3.0L differences

Chris1956 · 2026-07-06T06:46:01-0600

So we went from oil leak fix to water leak into engine fix?

matt167 · 2026-07-06T06:53:17-0600

Chris1956 said:
So we went from oil leak fix to water leak into engine fix?

It’s got both evidently or at least suspected water at this point… but it’s also running well enough that I doubt changing it entirely is really needed

Chris1956 · 2026-07-06T07:00:30-0600

So the leaks will be getting better? or will the manifold rust more and leak more?

matt167 · 2026-07-06T07:12:19-0600

Chris1956 said:
So the leaks will be getting better? or will the manifold rust more and leak more?

Plan on addressing them. I meant swapping to another engine.

Scott06 · 2026-07-06T08:49:39-0600

matt167 said:
Plan on addressing them. I meant swapping to another engine.

take the plugs out after it sits and spin the engine if water is leaking in after shut down you will see it come out the plug hole, or have you already confirmed that ?

Spark plug will be clean on a cylinder getting water in it as well.

If I recall you are in fresh water so rot is unlikely , but failed riser gasket or freeze damage is possible. In fresh I have had original exhaust on boats 40 years old.

matt167 · 2026-07-06T09:04:53-0600

I don’t think it’s freeze damage as there is zero signs of that as well as the PO used antifreeze to winterize. I haven’t spun it over with no plugs. Just a suspicion. #4 looked wet with oil to me but perhaps it’s oily and wet with water as well. Zero water in oil when I drained it. It’s just a feeling at this point but a gut feeling

Scott06 · 2026-07-06T09:11:42-0600

matt167 said:
I don’t think it’s freeze damage as there is zero signs of that as well as the PO used antifreeze to winterize. I haven’t spun it over with no plugs. Just a suspicion. #4 looked wet with oil to me but perhaps it’s oily and wet with water as well. Zero water in oil when I drained it. It’s just a feeling at this point but a gut feeling

oil makes sense given the age of the engine. But usually water will steam clean the plug. Easy to take them out and spin it after it sits.

On the initial stumble might use a spark gap tester on all four plug wires to see if you are loosing spark. Might just be a carb por choke setting that smooths out when it gets warm. If i recall on my 3.0 two plugs always looked perfect and two always looked black/somewhat fouled. I think ends were fouled, and middle cyl were ash grey. Never could make that go away ran great after rebuilding the carb and hammered that boat for 20 years. Always amazed how much punishment the 3.0 could take as the kids got bigger and load on the engine when tubing and skiing increased

Chris1956 · 2026-07-06T09:41:43-0600

Gee, it will be simple (and cheap) enough to fix the oil leak, when you pull the engine. Set up some cement blocks and wood to hole the block while you pull the pan.

Mark the exhaust manifold so you remember it leaks and store the engine.

matt167 · 2026-07-06T18:13:38-0600

Scott06 said:
oil makes sense given the age of the engine. But usually water will steam clean the plug. Easy to take them out and spin it after it sits.

On the initial stumble might use a spark gap tester on all four plug wires to see if you are loosing spark. Might just be a carb por choke setting that smooths out when it gets warm. If i recall on my 3.0 two plugs always looked perfect and two always looked black/somewhat fouled. I think ends were fouled, and middle cyl were ash grey. Never could make that go away ran great after rebuilding the carb and hammered that boat for 20 years. Always amazed how much punishment the 3.0 could take as the kids got bigger and load on the engine when tubing and skiing increased

1-3 were slightly tan not perfectly steam cleaned white like I would expect. 4 was black. It now has 4 new plugs. I can’t remember the number but I looked it up and same number AC Delco that came out. I’ll have to check the plugs when I get to the boat this weekend.. this engine has DDIS with the single coil. Is the DDIS coil 2 banks or one single batch fire bank? I’m just thinking perhaps one bank is going out and it’s actually missing on 2. I have an old school Mac tools spark tester though I’ll bring with me

Scott06 · 2026-07-06T20:03:21-0600

matt167 said:
1-3 were slightly tan not perfectly steam cleaned white like I would expect. 4 was black. It now has 4 new plugs. I can’t remember the number but I looked it up and same number AC Delco that came out. I’ll have to check the plugs when I get to the boat this weekend.. this engine has DDIS with the single coil. Is the DDIS coil 2 banks or one single batch fire bank? I’m just thinking perhaps one bank is going out and it’s actually missing on 2. I have an old school Mac tools spark tester though I’ll bring with me

DDIS I thought was distributor less with a coil pack individual coils for each cylinder, there was a sawed off distributor base that drove the oil pump and was the trigger for the spark , essential a crank position sensor, an amplifier module and the coil pack were on back of stbd side of engine above starter

I had this on my 3.0, merc only used it for A handful of years before going to delco est . Issue is with DDIS even years ago all the parts were NLA, so only choice is to got to est. I never had an issue even plug wires were original at 25 yrs old.

matt167 · 2026-07-06T23:19:48-0600

Scott06 said:
DDIS I thought was distributor less with a coil pack individual coils for each cylinder, there was a sawed off distributor base that drove the oil pump and was the trigger for the spark , essential a crank position sensor, an amplifier module and the coil pack were on back of stbd side of engine above starter

I had this on my 3.0, merc only used it for A handful of years before going to delco est . Issue is with DDIS even years ago all the parts were NLA, so only choice is to got to est. I never had an issue even plug wires were original at 25 yrs old.

It has the crank sensor, an ignition controller box and the one coil with 4 posts on it. I just don’t know how many connectors it has. I’m wondering if it’s a waste spark system

Scott06 · 2026-07-07T05:05:52-0600

matt167 said:
It has the crank sensor, an ignition controller box and the one coil with 4 posts on it. I just don’t know how many connectors it has. I’m wondering if it’s a waste spark system

I don’t think it’s a waste system as I think there are 4 coils in The pack . I think I have some documentation on it somewhere I’ll see if I can post it

edit I stand corrected, you are right there are two coils see attched pm me if you want The Who manual

3.0L differences

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