low hour 2000 4.3 Mercruiser starting & running too rich to run...

[Lou C]

OK a few things I noticed:
the rust on the valve springs and heads, suggests water intrusion, besides the broke valve springs. I would think with that many valve springs broken (unusual in my experience with a 4.3) the engine may have been over-reved in the past. Is the boat over-propped?
​water intrusion can come from those one piece manifolds (weren't they known for that, this has been commented on many times on this forum)
​also, water intrusion can come from a bad head gasket, and head gasket damage that lets water in a cyl and in the oil, does not always show on a comp test. I had this same issue myself last year. I had 2 blown head gaskets letting water in but the comp test results were close to normal. So you should test the exhaust manifolds for leaks and look in the exhaust ports of both the manifolds and cyl heads for rust. I'd for sure crank it over with the plugs out and ignition disabled and check for water in the cyls. If so I'd try to pressure test the cooling system. I rigged up a dynamic test for combustion gas getting into the cooling water, sure sign of a blown HG.....watch what happens at the end of the vid when I shut it off......

https://www.dropbox.com/s/8lz4p4e7pdrtqr2/summer and fall 2016 232.MOV?dl=0

​did a top end rebuild with a pair of reman heads and new gaskets, and center riser exhaust conversion:

https://www.dropbox.com/s/55j6h4dd1u8fv0k/IMG_2273.MOV?dl=0

 

[Lou C]

Did a bit of reading on what causes broken valve springs, apparently rust can cause that.

 

[Porschesolutions]

Ok well the last ?mechanic? had merely dropped in the distributor w/o care of rotor orientation and then rearranged the wires on the cap to follow the firing order. So now, TDC is at about 1-o-clock when looking down on the distributor. It runs and idles but won?t rev out or anything so we?re now back to crappy running conditions. I?ll redo the compression check tomorrow night and ensure I?m still golden there. I?ve also completely forgotten the baseline needle and set screw settings on the carb since I?ve rebuilt it and perhaps jacked with it, so I gotta freshen up on those two and ensure I?m getting spark to all 6 plugs. I pulled no1 with it running with nitrile gloves on but was still jolted a bit

Yes the broken valve springs on #3 & 5 showed extensive rust on them. I replaced all on that bank.

 

[Rick Stephens]

Get your timing set perfectly with a light. Matters not a bit where #1 TDC is as long as the wire routing works and is neat.

I would replace the rest of your springs. Can't see doing half a motor.

Turn your idle screw down until they just touch bottom (gently) then back them out 2 turns. Use a tach and adjust evenly to highest RPM.

 

[Lou C]

I think the problem in the background is water intrusion. Better get that tracked down or more problems will come. Ask Bondo and others about those one piece Mer manifolds. While I never had problems with my OMC one piece units, I have heard that people have, if they ran them too long and they rusted internally. There is a one piece to two piece conversion kit available from Merc and from Barr aftermarket if I recall.....
​Basically you should not have ANY rust on the valve train. My boat has been used in salt water for over 15 years and is stored in a damp coastal salt water region. Before I had the HG problems last year there was NEVER any rust on the valve train. Even after there was only a few spots on a pushrod. To those that say the corrosion resistance claims of the NMMA FWC oils is BS, I refute that. The salt water was in the engine at least a week and a half and here are the heads.....

https://www.dropbox.com/s/1yyauruiipe64mq/4.3 old cyl heads .JPG?dl=0

 

[Porschesolutions]

yes on the timing: gonna try to tackle that in the next few evenings; once a compression test (again) shows that I'm still golden. I have no oil in water, no water in oil, good compression (last time I checked) across the board.

The side of the motor that has the mounts for the cables appears to be much more complex in removing: i have not yet removed all that to pull the valve cover to look for rust on that bank (2,4,6) of cylinders.

 

[Lou C]

What I'd do first:
​Remove both exhaust manifolds, look in the engine cyl head exhaust ports for signs of water like rust trails. Prop the manifolds up level, then carefully fill with acetone and wait a bit. See if you see damp spots appear in the exhaust ports that is a sign of small water leaks in the cast iron. The acetone has less surface tension than water and will find a smaller crack than water will. Because rust under the valve covers is a sign water is getting in someway, and while water may not be showing up like a milkshake yet, it has to be there in small quantities, the kind of thing an oil analysis will show. Either from the exhaust manifolds, an intake manifold gasket leak, cyl head gasket starting to leak, or a cracked cyl head (not likely unless a bad overheat happened).
​Keep in mind that normal comp. test results does not mean a head gasket can't leak water into a cyl.

