Plugs
 

Just had this motor rebuilt and pulled the plugs after a few outings. #2 clearly looks rich and #7 not as bad, the others look okay to me, but what do I know.

Running a 1050 dominator. What carb settings could I look at to lean up #2 a little and #7? These were pulled after a 30 miles trip at good RPM with a little idle when trailering. I'd think they're pretty representivive. I checked timing and I'm showing 40* all the way up to 5000rpm. I'm supposed to drop it back by for them to check with their gun, but I think it's about 6* too high. They told me should be 34* above 5000. This is one of the reasons I decided to pull plugs to see if they were loose or any signs of detonation.

https://flic.kr/s/aHBqjA81HD

Thanks,
Todd

40*!!!!

That sound like a lot of timing to me.....

it sure does and the shop is stringing me along versus just verifying it. That’s another story. I just got the motor back so I don’t want to make any changes at this point. This is how they gave it to me. Engine was apparently on the dyno as well, so not sure how we’re 6* off. I don’t feel safe driving it with potential
for detonation.

they told me it should be 34* above 5k RPM… what about 3-4900 RPM where it spends 90% of its life.

Looking thru my phone my eyes went to cyl #6 for now.
Appears to me like many pepper marks.

”Detonation shows up on the plugs as spotting on the porcelain. There are two different types of spotting seen. One type appears as just black spots and the other appears as little bright spots like diamonds. The black spots (look like pepper sprinkled on the plug) indicate a little too much heat on the plug which causes detonation by having the heated plug fire off the mixture prior to the spark firing. This creates two flame fronts that collide and can cause great amounts of damage. If you see black spots on the porcelain and you know the tune-up is correct then you may need a colder plug. If you are not sure then increase the carburetor jet size slightly, take out some timing, or go to a colder plug. If you hold the plug in the sun and you see what appears to be small diamonds on the porcelain then your detonation is severe enough to be blowing off the aluminum from your piston and you need to add fuel and/or take out timing now.”

Great eye. It even looks like the electrode is worn down compared to the others. This has maybe 5-10
hours on it.

40* is crazy. Must be a light boat, don`t think 40* at peak cylinder would last 10 minutes in my tank.
I`m running closer to 26-28* depending on boost.
You need to get that sorted asap.

Yup.
That was discussed on his other thread. Not sure why this thread (i’d suspect some detonation) as his type heads and compression typically use 34-35 degrees.

Yes this is NA at least but still. Shops telling me it was set at 34, my gun shows me 40. I’m a technology guy, so I trust the guys that have been doing it for 30 years, but something seems off. This is a big miss for them if the timing is actually at 40*.

Little things like a faulty fuel pressure gauge they didn’t change, but knew was was bad. That caused me a day troubleshooting on the water, getting parts, only to find out they knew the gauge never worked. Missing nut that connects the lower/upper drive. Little things that make me lose confidence in what they delivered.

Not trying to duplicate posts and issues here - I’m not worried about my post count 😂

Really wanted an opinion on what you all thought on the plugs. Doesn’t change the timing issue I think is going on.

All good. Round table talk. :)

Curiosity, what Autolite # ?

3924. Dart 310 heads. I didn't verify, but know they mentioned the wrong plugs were in it previously. They were about .5" too long and the ground electrode had come off on one plug/cylinder.

an autolite 3924 is 3/4" long. what was in there before that was longer? any one know were this plug heat range falls on the chart? hot, cold or middle?

It’s a pretty hot plug from what I’ve read.

no idea what was in it before the shop pulled them during the rebuild.

In NGK speek, it’s a heat range 5.
Most Mercruiser blue motors (500hp, 500efi, 525efi) use a heat range 6 plug. 6 is 1 step colder than 5.

What I found.
See last page (4) here:
https://www.autolite.com/docs/defaul...heat-range.pdf

Autolite 3924 crosses to NGK 7373 FR5 V-Power Spark Plug and NGK 7938 BKR5E V Power Spark Plug

One step colder Autolite 3923 crosses to

NGK 6962 BKR6E V-Power Spark Plug

As a note, the BKR6E cone gapped at .031” . I set to .035” just because :)

Weird mistake to have happened because most aluminum bbc and sbc take 3/4” (.750”) reach gasketed spark plugs.

Ive used quite a few autolite 3923 in aluminum headed marine engines in the 8.8 to 10-1 arena, a 3924 typically too hot

How old is the balancer? They set the timing before doing any hard dyno runs and the ring could have slipped and now reads 40. Get a piston stop and check your timing mark. 3924 is recommended by AFR for Pump Gas, I run them in my motor and they are not too hot based on the ring on the electrode. But my motor runs super cool anyway. You definitely have some distribution issues. Even bank looks a little rich across the board with 4 and 7 really fat. I would try a 1" tapered spacer with a 1" open to try and get better distribution. When I pull my plugs you can't tell one from the other and I'm running a custom 1000CFM 4150 on a Brodix HV2000 intake with both spacers I mentioned.

those 2 black plugs are something wrong wires not on correct cyl? cam firing order swap? black and wet is not firing

I just got a look with little better video screen at #6 plug and it’s really concerning.

