[apollard]

Ok, found what I needed in the link you posted. With Enable fixed/locked timing set to yes AND the value set to 10, adjust trigger angle until the marks line up just like the picture. IE, the 10* mark aligned with the notch on the block.

[apollard]

Some ideas on your tune:

Your VE table looks like a reasonable starting point, but I would turn off ‘Multiply VE value by MAP ratio’.

Make your Spark Table replicate mine. It mimics the factory timing. You can play with the timing at idle or midrange after the tune is set. Set cranking advance at 10. Turn off enable fixed timing if you haven’t already.

On the AFR table, I would start with 12.8 everywhere for safety. 12.5 maybe OK, but may be a little rich and complicate things. AFTER you get the VE table tuned you can lean out some areas like I was able to do. This is especially helpful in the idle and midrange areas.

Your idle is likely high because the idle air controller isn't hooked up and working. yet another thing to do, verify what type of IAC valve indmar used. A quick Google shows a stepper type, but is could be something different, MerCruiser used both stepper and PWM types.

[Izzy46]

Do you have CLT hooked up? Otherwise it is likely to default to 20*, and be permanently in warm up.

Yes, I've got the sensor hooked up. Today it started at around 30*C and went up to 50*C when I ran the engine for half a minute.

Here is a photo of the balancer and timing mark. You can just make out the reference point in the background.

IMG_20230319_173755_942.jpg (3.56 MiB) Viewed 693 times

As there are no other marks on the balancer I guess the one groove represents TDC. I will use the picture you posted from the manual above and move the timing forward from -30* to around -27*.

I will also change the settings as you suggested and report back. Unfortunately I'm on parent duty tonight so might be difficult to steal some time on the boat.

[PSIG]

If you are that far from your desired fixed timing of 10°BTC, then I would do a lot more than 3° change. Creep up on it in nibbles if you like, but if it is still running, march right to the 10°BTC fixed setting, and start tuning. If it responds poorly even with incremental adjustments, I would verify the timing mark is 0° actual, or something else. An occasional problem (Wrong timing mark, or wrong pointer position). Typically, a $10 piston stop tool through the spark plug hole is used to confirm 0°TDC.

[Izzy46]

If you are that far from your desired fixed timing of 10°BTC, then I would do a lot more than 3° change.

Sorry that was the best photo I could get. When the engine is running with the timing light it is much closer to the mark.

With Enable fixed/locked timing set to yes AND the value set to 10, adjust trigger angle until the marks line up just like the picture. IE, the 10* mark aligned with the notch on the block.

Screen Shot 2023-03-20 at 8.19.01 AM.png (52.2 KiB) Viewed 629 times

I set the value to 10 as above and the mark was already around 10* above the notch on the block. I would say that the timing looked pretty close to the picture you posted from the Indmar manual.
I then turned Locked timing off and proceeded with your other suggestions.

Your VE table looks like a reasonable starting point, but I would turn off ‘Multiply VE value by MAP ratio’.

This resulted in a much lower idle around 640. The idle was also not as smooth.

Make your Spark Table replicate mine. It mimics the factory timing. You can play with the timing at idle or midrange after the tune is set. Set cranking advance at 10. Turn off enable fixed timing if you haven’t already.

Slightly smoother idle oscillating between 580 and 620. I experimented with cranking advance at 10 and at 0, there didn’t seem to be any difference to starting.

On the AFR table, I would start with 12.8 everywhere for safety. 12.5 maybe OK, but may be a little rich and complicate things. AFTER you get the VE table tuned you can lean out some areas like I was able to do. This is especially helpful in the idle and midrange areas.

I made the changes without noticeable difference.

I had a bit of a play with the VE table in the range of 600 to 1200 rpm I went for values between your table and mine. Using the table below it now idles between 700 and 740. My understanding is that it should be around 800. Am I on the right track adjusting the VE table or should I also consider the spark table?

Your idle is likely high because the idle air controller isn't hooked up and working. yet another thing to do, verify what type of IAC valve indmar used. A quick Google shows a stepper type, but is could be something different, MerCruiser used both stepper and PWM types.

https://www.amazon.com/gp/product/B071S ... UTF8&psc=1
I have the throttle body above. This throttle body has 8 pins, my understanding is that 2 pins are to control the butterfly and then there 3 pins for each of the two potentiometers. I'm certain that the boat doesn't have an IAC valve.

Could it be possible that the idle is controlled by timing and fuel input alone?

Screen Shot 2023-03-20 at 9.25.35 AM.png (350.09 KiB) Viewed 627 times

[apollard]

Regarding the timing, GM made the EST distributor you have to run at 10* advance when setting timing (there is a lockout procedure, the one shown in the Indmar manual for carbureted engines). Since your balancer does not have other markings, it must be a GM balancer for the GM EFI cars. On those cars, the procedure is to lock out the timing and align the marks. This means the line on the GM balancer is at 10* advanced already.

