark in those 2 cylinders. Check plugs, wires, cap and rotor.

Well, as an update, I had the boat out this weekend and I think I've got it as dialed in as it can be. Timing set @ 10*, idle mixture screws at peak vacuum setting, I adjusted the choke a little bit and that smoothed out the idle, though did make it a little crankier to start cold.

To clarify on the whole timing thing, it's not that it idled poorly at 10*, just not as well as when advanced to 20 or even 30, which as I've now learned from the other posts is to be expected.

So at this point she's idling in gear right at 600 RPM and pretty smooth. The whole issue with not noticing plugs pulled on 5 or 8 cyl. is strange to me, though. I know they're getting spark b/c it jolted me a couple times when pulling them off. I will swap in some new plugs and see if anything changes.

Thanks for all the help guys. I've learned a lot on this forum.

Will do, but geez that is frustrating. This is not a knock on SkiDIM b/c I think they're a great outfit, but that would mean both the condenser AND plug wires I bought from them have been bad.

The condenser gave me fits for a while as it was the very last item I swapped back to the old one since everyone I talked to said that couldn't be the issue because "those never go bad." As soon as the old went back in, engine ran great. Even Vince at DIM was surprised it was bad and to his credit he sent me a replacement for free. I didn't expect wires to be bad too, but what you've said makes perfect sense.

Couple ideas:

I assume you replaced your points when you did the tuneup in question. If yes, did the new points come with an extra metal strap/spring that the old ones didn't have? If yes, did you install it? Another thread mentioned issues when that is left out....although it was only a problem at high rpms. Worth checking anyway. It reminded me because that boat was also throwing stray sparks.

The only other thing I can think of is that the distributor itself is faulty. Not sure how it happens, or how to test(others on here might though). I've heard they can wear out and then wobble, not firing all cylinders.