Engine Noise at WOT

[achris]

Re: Engine Noise at WOT

Put the module in base timing mode. Adjust to 10 degrees BTDC. Remove ground wire and check that the timing is advancing as you increase the engine speed. You may have to adjust the idle speed screww on the carb as you retard the timing from 28 back to 10, as the engine speed will fall.

Yes the engine will appear to be very smooth and run well with the advance at 28. That could also account for the noises your hearing with the 19" prop on. The module is retarding the timing as much as it can, but with 28 it can't get it back far enough....

Get that initial timing back to 10 degress!!!

Chris..........

 

[Don S]

Re: Engine Noise at WOT

One other thing you might want to try.
Do a Compression Test.
I know you say it runs fine, but I have also had many customers tell me the same thing, only to hear it and know there is a problem.
Since we can't hear it run, we (I) need numbers.

Also, when trying to set the timing, you may have to adjust the idle speed up a bit to keep it running until you get a little closer to the proper timing and idle rpm.

 

[kwoolard]

Re: Engine Noise at WOT

Good, thanks!

Before I installed the freshwater cooling kit a couple of weeks ago, I meant to check the compression since I had the exhaust manifolds off, giving me easy access to the plugs. However, the compression tester that I have has a broken check valve and will not keep the highest pressure reading. It will just bounce the gauge up under compression.

I will try and get some universal spark plug sockets to make it easier to get them plugs out since I don't have but about 2-3 inches between my manifolds and the engine compartment.

Hopefully I can post back with some compression numbers in a few days. If I can't get to the plugs, I will just do the timing and idle speed adjustment. Its hard to believe my compression would be bad since the engine is fairly new and it starts with the first bump of the key and runs great.....however, like you say Don, I don't have that trained ear as you have.....this great sounding engine may sound completely different to you.

 

[kwoolard]

Re: Engine Noise at WOT

I haven't had a chance to get out and play with the timing or check compression due to the freezing weather we are having, but I wanted to throw a question out there.

If the timing at idle is 25 degrees, or anything too far advanced, would that cause incomplete combustion which it turn would cause the exhuast to smell rich? Just wondering if the rich exhuast at idle that I have, is related to the timing?

Thanks

 

[Coors]

Re: Engine Noise at WOT

I don't think it will start @25 degrees.
Either not getting base correct, or the hub has spun on the balancer.

 

[MikDee]

Re: Engine Noise at WOT

If your static timing is too far advanced, usually your engine will not crank well, it will, crank some then hesitate, again, & again, acting like it has a dead battery. Pinging, is detonation, just that,,, a hammering on your pistons, like a bomb about to go off, it's only a matter of time. Listen to Achris about setting your timing, and Get yourself a good comp. gauge, even Sears has one with a 2 piece hose on it to get into tight spaces, then check it, and let us know the results like Don says.

 

[kwoolard]

Re: Engine Noise at WOT

I didn't think it would start at 25 degrees either, but it does, and runs pretty well at idle and WOT. I've checked the base timing per the instructions in the manual, by grounding out the purple/white lead from the knock sensor. I have also checked TDC on the balancer and with the timing mark at zero, the piston is at the top of its stroke and the rotor points to the number 1 terminal under the cap.

I am going to fiddle with the timing once the weather warms up. What do you think about the previous question regarding timing and rich exhaust?

 

[Coors]

Re: Engine Noise at WOT

I don't think the engine can burn the fuel charge completely @25 degrees at 600 rpm. Something is lying to you about the timing, which could be dist not going into base, wrong connection or bad timing light, or spun hub.
When you say #1 is at tdc, or you using a gauge, or a piston stop?
Just being close to tdc can mean a big difference than being at actual tdc.
I don't know much about your ignition module, but at 28 degrees, the engine would be trying to have pistons forced backwards at times, and backfiring thru the carb.

 

[kwoolard]

Re: Engine Noise at WOT

I checked the TDC just using a straw stuck in the spark plug hole....I know a crude method, but it was the only thing I had on hand. I rotated the engine around twice checking it this way and both times got the timing mark at zero and the rotor on the #1 plug terminal.

I haven't checked the purple/white lead for a voltage supply while the engine was running, but I know it is the correct connection.

When I checked the timing in base mode the timing was solid at 25, and when I checked it out of base mode the timing was jumping around 28. So I believe the ICM is being locked into base mode.


If the ICM is not locked into base timing mode, would the ICM advance the timing that much at idle?

If the hub on the balancer was spun, would it give me consistent readings?

 

[FreeBeeTony]

Re: Engine Noise at WOT

How are you measuring the timing? What type of timing light do you have?
Are you really at 25*BTDC?

 

[kwoolard]

Re: Engine Noise at WOT

I am using a brand new craftsmen advanced timing light. I am grounding the purple white lead before starting the engine and since I couldn't see the timing marks I started rotating the dial on the back of the timing light. When I did that, the zero mark on the balancer moved towards the timing tab and I stopped when the zero mark on the balancer lined up with the timing tab, which was 25 degrees.

