will 4deg of timing make a difference?

[Sea Ray Joe]

I have a 1992 18' Sea Ray with a 165hp 4.3.
My boat came originally with a 19 pitch prop. but will only turn a 17 pitch prop at proper rpm.
I just checked timing and it was at 4deg base. Factory setting is 8deg so I bumped it up.
Will this make a difference?
I need to buy a new prop before I go on holidays and would like to go back to a 19 pitch. I won't have a chance to try before I go.

Thanks
Joe.

 

[John_S]

Re: will 4deg of timing make a difference?

I have a 1992 18' Sea Ray with a 165hp 4.3.
My boat came originally with a 19 pitch prop. but will only turn a 17 pitch prop at proper rpm.
I just checked timing and it was at 4deg base. Factory setting is 8deg so I bumped it up.
Will this make a difference?
I need to buy a new prop before I go on holidays and would like to go back to a 19 pitch. I won't have a chance to try before I go.

Thanks
Joe.

Yes it will make a difference, but you will have to test with your 17" or 19" prop to see if it is "enough" of a difference, in your boat/load conditions. If you are at the top of your current wot range w/17", with a full load, than you might be able to go back to 19" with the correct timing.

 

[scca vette]

Re: will 4deg of timing make a difference?

Timing in a Chevy V8 (or V6) engine makes a big difference in how it runs and where the power is. A basic rule of thumb is if the timing is advanced it will have more low end (basically run stronger from a dead stop and lower RPM. If the timing is retarted it will run stronger in upper RPM range. This means at WOT and higher RPM it will run stronger. Timing being advanced will also help with fuel economy because the engine is running more efficient at normal operating RPM, basically the motor is not working as hard at a given RPM.

I am not sure about a boat motor (maybe somebody with more marine experience will advise) but with automotive engines I usually run them 2-4 degrees over the factory base setting. When the ESC is determined from the factory it is based on worse conditions (pulling a 10,000 lb trailer up a hill for example) and the vehicle still live so they are pretty conservative on the spark timing.

 

[JustJason]

Re: will 4deg of timing make a difference?

A basic rule of thumb is if the timing is advanced it will have more low end (basically run stronger from a dead stop and lower RPM. If the timing is retarted it will run stronger in upper RPM range. This means at WOT and higher RPM it will run stronger. Timing being advanced will also help with fuel economy because the engine is running more efficient at normal operating RPM, basically the motor is not working as hard at a given RPM.

None of that makes any sense.

Fuel burns at a constant rate. To compensate for that constate rate, you need to fire the plug off earlier (advance) the higher the rpm is. That's it, plain and simple.

If you don't fire the plug off earlier, you don't burn as much of the fuel, if you don't burn as much fuel, you don't make power. Plain and simple.

If you fire the plug to early (ie - over advanced) the engine hasn't compressed the mixture enough and some if it will burn via the plug, but the rest of it will self combust because of excessive cylinder pressure. When that happens you get 2 flame fronts expanding at the same time that overpressurizes and overheats the cylinder. This is called detonation and will tulip valves and melt holes in pistons... Nasty Stuff!

 

[Sea Ray Joe]

Re: will 4deg of timing make a difference?

I agree with Just Jason about how timing effects power output.
I was wondering about the amount of power I would be down with the timing retarded 4 degrees.

Also
When I checked for full advance with my dial back timing light I only saw 14 degrees of mechanical advance.
With my base of 8 this gives me 22 degrees total. Is this normal?
In a car I would expect between 30 and 36 degrees.

 

[John_S]

Re: will 4deg of timing make a difference?

When I checked for full advance with my dial back timing light I only saw 14 degrees of mechanical advance.
With my base of 8 this gives me 22 degrees total. Is this normal?
In a car I would expect between 30 and 36 degrees.

That would jive with Merc T4 modules for the early 90's V6 4.3L which only had 14 degrees of advance.

 

[JustJason]

Re: will 4deg of timing make a difference?

The older thunderfart 4 ignition systems don't have any knock protection either, so they are not as aggresive with the timing advance compared to a T5 or EST ignition system.

 

[scca vette]

Re: will 4deg of timing make a difference?

None of that makes any sense.

Fuel burns at a constant rate. To compensate for that constate rate, you need to fire the plug off earlier (advance) the higher the rpm is. That's it, plain and simple.

If you don't fire the plug off earlier, you don't burn as much of the fuel, if you don't burn as much fuel, you don't make power. Plain and simple.

If you fire the plug to early (ie - over advanced) the engine hasn't compressed the mixture enough and some if it will burn via the plug, but the rest of it will self combust because of excessive cylinder pressure. When that happens you get 2 flame fronts expanding at the same time that overpressurizes and overheats the cylinder. This is called detonation and will tulip valves and melt holes in pistons... Nasty Stuff!

