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Murphys

Vintage Mercruiser Ignition upgrade options

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Murphys

I am considering upgrading the ignition system on our 1987 Sunsetter Mercruiser 5.7 Liter Ski engine. The current set up is the original Mallory distributor with a Pertronix electronic conversion kit installed. Mechanical timing advance. I have been researching the Delco Voyager EST kit as well as kits from Davis Unified Ignition. I am looking for input from crewmembers who have experience and/or knowledge of these systems. Like most anything on the internet, I find mixed reviews regarding these products on-line.

The main reasons I am considering the upgrade: The local parts supply house no longer carries Mallory products and the Mallory distributor cap is a poor design (held in place by two tabs which are a pain to secure). The tabs are currently secured with a wire tie:(

 

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96Response

I did a TBI injection conversion last year and purchased the Pertronix Billet Dist. I am happy with the quality and the simple design of the the Flame thrower Module. No need for any voltage regulator or excess wires. Price was inline with everyone else as well. No complaints. Something to look into. just my .02 cents

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Woodski

@Murphys:  Another option would be to upgrade to the Mercury Thundervolt IV or V ignition system.  Simple, bullet proof and very reliable.

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oldjeep

If it fits with your intake, I'd consider just switching to a marine HEI setup.  Couldn't be easier to install and wire up.   I haven't done one in a boat but did a couple of 5.7L and 3.8L GM HEI conversions in jeeps.

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Murphys

Thanks for the quick responses. Looks like I'll be doing some more research regarding the products mentioned. 

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BoatFlyRide

Delco EST Ignition needs to be killed with fire. I'd do the self contained HEI conversion from Davis.

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oldjeep
1 hour ago, BoatFlyRide said:

Delco EST Ignition needs to be killed with fire. I'd do the self contained HEI conversion from Davis.

Davis is really nothing more than a stock gm hei system.  A whole lot cheaper to use stock gm parts. 

Edited by oldjeep

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BoatFlyRide
On 12/6/2018 at 8:23 PM, oldjeep said:

Davis is really nothing more than a stock gm hei system.  A whole lot cheaper to use stock gm parts. 

Very true. I just struggled through some issues last year. Just seems to simple to run one power wire and have a drop in solution.

 

I wish someone would make a coil-on plug conversion kit. 

Is anyone aware of one? Seems like you could use a modified distributor base to drive the oil pump and provide crankshaft position information.

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Pra4sno

X2 on @Woodski recommendation .

Thunderbolt is simple, durable, and reliable.  

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Murphys

@powbmps Would that distributor work on a carbureted engine? Excuse my ignorance, but it appears that some distributors are specific to EFI systems. I have not had the opportunity to research this issue much.

If the distributor you have will work on my engine (Mercruiser 5.7 liter ski, carbureted) then I would be interested. Thanks.

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oldjeep
54 minutes ago, Murphys said:

@powbmps Would that distributor work on a carbureted engine? Excuse my ignorance, but it appears that some distributors are specific to EFI systems. I have not had the opportunity to research this issue much.

If the distributor you have will work on my engine (Mercruiser 5.7 liter ski, carbureted) then I would be interested. Thanks.

Those hei setups work with anything.  Ive only ever retrofitted them to carb engines.  The main issue with the on cap coil versions is that they sometimes hit a intake bolt with the body.  In those cases yiu need to replace with a flat head allen bolt

Edited by oldjeep

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powbmps
21 hours ago, Murphys said:

@powbmps Would that distributor work on a carbureted engine? Excuse my ignorance, but it appears that some distributors are specific to EFI systems. I have not had the opportunity to research this issue much.

If the distributor you have will work on my engine (Mercruiser 5.7 liter ski, carbureted) then I would be interested. Thanks.

@Murphys Yes, it will work on a carb'd motor (mine was not fuel injected). Not sure what the differences are between an '86 5.7 and '95 5.7 intake, but I test fitted it with no interference issues.

I was always struggling to get my boat running right, so I was going to try simplifying by replacing the Thunderbolt setup with the DUi.  On the pre-Thunderbolt motors, it should be pretty much "plug & play".

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oldjeep
2 hours ago, powbmps said:

@Murphys Yes, it will work on a carb'd motor (mine was not fuel injected). Not sure what the differences are between an '86 5.7 and '95 5.7 intake, but I test fitted it with no interference issues.

I was always struggling to get my boat running right, so I was going to try simplifying by replacing the Thunderbolt setup with the DUi.  On the pre-Thunderbolt motors, it should be pretty much "plug & play".

Plug and play - mostly.  When replacing an old external coil setup you need to know if the existing coil is internally ballasted or if there is a ballast resistor/ballast wire on the power side of it.  The HEI setups require a full 12 volts to the distributor.

Easiest way to tell is to hook a volt meter to the coil power as close to the coil as possible and make sure you have full voltage there.  If not then you need to find and remove the ballast resistor or resistance wire and plumb in a direct 12V

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Murphys

There is no ballast resistor in my ignition system. I have the wiring diagram for my engine and it shows no resistor. This summer I verified full voltage to the coil while running when performing extensive testing of my electrical components as part of trouble-shooting performance issues that I believe have been resolved by replacing the carburetor.

I emailed DUI regarding the type of distributor needed for my engine. Their response indicated carbureted engines require a mechanical advance mechanism while EFI engines distributors use electronic timing advance.

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oldjeep
1 hour ago, Murphys said:

There is no ballast resistor in my ignition system. I have the wiring diagram for my engine and it shows no resistor. This summer I verified full voltage to the coil while running when performing extensive testing of my electrical components as part of trouble-shooting performance issues that I believe have been resolved by replacing the carburetor.

I emailed DUI regarding the type of distributor needed for my engine. Their response indicated carbureted engines require a mechanical advance mechanism while EFI engines distributors use electronic timing advance.

If by mechanical advance they mean vacuum advance then sure, although there is nothing really stopping you from running a vac/mechanical advance on a fuel injected motor.  Most after market EFI upgrades keep the stock distributor

Edited by oldjeep

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toddthelineman
On 12/5/2018 at 9:43 AM, 96Response said:

I did a TBI injection conversion last year and purchased the Pertronix Billet Dist. I am happy with the quality and the simple design of the the Flame thrower Module. No need for any voltage regulator or excess wires. Price was inline with everyone else as well. No complaints. Something to look into. just my .02 cents

I did this 2 years ago. 0 problems

Edit: While it functions as it should, it didn't clear the step on the engine cover, and the HEI rubbed on it before. I have replaced my engine cover with a different one, but make sure you've got clearance before you decide!

Edited by toddthelineman

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Murphys

I purchased a D.U.I. Performance Distributor from @powbmps . This was by far the best option financially thanks to the great deal. Thanks for the valuable  input and advice from all of you.

I will be installing the distributor this spring.

Distributor.jpg

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Woodski

Your boat looks gorgeous.

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Steve B.

That thing is a cream puff !

Steve B.

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Murphys

Thanks. It looks a little better in photos than it does in person, but it is in great shape for its age. Praying it runs as good as it looks this summer:)

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Michigan boarder

Nice job!  Great looking boat too.

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