Havasu Hangin

Don't mean to scare you.

One time, when I changed my pan, they gave me the wrong dipstick...and I didn't realize I was overfilling the pan. Very few symptoms, but the pressure was a little erratic. I don't think that's your problem, but it doesn't hurt to check...

I think all these guys are right on track. When troubleshooting, I tend to start with the simple things, like making sure the linkage is set correctly, wires, etc.

Something I just thought of...did you have an external ballast resistor on the stock coil? I think that MSD coil has an internal one...just a thought.

Jeff

olysan

I'm not sure about the ballast resistor? My ignition is staright stock T-bolt IV salvaged from my old 350 magnum. When I changed out the coil I just swapped the wires over nothing else.

Havasu Hangin

I'm not familiar with that ignition, maybe someone could chime in. On my old Volvo ignition, the ballast resistor was mounted in-line on the wire to the positive side of the coil...it was fairly close to the coil. It was an inch or so long, and had plugs on each side.

The resistor limits the voltage to the coil, to keep it from self-destructing. If you still have a resistor in-line with a coil that has an internal one, you may get a very weak spark. Hard starting, power loss, etc.

A quick test would be to put a voltmeter on the positive side of the coil while it's running (or the key on). You should get 12-14 volts. If there is a resistor, it may only read 10 volts or so.

Once again, just thinking out loud.

olysan

I pulled the plugs this morning. 1 & 3 look like new almost like they've never even fired. The wires were tight when I pulled them, and I verified my firing order. The rest look pretty good, a couple were a little on the dark side, and a couple were a little to clean looking, but generally pretty good except 1&3. Could this be a coil related problem or does this indicate something else?

Havasu Hangin

Generally, if they are not firing, they will smell like gas.

If I want a quick test to see if they are firing, I will usually take the wire off, and place the exposed (brass) end 1/4" from the engine block. Now, crank the engine for a couple seconds...there should be a spark jumping from the end to the block.

As for the coil, a weak spark may cause this...but there could be other reasons. If unsure, Perhaps you should throw the old coil back on to see if there is a difference.

If there is a strong spark, and at the right time (firing order, timing checked), and the plugs do not smell like gas, then I would look for a fuel problem.

Did you verify the valve adjustment? Also, I don't want to concern you, but those cylinders being next to each other, perhaps a leakdown test is in order, just to be safe.

blue thunder

Just curious... how did you set the valves initially? Should be 1/2 turn of the rocker nut after the push rod stops spinning freely. Can you hear any valve train ticking?

BT

Spanky

I'm with Havasu....throw the old coil back in and check it then. Also, there is no sure fire way to check your cap other than replacing it. Even a slight drop would be enough for a hairline crack (invisible) and thats enough to ef everything up........

olysan

Okay, the heat index was 110 here today and my driveway (where I work on the boat) gets sun all day so I didn't get to the valve train.

I don't remember a strong gas smell when I changed the plugs. Not sure if it matters, but the engine hasn't run since thursday. I did notice some oil on #1.

I did change the plugs to champion RS12YC gapped @ .040 - exactly what I ran last year, and I did replace the MSD coil with the original merc coil. I also checked my throttle adjustment, and it was good. When I started the engine it seemed to run significantly smoother, so I thought I might have solved the problem.

WRONG! I pulled the boat up to the nearest launch, dropped it in and hit the gas. Same sluggish acceleration and no top end. It seems to run fine no strange noises just a dog. I had the GPS with me today, and top speed was 42 @ 4000 rpm. That's a loss of 12 mph, and 1200 rpm.

I'm going to take a look at the plugs tomorrow morning, and try and adjust the valves next week sometime.

Blue Thunder - I used the procedure that you described. I guess my concern is that I might have had the crank 180 degrees out. At times I hear what sounds like 1 or 2 valves ticking, but that's it.

Thanks everyone for the help to this point.

Mike

blue thunder

When setting valves, I always turn the crank until about 1/8 rev past when the intake valve closes, then I do that cylinder. I continue this on each cylinder. 180 out doesn't mean anything this way. Also.. others disagree, but I don't like setting the valves with the engine running... too much uncertainty.

BT

Havasu Hangin

There was a guy on another board...he raced Pro Street I think. Anyway, on his boat, he never adjusted his rocker arms past pushrod resistance on his hydraulic cams- he said it was worth 20HP more on the dyno....for a loose valve train.

olysan- still thinking outloud...perhaps you could throw an ohmmeter on each plug wire...you may have damaged the core(s) during the r&r.