8 7
6 5
4 3
2 1

I've been trying to get the shop to get me in to check the timing and plugs for 3 weeks. I guess the motor left the shop and they're done with me. I'm going to give him another chance to respond tomorrow before I just cut my losses and go to another shop. Still haven't received the build sheet and I picked up the boat over a month ago.

I checked wires before my last outing and #2 almost didn't feel like it was on good. I was hoping for an improvement, but no change. I will verify the firing order again to rule that out. The boat feels down on power from what I would expect and the timing is all out of whack. You'd think this place would want to get me in. I even told them I'd pay labor if everything checked out. For F*CKS sake.

You don't think it's firing at all on those two cylinders?

They reused the balancer, so it's probably got some hours on it. I had a really nice Holley marine 1050 on it and he said somoene had drilled on it and he couldn't jet it enough, so he ended up putting on some old BG 1050. I wish he would've called me because I would have picked up a pro systems or a new one, this thing looks janky.

I may actually have an old HVH super sucker I ran on my car years back. I'll see if I can dig it up and give that a try.

BTW I have the plugs facing like you're looking at the engine, so it's the odd bank and #2 and #5. Not that it really matters, issues at the end of the day.
8 7
6 5
4 3
2 1

Appreciate all the advice man!

#2 and #5 are fat and according to what you're seeing, #6 is either lean or detonation?

Amazing this thing was apparently dyno tuned too.

Detonation.

Here is your #6 close up.


https://cimg5.ibsrv.net/gimg/www.off...431fca5486.png

Thank you. Based off your precious post it’s the actual porcelain you’re concerned with? I see the peppering you’re talking about.

does the ground electrode show anything that would also mimic detonation?

Glazing on porcelain shows rich at idle.
Black specs show detonation typically from too hot plugs and/or timing.
More detonation would show up as tiny aluminum balls down towards bottom of porcelain. You need a good kight snd sometimes magnifying glass to see it.

I’d set total timing to 34.
I’d run a colder plug. The autolite 3923 or ngk bkr6e. Maybe even bkr7e for now to play it safe ? Gap any of these to .035”.

btw: slightly off topic, but since it will be effected when you change total timing, what is your initial timing ?

Go to Walmart and get yourself an Otoscope in the pharmacy department for checking your plugs. Best money I ever spent. If you had 2 cylinders not firing you would have a hard time getting on plane and it would shake something terrible. What ignition are you running and what wires? Check the jets on the carb to see if they are the same on both sides as well.

This is a DUI7000, new MSD wires were installed as well. Not sure on the jets since I still haven't received the build sheet.

Shop just text me back and said: "if the plugs look like this after normal boating then they're fine. It's a carburetor with a big plenum."

I find a spark plug magnifier is a great tool to see the plug but I still don`t know what I`m looking at .
I thought the ground strap tells the timing story ...


https://cimg6.ibsrv.net/gimg/www.off...0bed11a11f.jpg

If that`s aluminum peppered on the plugs like SB said then it`s not so fine.

Yup. Pretty much.

I'm taking the boat to the shop tomorrow to have them check timing - not sure if they'll just check it or have me leave it. Would be nice to just check it and save me anouther hour and a half roundtrip. Once timing is checked/confirmed, I'm going to put a new set of plugs in and see how it runs. Shop said the plugs look fine and attributed the plugs to a large plenum and dominator.

On another note, kicking around the idea of a new set of heads and cam over the winter. Kind of wish I would've just ponied up when I had the motor out. I have maybe 10 hours on it now and a fresh set of Dart 310's if anyone is looking :) I was looking at the AFR 335 CNCs and realized Tony is no longer with AFR and started up his own company. He is a 340 full CNC (MMS 340) marine head I'm going to talk with him about today. I also have another shop in mind for this work.

I did a compression test today. All cylinders look great 150-153 across the board.

Dropped the boat off today. He’s going to check timing and mess around with the advance. Plan is to swap this DUI unit out over the winter with an MSD. I’m going to put the BKR6ES plugs back in it instead of the 3924s.

hope to get it out this weekend if the wife let’s me 😂

Well it looks like the limiter bushings we’re missing which caused the erratic timing. This was the same disti I pulled off the old setup so he just put it back on without going through it. Now full advance is 34*.

I also swapped plugs to the BKR6ES-11. First impression is great. Cold start / idle is night and day.

Hope y’all are doing good! Appreciated all the input so wanted to let you know where I’m at.

As previously mentioned, timing is now at 34*. Didn’t seem to lose any power considering it was at 40* before.

I ordered a new in box Mercury 28p Bravo1 LH that came in Friday. Swapped it out in place of the 26p and went for a test run this morning. 4 hours of driving for 30 minutes of boating but totally worth it 😎

it came on plane great. Just as good or maybe even better than the 26.

RPMs dropped from 5800 > 5400 which is great. I’m running the exact same MPH @ 72.

If I run those numbers through a slip calculator with my 1.5 ratio, interestingly enough I’m seeing the same 25% slip with both props, 26 and 28. Just at a lower RPM, which I’ll take.

Scratching my head on the slip numbers still. Fair enough to say the prop is ruled out. Not sure if this IMCO lower -0 standard height is hurting anything… the hull looks pretty good overall. There is some bad gel coat patch work right near the step on starboard side. I want to get that cleaned up but don’t think it’s the culprit.