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454 MPI advance timing issue

Old 08-24-2020, 12:38 PM
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Default 454 MPI advance timing issue

I have a 1999 baja outlaw 25 with a 7.4 MPI and I'm not getting advance timing... I have checked the base timing in service mode and it is at 8 deg. I took the boat out yesterday and had my friend drive the boat at 3000 rpm and I was only showing about 15 deg on the timing gun. I have tried a new ignition module and it does the same as the stock module. I am currently at 4100 rpm WOT running a 21p 3 blade prop. I just did a tune up and put new plugs, cap, wires, FPR, pulled and cleaned/serviced fuel injectors. I've never had the boat running right since I bought it and now it's close but I'm missing some timing up top. Any suggestions? Is it ok to clock the distributor to get more timing? Or is it critical to stay at the 8 deb base timing per the mercruiser recommendation? j

Could it be the knock sensors retarding the timing? I did put a new knock sensor on the port side, but didn't replace the starboard side.
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Old 08-24-2020, 12:48 PM
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All knock sensors are not created equal, are they the correct ones for your engine ? the timing needs to stay @ 8* and let the ecm do the rest, Id verify TDC on the balancer with #1 on compression stroke, dont rule out fuel pressure, where is it ?

Are you sure its out of BT mode
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Old 08-24-2020, 01:12 PM
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yes the knock sensor was specifically for my engine. Fuel pressure at the rail is about mid 40's. I'll have to check TDC again. It shouldn't be in BT mode since I jumped the A and B terminals with a paper clip. Once I pull the clip it should go back to regular mode right?
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Old 08-24-2020, 01:28 PM
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Originally Posted by jevonlau View Post
yes the knock sensor was specifically for my engine. Fuel pressure at the rail is about mid 40's. I'll have to check TDC again. It shouldn't be in BT mode since I jumped the A and B terminals with a paper clip. Once I pull the clip it should go back to regular mode right?
have no idea I use a scanner
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Old 08-24-2020, 01:54 PM
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Originally Posted by jevonlau View Post
yes the knock sensor was specifically for my engine. Fuel pressure at the rail is about mid 40's. I'll have to check TDC again. It shouldn't be in BT mode since I jumped the A and B terminals with a paper clip. Once I pull the clip it should go back to regular mode right?
Yes once you pull the clip it will return to regular timing mode.
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Old 08-24-2020, 09:48 PM
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Originally Posted by F-2 Speedy View Post
All knock sensors are not created equal, are they the correct ones for your engine ? the timing needs to stay @ 8* and let the ecm do the rest, Id verify TDC on the balancer with #1 on compression stroke, dont rule out fuel pressure, where is it ?

Are you sure its out of BT mode

I checked TDC on plug 1 and the line on the balancer matches the pointer and the piston is at the top when I pulled the plug and checked. I pulled the cap and checked the rotor and the plastic tab is pointing to where the plug 1 wire is (between 5 and 6 oclock). Is the plastic tab supposed to point to 1? Or is the opposite end with the metal contact supposed to point to 1? I would think it wouldn't even start and run if the rotor was 180 deg off (if the metal contact part is supposed to point to 1) . Here's a pic of the rotor at TDC


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Old 08-24-2020, 09:56 PM
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where the metal contact is pointing now is to the wire for plug #6, which is 180deg from #1. Engine runs and idles great, just not getting advance timing so I am confused! lol
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Old 08-24-2020, 09:57 PM
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How do we know if the advance you saw isnít correct for the throttle position/intake vacuum/coolant temp/ and rpm ?

Anyone know the tables ? Articfriends/sutphen30/others here that have programmed the ecuís for these motors want to speak up ?
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Old 08-24-2020, 11:06 PM
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Originally Posted by jevonlau View Post
where the metal contact is pointing now is to the wire for plug #6, which is 180deg from #1. Engine runs and idles great, just not getting advance timing so I am confused! lol
Looks like you're at TDC but on the exhaust stroke.
Turn the crankshaft 360 degs (in the normal direction) and check the rotor again. It will be pointing right at the #1 wire. The dist turns once for every 2 turns of the crankshaft.

It would be nice if you could get scanner connected while under way and see what the sensors are reporting.
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Old 08-24-2020, 11:23 PM
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Originally Posted by SB View Post
How do we know if the advance you saw isnít correct for the throttle position/intake vacuum/coolant temp/ and rpm ?

Anyone know the tables ? Articfriends/sutphen30/others here that have programmed the ecuís for these motors want to speak up ?
You bring up a very valid point....but....I have not viewed the spark map for this particular motor but most Merc tables I have on hand would have more than 15 deg of timing at his stated rpm.

It is possible that knock retard is in affect but max retard is typically about 9 degrees, so he would still be shy in the timing department if it was pulling timing to the max.

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