Mer cruiser black scorpion no power and backfiring

[Ian-r]

Injectors booth cleaned and booth tested. Plugs fouled up totally so I replaced them.

 

[Fun Times]

They had played with the distributor and it was loose so I have reset it to no1 tdc with rotor in line with no 1 pin.

Since the distributor was turned!!! The type of distributor design you have makes this a little harder to get back into the correct spot without having the correct service manual for your engine model which is Mercruiser part number 90-864260001 or 90-864260T00 as a possible helpful guide due to you are between setting it the traditional way and the engine models that utilize a crank sensor like yours. The following link helps describes a better way of how to clock a distributor that uses a crank sensor.....< The problem is the info isn't exactly the same design distributor as you have but position is critical to have a good running engine... but it should help give you an idea of where to continue to ensure your distributor is set 100% correctly. http://forums.iboats.com/filedata/fetch?id=7001823 You may want to try turning the distributor while on the water/under load to see if you can get the engine to run better.

http://www.crankshaftcoalition.com/wiki/How_to_install_a_distributor
http://forums.iboats.com/forum/engi...mecruiser-5-0l-mpi-distibutor-proper-clocking
http://www.ebay.com/sch/i.html?_odk...X90-864260001.TRS0&_nkw=90-864260001&_sacat=0

 

[Ian-r]

I have all the service manuals 24 and 31. 24 is the closest to distributor and engine layout but none of them reference to tdc setup. From what I have seen with reference to the ecm555 you just set it to tdc on pin 1 and the ecm does the rest. Adjusting while running does nothing as the ecm needs the initial distributor reference on crank for initial timing. I have tried adjustment while running and it's does not appear to do anything until you rotate it past arc limit and then engine shuts down. There is a reference to adjustment if 1to 2 degrees past tdc centre and it should all fix everything, but I cannot see how this will cure the fault. I will give it a try and see anyway.

 

[alldodge]

This guy had the same issue
http://forums.iboats.com/forum/engi...ngines-outdrives/349548-black-scorpion-timing

 

[Ian-r]

Yep, I saw that one. I have set it up pretty much like that but still no good.

 

[Fun Times]

There is a reference to adjustment if 1to 2 degrees past tdc centre and it should all fix everything, but I cannot see how this will cure the fault. I will give it a try and see anyway.

At this point you've got to hope for the easiest stuff will resolve the issue...You may have tulip valves. After running the engine a few times, be sure to recheck a few of your new spark plugs to see if they are still getting fuel fouled.

Page 2 of the following service bulletin is a reason why I'd recommend turning the distributor a lot both ways to see if it seems to help any before going back to the original location if possible. Service Bulletin - Marine Mechanic

2. V8 engines only: If the performance of 1a and 1b (above) does not resolve the problem, bring the engine to TDC (firing). Remove the HVS distributor cap and verify that the rotor is pointing at the correct timing mark, 8, on the HVS housing between the 2 lines shown below. If this is correct, reinstall the HVS cap. Mark a reference line on the HVS distributor and intake manifold (so you know where the distributor was located after you move it in the following step). Loosen the distributor's clamping screw and rotate the distributor 1-2 degrees clockwise (viewed from top), then retighten the distributor's clamping screw. The engine should now run well. If it does not, then you can return it back to the original line that you marked before.

Also keep in mind that there's a variance in service manuals as far as the years go... so ensure the manuals appear to be the same with some of the eBay ones linked earlier. Be sure you can find the words Black Scorpion when looking up specifications. Much like Don mentioned in post # 6 of AD's link. You can't find the newer manuals online for free.

 

[Ian-r]

Had a look at the bulletins for the hvs cap, but mine is a hei cap and has no timing mark so I have to mark it up my self with a ruler. Am trying the 1-2 degree advance today and see how it goes.

 

[Ian-r]

Distributor position changed. Note to advance timing rotate dist anti clockwise not clockwise as in service bulletin. Still missing at around 4200rpm. Buying new dist cap and rotor.

 

[Ian-r]

Replaced distributor cap and rotor. Set to tdc and rotated about 2 degrees left. Load tested in the water all ok, no more backfiring and power loss. Went for a barefoot behind it this afternoon, all happy again.

 

[Rick Stephens]

Replaced distributor cap and rotor. Set to tdc and rotated about 2 degrees left. Load tested in the water all ok, no more backfiring and power loss. Went for a barefoot behind it this afternoon, all happy again.

Wow. Was just some little thing.

If you had taken to the dealer you would have paid out the nose and had a bunch of really expensive new parts installed. Bravo.

 

[Fun Times]

Replaced distributor cap and rotor. Set to tdc and rotated about 2 degrees left. Load tested in the water all ok, no more backfiring and power loss. Went for a barefoot behind it this afternoon, all happy again.

Had a small feeling it was going to be that. Just needed to find the right spot again. Glad you were able to get it running good and thanks for the update.:thumb:

Wow. Was just some little thing.

If you had taken to the dealer you would have paid out the nose and had a bunch of really expensive new parts installed. Bravo.

Yep I think you're correct Rick, especially since they were the ones that messed it up in the first place by turning the distributor assembly during service. They meant well I'm sure.:eagerness: