Author Topic: Need some help - ignition options for mercruiser v8  (Read 1729 times)

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Offline Mootspoints

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Need some help - ignition options for mercruiser v8
« on: August 14, 2023, 01:12:42 PM »
Quick background.  Recently acquired a '79 CVZ-18 sight unseen.  There's a lot of other background, but currently working on an ignition problem.

The engine is labeled as a 228, but the prior owner reported that he put in a 350 short block after the motor wasn't winterized and cracked the block (I'm hoping not an automotive, but who knows).  The distributor / ignition had been replaced with a generic, integrated coil automotive distributor.  It had a weird issue where it got spark to start, but lost spark as soon as the ignition key went back to run.  I pulled and reinstalled the coil and it started working again...  Who knows about that.  Anyway, it's also running really rough at low RPM after driving it around a while.  My theory is that there might be high humidity / moisture in the distributor cap as it's not a sealed unit and there is some misfiring going on.  I'm not certain, but either way I don't like having this non-marine ignition in the boat.

So my question: what is the best option for replacing the ignition on this thing?  Back to a thunderbolt?  If so, what components do I need?  Is there a better aftermarket option I should look at?  I'm not super concerned about cost, but I also don't want to spend $600 if it doesn't come with any performance advantage.

Thanks!

Offline carlsoncvx18

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Re: Need some help - ignition options for mercruiser v8
« Reply #1 on: August 14, 2023, 03:08:13 PM »
I would look into a pertronix  distributor you need a coil to goo with it. Converted my points ignition to there bolt in set up never have a problem. 
« Last Edit: August 14, 2023, 03:12:25 PM by carlsoncvx18 »
1987 CVX18.     1968 Glastron alpha sail boat
1977 GT150
1986 CV23
1984 Intimiadator
1981 CV27
1969 V-180 fundeck

Offline thedeuceman

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Re: Need some help - ignition options for mercruiser v8
« Reply #2 on: August 15, 2023, 06:13:56 AM »
I?m not sure when they switched to the thunderbolt on the Chevy motors, but If the 79 originally came with a points distributor, there?s a ballast resistor (resistance wire) lurking in the wiring harness. if that?s in there, the HEI style ignition would have problems, and the spark, while cranking would also be explained because it?s bypassed when the starter solenoid is pulled in.
And I agree with Jeff on the pertronics.


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Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline Plugcheck

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Re: Need some help - ignition options for mercruiser v8
« Reply #3 on: August 15, 2023, 09:34:42 AM »
It is important to run a marine rated distributor even if the points are replaced with an aftermarket ignition module.    Lots of sparks floating around inside that cap should any fuel vapors be hiding in the bilge.    Joe is correct concerning the ballast resistor, it limits the current in the coil during run, but is often bypassed when cranking for a bit more spark.     I also have a 79 cvz-18 running a Mallory dizzy with pertronix 3 and pertronix super coil, crab cap/rotor.    My dizzy was points on the 898(305 2bbl).  Have had no issues in nearly 10 years ignition wise, just don't use solid core wires, use suppression type.    Pertronix and other solid state ignitions don't tolerate the emi/rfi very well.     Good luck, post pictures!
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline Mootspoints

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Re: Need some help - ignition options for mercruiser v8
« Reply #4 on: August 15, 2023, 01:09:53 PM »
Hmm?. Thanks all.  Know where I can find the ballast resister and can it be removed if there?  The engine was originally a 228 305 4bbl.  It does run, but sometimes not well. 

What coil should I source with the pertronix?

Will get pictures soon.

Offline Plugcheck

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Re: Need some help - ignition options for mercruiser v8
« Reply #5 on: August 15, 2023, 06:16:17 PM »
Go with the coil that matches the electronic ignition.   I bought my pertronix as a package ignitor/coil, then you are assured of the hottest spark and compatibility.
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline Mootspoints

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Re: Need some help - ignition options for mercruiser v8
« Reply #6 on: August 16, 2023, 05:38:23 AM »
Okay, ordered from Jegs.  Will be here Thursday and report back how it works out.

Offline Mootspoints

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Re: Need some help - ignition options for mercruiser v8
« Reply #7 on: August 27, 2023, 07:56:42 AM »
Closing this out.  Had a couple unforeseen roadblocks, but finally got the new ignition in yesterday and got the boat on the water.  Wow!  What a difference it made.  Idle is better, acceleration is waaaay better and the whole thing just works 100% better than it was with the weird auto HEI unit.

Used a pertronix distributor, pertronix 8mm wound RF resistant wires, pertronix flame thrower coil.  Changed all the spark plugs to factory AC Delco and gapped to .040 (+.005 over factory per pertronix instructions).  Left the silver springs in the mechanical advance which is supposed to start advance at 1k and have full advance to +24degrees by 2k.  Set at 8 degrees at idle.

I think I can go more aggressive on the timing still, but for now it?s great as is.  Thanks for the help!

Offline Plugcheck

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Re: Need some help - ignition options for mercruiser v8
« Reply #8 on: August 28, 2023, 08:06:11 AM »
Most of the SBC engines like 28-32 degrees total advance.   Great to hear you're back up and running, go enjoy some time with your CVZ.
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline demian5

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Re: Need some help - ignition options for mercruiser v8
« Reply #9 on: August 29, 2023, 05:40:53 PM »
Personally its easier and cheaper to have another set of points and condenser on hand than a spare petronix...

Just sayin...
1979 Glastron Carlson CVX 16 SS I/O Mercruiser 140 "Brick House"