Actually it is true, go to your local dragstrip and see how many people are running timing retard boxes and not on just boosted cars. The last time I dynoed my car we played with the timing a lot and even went as far as running 100 octane fuel to see how much initial advance we could get out of it. The dyno sheets shows the transfer of peak HP later in the RPM range with the timing retarted compared to it peaking earlier with the timing at its normal or advanced setting. With the timing retard it also widens the power peak across a larger RPM range before it starts to drop however it is in the upper RPM range (Example: Normal timing = 400 HP peak between 4900-5100 RPM. Timing Retard = 400 HP Peak between 5300 - 5600 RPM) I will try and dig up some old dyno sheets and you can see the difference in the profile of each run.

I agree 100% there is a limit on timing adv or ret and serious damage can come from this. I have owned a few turbo cars and know all about making this mistake. Most any stock small block GM can handle 2 to 4 degrees initial advance over factory settings with no problems. I spent some time at the GM proving grounds in Mesa AZ (before it was leveled and became condos) helping with some ESC calibrations on the GM 3800 and you would be amazed at what conditions vehicles have to be able to withstand. One day we had a dyne (trailer with electric motor that acts as if you are pulling any given weight) set to a 5K load, it was 105 degrees outside, we had the AC on full blast, using 86 octane fuel and was doing 1 mile WOT burst (stand still to 1 mile at full throttle) time and time again and there had to be 0 readings from the knock sensor.

Like I mentioned before I was gining by knowledge when it comes to building a car engine and may not 100% apply to marine application. I will be the first to admit that the more I get into redoing this boat the more I am learning myself.

 

[JustJason]

Re: will 4deg of timing make a difference?

Not to Dis you bro.... but the whole advance retard lingo doesn't fly.

With any piston engine, blown or not, nitro or not. You advance timing to compensate for the burn rate of fuel vs rpms.

Most engines do not start to advance timing until your at 1500 + - rpms. After that... you keep on advancing the timing until it knocks.
After it knocks, you dial it back 2 or 3 degrees if your a high performance guy and want all the power and not afraid to pay incase of a meltdown.
If your an average guy, stock motor guy, OEM manufactorer... you dial it back 4 or 5 degrees to give you a bit of a safety and reliability margin.

As far as the actual timing curve goes... that's up to either the engineer or whoever the backyardigan is to make full power at any rpm without having a bog from punching the throttle.

For example. If your at low rpm throttle, say 2000 rpms, and you punch the throttle, if the timing is not advanced enough at that point the engine will bog before it pushes through it and makes power.
Just the opposite, if the timing is advanced to far at 2k rpms, but your holding steady you will/should not knock. But if you punch it the motor will knock like crazey and push through it, or it will just knock. Either way will eventually damage the engine beyond repair.

Same idea goes for a corvette, indy car, boat motor, or weedwacker.

 

[bruceb58]

Re: will 4deg of timing make a difference?

Optimal spark advance is such that you have as much advance as you can get without pinging. That is what the knock sensors are for. Spark is advanced until the engine wants to ping and then is backed off.

When I worked at Delco we made some sensors for the Toyota racing team that actually measured cylinder pressure and we did signal processing on the pressure signature to detect the onset of ping. Each cylinder had its own sensor so each cylinder had its own individual advance correction. These sensors never made it into a production car because they were very expensive. They basically used a laser shining on a diaphragm.

I also worked at the GM proving grounds in AZ on various projects. Were you aware of why they were adjusting spark advance? It wasn't all for power. A lot is done for emission reasons.

Retarding the spark at higher RPM is nonsense if you want to increase power.

Now that we are way off topic, the OP should set his initial advance to spec and tweak depending on if he is getting ping under load. Of course conditions can change like age of fuel and load added to the boat so usually its best not to be on the hairy edge.

 

[Sea Ray Joe]

Re: will 4deg of timing make a difference?

Is it possible to run a module from a v8 on the v6 to get a little more mechanical advance without running to much base timing?

 

[jtmarten]

Re: will 4deg of timing make a difference?

I run mine to give 35-36* total timing.
No such thing as too much base timing (unless you go over 36*). Lots of performance boats run the dizzy locked (no advance) at 36*. The only issue is starting with full advance, so they run a switch for the coil feed. Crank it over, fire the coil, and you're off and running.

 

[John_S]

Re: will 4deg of timing make a difference?

Is it possible to run a module from a v8 on the v6 to get a little more mechanical advance without running to much base timing?

Way too much for your 4.3L. Running a V8 module on a V6 will give even more advance than what is stated on the module. Adjust your base timing to where it is suppose to be and run it. Leave the module alone.