Note that I can't find that on the web anywhere, but given the procedure GM igves for setting the timing and the stated 10* advance in the module, that must be correct.

So, one of these is true:
1 - your balncer's linne is at 10* already, and setting it 'around 10*' now has it at 20*, OR
2 - indmar changed the balancer and the line really is 0* (ie, TDC)

2 is possible but unlikely, because GM delivered complete long blocks to Mecruiser, Indmar, Volvo Penta, etc. I doubt Indmar would have changed anything since it would have voided any warranty claims. It's also possible GM installed a different balancer, but also not likely IMO.

In these two cases, assuming number 1 AND aligning the line and mark on the block is the safest since if the mark is in fact at TDC you would be running with lower timing. If it is at 10*, you would be exactly where you need to be.

If you leave it where it is (around 10* from the line), and number 2 is true, you are going to be running 10* more advance than you want. In a marine engine, this will result in detonation, and it will not be evident unless you are very good (and diligent) at looking for the clues. You cannot hear detonation in a marine engine at 2500 RPM and above. Lots of melted piston have proven that.

Safer still is getting a piston stop and verifying what you have (or another suitable method). If not I would run the safer option above.

Regarding the IAC, get the model # for your engine and use one of the sites that sells parts to see if there is an idle valve. I have not seen a MEFI system that did not have one. From you description, it sounds like you have electronic throttle, and it is possible they implemented idle control using that.

[PSIG]

Safer still is getting a piston stop and verifying what you have (or another suitable method).

100%, if you are not sure of where the mark is or what it means. Running hard at 10° effective retard is "safer", but still damaging. Extensive studies have shown the #1 cause of valve and valve seat damage is incorrect timing, forcing early rebuilds or repairs.

I have seen this repeatedly myself, on engines with malfunctioning advance mechanisms, and race distributors without vacuum advance used for cruising, or improperly tuned. Valves burn and seats recede. Sure, it will seem to run "OK" with incorrect timing. Either tune for best efficiency no matter what the numbers say, or get the numbers right.

[dazq]

That throttle you linked to looks definitely like a dbw body. Speeduino doesn't support that, you will need an external controller to run that body or you need to fit a std cable operated type
As has been suggested this is why you most likely wouldn't have an iac as dbw body's use the main butterfly to maintain the idle.

[apollard]

Before we get too far down the road, let's makes sure what we have.

Does your distributor look like the distributor with the flat cap and shielded terminals, or the tall one with exposed silver terminals (ie, HEI style)? If the flat style, that is for later MEFI (version 5 it seems) based computers. I cannot find published timing values for it, and do not have any experience with it.

Since your throttle is DBW, is your shift electronic? Because the factory computer likely handles those, and you will have to figure out how to do both. There are DBW DIY solutions, but I know of no DIY solution for electronic shift of boats. Perhaps the trans controller developed by those on this board can do it, but it would not be quick and easy. You'll need to consider how far down this rabbit hole you want to go, and if repairing the factory wiring is easier.

Not trying to discourage you, just factors to consider.

[Izzy46]

Sadly I didn't get time to work on the boat today but I did get a chance to call the local mechanic who knows the boat inside out. He rebuild the engine only two years ago and confirmed that the mark on the balancer when lined up with the notch is TDC. I understand this to mean that when piston one reaches the highest point the mark and the notch line up.

So, one of these is true:
1 - your balncer's linne is at 10* already, and setting it 'around 10*' now has it at 20*, OR
2 - indmar changed the balancer and the line really is 0* (ie, TDC)

Please forgive me as this is the first time I've timed an engine but the statement above has me a little puzzled... I think I need to go away and watch a few videos to get a better understanding of physical engine timing, the 10* advance in EST distributors and how computers further adjust timing.

In the meantime my take-away is that I need to set fixed/locked timing to yes AND set the value to 10, adjust trigger angle until the mark on the balancer lines up with the notch on the block? Is this assumption correct...?

In regard to your other questions:

My distributor is the second one in the picture.
https://www.amazon.com/gp/product/B0797 ... UTF8&psc=1

Since your throttle is DBW, is your shift electronic? Because the factory computer likely handles those, and you will have to figure out how to do both. There are DBW DIY solutions, but I know of no DIY solution for electronic shift of boats. Perhaps the trans controller developed by those on this board can do it, but it would not be quick and easy. You'll need to consider how far down this rabbit hole you want to go, and if repairing the factory wiring is easier.

Fortunately my transmission is cable controlled.

That throttle you linked to looks definitely like a dbw body. Speeduino doesn't support that, you will need an external controller to run that body or you need to fit a std cable operated type
As has been suggested this is why you most likely wouldn't have an iac as dbw body's use the main butterfly to maintain the idle.

To answer your question dazq my throttle is DBW and I'm using the DStage controller to run it.
https://github.com/DStageGarage/Electro ... l.docx.pdf