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2008 monsoon 340 repower


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Sunscaper

What's up crew!!!

Need some advice from some of you gear heads.  Found a cracked block after winter storms.  Every mechanic I talked too was 6 weeks out, so I decided to just buy a new long block and install it my self.  It was time consuming but not a terrible job.  New motor is back together and in the boat.  First start was a little stiff but eventually fired and seemed to idle normal.  I then scheduled to take to local Malibu dealership here in Houston for them to set the timing for me.  Here is where I need your help.  They claim that the timing will not adjust.  So I am not sure where the problem could be.  I have removed timing cover and checked that timing chain is correct.  Distributor points at #1 at top dead center. Could the ecm be in some sort of limp mode that is not allowing timing to adjust?  Is the distributor off a gear?

Started again on hose yesterday, and I see what they are talking about, when you turn distributor there is no change in engine.  If you turn either way very far it just dies.

Any help would be great

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39 minutes ago, Sunscaper said:

What's up crew!!!

Need some advice from some of you gear heads.  Found a cracked block after winter storms.  Every mechanic I talked too was 6 weeks out, so I decided to just buy a new long block and install it my self.  It was time consuming but not a terrible job.  New motor is back together and in the boat.  First start was a little stiff but eventually fired and seemed to idle normal.  I then scheduled to take to local Malibu dealership here in Houston for them to set the timing for me.  Here is where I need your help.  They claim that the timing will not adjust.  So I am not sure where the problem could be.  I have removed timing cover and checked that timing chain is correct.  Distributor points at #1 at top dead center. Could the ecm be in some sort of limp mode that is not allowing timing to adjust?  Is the distributor off a gear?

Started again on hose yesterday, and I see what they are talking about, when you turn distributor there is no change in engine.  If you turn either way very far it just dies.

Any help would be great

Download the MEFI ECM service manual for your version of MEFI controller.  I'm guessing it is MEFI 5.  It will tell you how to jumper the ECM into service mode and set the base timing (which I'm guessing is 10* BTDC).  Your dealer knows this....

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When installing the HVS (high voltage switch / distributor) the engine should be at TDC compression stroke on cylinder 1.  Align the detent mark below the gear with the paint mark above the gear on the bottom of the HVS, line up the slot in the oil pump shaft using a long standard screwdriver, and install the HVS with the flat part of the HVS housing facing the front of the engine.

After the HVS is installed, turn the housing so the rotor is aligned with the little pointer in the housing stamped with the number 8.  If it won't line up then the HVS and cam gear may be a tooth off and it will need to be removed, turn the shaft a little, and reinstall it.  Once the rotor is aligned properly, tighten the hold down clamp and install the cap and wiring.

With the engine running at 1200 RPM, use Diacom to check the cam angle.  It should be at 705 +- 5 degrees (so, 700 to 710 degrees).  Loosen the hold down clamp and turn the HVS if needed to get the correct cam angle adjustment, then tighten the clamp again.

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3 hours ago, csleaver said:

When installing the HVS (high voltage switch / distributor) the engine should be at TDC compression stroke on cylinder 1.  Align the detent mark below the gear with the paint mark above the gear on the bottom of the HVS, line up the slot in the oil pump shaft using a long standard screwdriver, and install the HVS with the flat part of the HVS housing facing the front of the engine.

After the HVS is installed, turn the housing so the rotor is aligned with the little pointer in the housing stamped with the number 8.  If it won't line up then the HVS and cam gear may be a tooth off and it will need to be removed, turn the shaft a little, and reinstall it.  Once the rotor is aligned properly, tighten the hold down clamp and install the cap and wiring.

With the engine running at 1200 RPM, use Diacom to check the cam angle.  It should be at 705 +- 5 degrees (so, 700 to 710 degrees).  Loosen the hold down clamp and turn the HVS if needed to get the correct cam angle adjustment, then tighten the clamp again.

Almost the same as 10* BTDC...  thanks for filling in the details. 

@Sunscaper's dealer should have told him, or at least just performed the service for him.

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It is kind of similar, but Volvo Penta and Mercruiser used a very similar HVS ignition setup on the 5.7 GM, but the hold down is slotted so the cam angle is preset with no adjustment.  Once I did have to modify a Volvo v6 hold down to adjust the HVS so the engine would run properly.

The crank position reluctor on the 5.7 only has 4 poles, so it needs input from the cam position in the HVS to determine where the rotor is pointing and then the MEFI5 ECM knows when to use one of its coil drivers to signal the external ignition module to open the primary coil circuit and make spark at the right time.  Many GM Gen III or IV engines use a crank and/or cam sensor integrated into the engine block and a 24 or 58 pole reluctor on the crankshaft for ECM ignition timing input and 8 coil drivers to control the CNP coils.

Timing can be set more easily on older carbureted boats at idle speed because the coil is controlled by breaker points (or a very simple ignition module and sensor) and the ignition advance was just controlled by weights, springs, and centrifugal force.

Most MEFI 1-4 and many carbureted boats that don't have a crank position sensor use the Delphi distributer that has an ignition module, pickup coil, and sensor to determine when to open the primary coil circuit.  The module reads engine RPM and constantly controls the ignition advance to regulate it, so the advance must be turned off to correctly set the initial ignition timing on the engine, hence the need for a timing mode.

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Sunscaper

I appreciate all you guys info.  I am still working on this.  It doesn't make since to me why Malibu dealer cant get this to move.   I understand that the computer will adjust for any movement in distributor, but when they have it hooked to Diacom, it should change.  Im going to pull distributor again and double check that is in the correct position.  My biggest concern is that the ecm is not talking to diacom properly to let it change.  I do have MEFI 5 ecm and cam angle should be set to 705, I think it 630 when they hooked to computer.  But they could only get it to move like 15 degrees either way.  Maybe distributor is a tooth off.  But seems to run very good for it to be off that much.

Any one know where to find info on jumpering the mefi 5 into base mode

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You don't need a jumper shunt to set the cam angle on engines with the MEFI 5 and HVS, you just need Diacom to read the cam angle and the engine running at about 1200 to 1600 RPM so you know when the cam angle is adjusted correctly. 

If the cam angle can not be adjusted to 700-710 degrees it is very likely that the HVS is a tooth off.  There is a very limited amount of adjustment on Malibu boats (and many Supra/Moomba boats) due to the design of the intake plenum.

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