No Spark - 1995 5.7 Bravo ENG: 0F287508 457B110HS Thunderbolt V

[rocklydockly]

I'm in a no-start situation. No spark, coil looked bad (oil leaked out the top, maybe, no audible oil in coil) put in new coil, Found very loose ground coming off of the ignition modules mounted behind distributor, black ground wire was on the metal mount for these modules, tightened it up, was sure I'd be good to go. No spark based on looking for spark from coil wire to through hull transom bolt 1/2 inch gap.

Ohms on primary coil terminals (+ and - ) = .8 , From plus to high voltage is very high on ohm meter.

I'm unsure of wiring to coil. All I can find online are Thunderbolt IV diagrams. I have two gray wires and the white Hobbs Meter (Hours) going to the minus side and I have one purple wire going to the plus side. It seems there should be another wire on the plus side, If so, I don't see it.

Advice and links to Thunderbolt V diagrams appreciated.

 

[alldodge]

I'm in a no-start situation. No spark, coil looked bad (oil leaked out the top, maybe, no audible oil in coil) put in new coil, Found very loose ground coming off of the ignition modules mounted behind distributor, black ground wire was on the metal mount for these modules, tightened it up, was sure I'd be good to go. No spark based on looking for spark from coil wire to through hull transom bolt 1/2 inch gap.

Ohms on primary coil terminals (+ and - ) = .8 , From plus to high voltage is very high on ohm meter.

I'm unsure of wiring to coil. All I can find online are Thunderbolt IV diagrams. I have two gray wires and the white Hobbs Meter (Hours) going to the minus side and I have one purple wire going to the plus side. It seems there should be another wire on the plus side, If so, I don't see it.

Advice and links to Thunderbolt V diagrams appreciated.

Hey we both have the same boat, mine just has the 7.4L. You should have one purple on the + side and gray wire on the - side. One gray goes to your tach and the other goes to you distributer. Remove the white wire going to the hobs meter, if it needs a ground use the engine block not the - side of the coil. If your tach went bad the gray wire going to the coil can stop your spark. Here is the troubleshooting guide

 

[rocklydockly]

Thanks, I wasn't able to see the pix, but I did find the manuals online at http://boatinfo.no/lib/library.html . It took a while to figure out which one was for my boat- #17. I went through the ignition troubleshooting and it turned out to be my sensor assembly in the distributor. Will replace ASAP and hopefully be on the water.

 

[rocklydockly]

Replaced the sensor with a Mallory part. Had an extra wire for ground. Installed and boat started on the second try. Probably a little fuel starved on first try. Grounded the purple wire that has a rubber plug to set in base timing mode. Used my new timing light. Idle was quite rough and timing looked like it was all over the place. Will try again in the daylight. Not an expert with timing light, but have the general sense of things.

Rotor is a tight fit on the distributor shaft, manual recommends loctite and a night upside down. That seems like overkill. Even with the tight fit, their is a minute amount of mechanical play. not sure if it's rotor to shaft or the gears on the end of the shaft. Any comments would be appreciated. Thanks.

 

[Bondo]

Replaced the sensor with a Mallory part. Had an extra wire for ground. Installed and boat started on the second try. Probably a little fuel starved on first try. Grounded the purple wire that has a rubber plug to set in base timing mode. Used my new timing light. Idle was quite rough and timing looked like it was all over the place. Will try again in the daylight. Not an expert with timing light, but have the general sense of things.

Rotor is a tight fit on the distributor shaft, manual recommends loctite and a night upside down. That seems like overkill. Even with the tight fit, their is a minute amount of mechanical play. not sure if it's rotor to shaft or the gears on the end of the shaft. Any comments would be appreciated. Thanks.

Ayuh,.... I donno why Merc glues the rotor on, it ain't like it can go anywhere,.... I don't glue it,...

The movement is probably gear lash,... no problem,.....

 

[rocklydockly]

Thanks, it was hard to believe that small bit of movement would cause a rough idle/irratic timing. I'll recheck after work tonight. Be on the water by the weekend.

Choices, Choices .... Lake Mead or Lake Powell. (That's intended to be boastful of living in a great are, roughly 2.5 hours to either one.)

 

[ngjeldum]

Dear all, I am about to become new owner of boat with 5,7 Mercruiser 457B110HS Bravo III (duo prop) engine from 1995 Serial 0F2955xx and I am confused when reading this topic title.
I never doing research on Mercruiser and never had one before.
The seller is selling me "TBI motor", and I now assume modification has been made. Is it possible?
What was initial power rating in kW or HP of this engine? Is it originally TBI (EFI) or 2BBL? Do I have more power now that engine can withstand (not needed on 22FT Sea Ray 1995), or I risk engine damage due to new configuration (more fuel I assume)?
What would be my final check before buying this engine?
I can expect 30-35 knots maximum on 4100 - 4400 RPM (clean boat) according from what I have learned on internet? Right? If not achieved, what to check before counting money?
Thank you in advance for any opinion or clarification. The last two serial numbers are 13, if that makes any difference.

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[GA_Boater]

Dear all, I am about to become new owner of boat with 5,7 Mercruiser 457B110HS Bravo III (duo prop) engine from 1995 Serial 0F2955xx and I am confused when reading this topic title.
I never doing research on Mercruiser and never had one before.
The seller is selling me "TBI motor", and I now assume modification has been made. Is it possible?
What was initial power rating in kW or HP of this engine? Is it originally TBI (EFI) or 2BBL? Do I have more power now that engine can withstand (not needed on 22FT Sea Ray 1995), or I risk engine damage due to new configuration (more fuel I assume)?
What would be my final check before buying this engine?
I can expect 30-35 knots maximum on 4100 - 4400 RPM (clean boat) according from what I have learned on internet? Right? If not achieved, what to check before counting money?
Thank you in advance for any opinion or clarification. The last two serial numbers are 13, if that makes any difference.

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