 

[Silvertip]

Deleted

 

[Porschesolutions]

Ok progress- ignition timing was WAY off- with the Purple/White wire grounded, timing showed to be about 10 degrees ATDC. I advanced it to 10degrees BTDC which places the 10 degree tick on the balancer on the largest V on the timing tab. Doing this made me lower my idle and play with my mixture simotaneously until I was down to about 650. It starts right up and idles with the throttle straight up now. Unsure how rich or lean I am as it?s kind of boggy just off idle but then shoots up to 2500-3k pretty quick and smooth. Back to idle it continues to maintain a mostly smooth idle. Had to re-set timing a few times as I adjusted idle and mixture. Will go back out tomorrow evening for a bit more.

Timing does advance with the ignition turned off and grounding lead removed from the Pur/wht wire and yes this wire end had a rubber bullet stopper installed as I saw on a YouTube video- kinda cool that it was still here plus helped validate I had the correct wire .

Suggestions on the mixture screw and helping reduce/remove bog just off-throttle??

 

[Rick Stephens]

Suggestions on the mixture screw and helping reduce/remove bog just off-throttle??

Stronger needle springs. That is how you add a bit of fuel right as you start opening the throttle. (I am remembering correctly that you have a 1409?) If you already have the strongest springs then you need smaller/shorter needles.

Timing is timing. Once set, you shouldn't be changing it to make up for carb tuning issues. Set it where the book says and leave it alone.

 

[Porschesolutions]

No Title

Here's a file I made showing before/after timing changes. There are NO photos or videos anywhere showing this...I'm hoping i did it correctly though the boat does run MUCH better now

 

[Porschesolutions]

nobody? is this thing on? Tap tap

 

[Lou C]

I have not looked closely at newer 4.3 but on the older models like mine the timing marks are on the port side of the engine, or the right hand side as you are facing the front of the engine. On my '88 OMC the factory setting is 6*BTDC. Yours appears to be on the other side or am I seeing that wrong?

 

[Porschesolutions]

Unsure though the boat starts/runs "near normal" with how I changed it. :/

 

[Lou C]

well which side is your timing tab on?

 

[Porschesolutions]

now my timing is set at the 10 degree mark (on the Harmonic Damper) in the middle of the largest V on the motor, with the advance bypassed (ie, purple/white wire grounded). Verified purple/white & grounding changes ignition timing BTW, so I know that's correct. Got a few jolts through my nitrile gloves while turning the top of the Disty to set timing, so just replaced all 7 wires with new.

 

[Porschesolutions]

Here's an update folks:

Took the boat out in February for a semi-ok boating experimental tuning trip, but started acting weird again; brought it in & found no compression in #6 and slightly mixed water in the oil. Also found water in the trim reservoir. Decided to do full valve job.

1. Machine shop xrayed the heads & intake, pressure tested the wet manifolds: found that #3 cylinder (head) was warped, so decked the heads so that the new marine gaskets would seal.
2. No valves were bent, so relapped them, painted everything, put it all back together with Quicksilver/Sierra/Mercruiser gaskets & followed the manual for sealants, torque values, etc.
3. Water shutters: eek: one was collapsed, the other was collapsed and torched! Bought new Quicksilver shutters.
4. Did 3 oil changes to clean out the slightly-contaminated oil.

I now have perfect compression across the board with all new valve springs, valve stem seals, etc.

Time to re-set carb, re-check timing (ugh), and hopefully get it running decent.

THEN to figure out why water is getting into my trim tab reservoir!

 

[Porschesolutions]

Oh, my torched water shutter: FAIL. Old vs new

Cold, dry compression numbers

 

[Rick Stephens]

Nice neat repair job. Amazing what one little rubber and tin component can cause.

 

[Porschesolutions]

Well that was part of the problem, though the warped head didn't help. Here it is after planing...was not detectable prior to planing- headgasket looked fine too.

Machinest figures it was sealing enough while cold, but not fully warmed up. The oil was only barely contaminated with water...not full-on milkshake.