 

[MikDee]

Re: Engine Noise at WOT

I still think your static timing is out of whack. If the trigger in your distributor is not lined up with the rotor, (think about the high point of the cam for a breaker point distributor) meaning the trigger is firing, sending a spark to the rotor before it gets to terminal #1, it will show up as static advanced timing. Crazy as it sounds, I think you need to move all your spark plug wires back one terminal, (counterclockwise) so that when the trigger fires the spark to the rotor on cyl #1, it will be right on time, & show TDC,,, not 25* advanced. Then your engine will be firing correctly, no pinging, or excess gas smell, & your electronic spark advance will fall into line where it's supposed to be. You might have to advance your Dist. a bit (clockwise) to get it dead on. Somebody correct me if I'm wrong.

 

[kwoolard]

Re: Engine Noise at WOT

Mike,
I believe if I did that my timing would then be 20 degrees ATDC....so what is the difference in rotating the distributor now to retard the timing down 15 degrees to 10 BTDC or moving the plugs around and having to advance the timing 30 degrees to 10 BTDC?

 

[MikDee]

Re: Engine Noise at WOT

Ok, your Dist. is already in, so the rotor is already setup (if it were a breaker point Dist.) lets say it's just behind the high lobe of the Dist. cam, but lined up with terminal #1 on the cap, then on the next revolution, the points will break first (high lobe), the spark will fire before the rotor gets to #1, leaving it advanced, But you see, the rotor is directly on terminal #1! Hence if you set up your engine up manually to TDC #1 with a screwdriver, or whatever, then set your distributor this way, it will show advanced timing on a timing light that can read advance. Points or electronic Dist. it's gonna react the same.
__________________

 

[MikDee]

Re: Engine Noise at WOT

Ok, setup TDC of #1 on your crankshaft, take out the Dist. line up a point on the trigger (8pt. star wheel) with the pointer opposite it, while your rotor is pointing at #1 on your Dist cap, line it all up in synch, and then plant your distributor so it all lines up. You now know that when the trigger fires, it will go to the rotor, then terminal #1, to spark plug #1, at TDC. If the star wheel, and it's target point don't line up, you'll either be advanced or retarded.

 

[kwoolard]

Re: Engine Noise at WOT

This past weekend, I rechecked my timing, which was still at around 25 degrees base timing. I went to loosen the distributor and noticed that it didn't take much to loosen, so I think that it may have been possible for the distributor to rotate slightly under vibration. Anyway, I adjusted the base timing to 10 degrees and everything still seems to run fine. The rpms decreased about 150 rpms at idle when I made the adjustment, so I readjusted my idle rpm back to 650 and then readjusted the timing back to 10.

Hopefully, I can get back out on the water and check to make sure everything is advancing properly and see if the spark knock is gone.

The engine does seem to start a little easier now that the base timing is where it should be.

I talked with a couple of marine mechanics in the area about the timing on these motors and most had the response as "adjust the timing at 4000 rpms for 32 degrees total advance and let the initial fall where it does after the adjustment". It appears that these guys don't pay attention to the manual for checking the base timing on these TB V ignitions. This may be why my timing was off as well. To me it would seem hard to adjust the timing at high rpms since the ICM is making so many on the fly adjustments.

 

[Bondo]

Re: Engine Noise at WOT

I talked with a couple of marine mechanics in the area about the timing on these motors and most had the response as "adjust the timing at 4000 rpms for 32 degrees total advance and let the initial fall where it does after the adjustment". It appears that these guys don't pay attention to the manual for checking the base timing on these TB V ignitions. This may be why my timing was off as well. To me it would seem hard to adjust the timing at high rpms since the ICM is making so many on the fly adjustments.

Ayuh,.......

In the days Before electronic timing,.......

That Used to Work........

Todays motors are a different story........

 

[rotor_av8]

Re: Engine Noise at WOT

I'm no boat expert but know a fair amount about engines. It sounds to me like you are describing a valvetrain noise. This noise can be caused by early timing as well as loose valvetrain. If the valvetrain is loose it allows a tiny space between the rockers and pushrods when changing direction of motion. Too much space causes a tink tink or rattle sort of noise....like bb's like you said. It should usually do this under a load less but more at higher rpm's.

Adjust the timing then if it doesn't help get the valve lash checked out.

Before doing valve lash it might be easy enough to try different gas...unless this is a new issue on the same gas you always used. I have actually had detonation be audible a few times. I build a 11.5:1 compression ratio engine that would always rattle on low grade pump gas.

REMEMBER lower octane burns easier at a lower temp and less spark. Higher octane means it's harder to burn....this allows higher compression without combustion.

Pre-ignition...caused by hot spots or wrong/early timing...needs a spark or hot spot to IGNITE it...dirty heads or plugs will do it because the gunk stays hot

Detonation....caused by too much pressure and combusts...like a diesel...common from too low octane

-Rotor