I am reading the engine manual for this boat. It has the Mercruiser 340 engines. One port and one starboard. And it refers to engines the rote Clockwise and engines that rotate Counter-Clockwise. Does the port engine rotate in one direction and the starboard engine in the other direction? I'm asking because the plug wires go into the distributor cap differently for the CW and CCW rotating engines and that might be why the port engine doesn't start. The plug wires might be installed incorrectly on the distributor cap.
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1984 CC Commander 315 MIE 340 engine rotation question.
1984 CC Commander 315 MIE 340 engine rotation question.
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Comments (6)
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The port engine is normal rotation and the stbd will be reverse rotation.
If they are like my 350Q engines, the crankshafts run opposite directions, but the cams and distributors run the same direction. The firing orders are reversed, and the wires to the distributors are very different orders, not just opposite.
Merc did things the same as Scott described. Port engine should be standard rotation, starboard should be reverse rotation. Both cams and distributors spin in the standard direction (cam should be gear driven on the reverse rotation engine). Firing orders are listed as follows according to the Merc book:
Standard rotation: 1-8-4-3-6-5-7-2
Reverse rotation: 1-2-7-5-6-3-4-8
As another thing to check, once you get them both started, check the ignition timing. Assuming the original Thunderbolt IV ignitions are intact and have the standard V8-24 ignition module, you should show 8* BTDC at idle as long as it's idling around 800 rpm or less (depending on your idle setting you may need to check this in gear to get the RPM down).
To keep the damper plates on the Velvet Drive transmissions happy, make sure your idle speed is set between 650 and 700 RPM in forward gear when tied to the dock (check with teh engines fully warmed up). It'll be higher in neutral or when moving. Getting it in spec should avoid damper plate rattle from RPM dropping too low or stalling, especially when maneuvering while the engines are still warming up.
If you want more detail, I've got a PDF of the original Merc service manual for these engines, feel free to reach out if you want it.
Hello Robert.
Well, I'm living on the boat now. On the hard in a Marina in Port Clinton OH.
I had spark last Friday to the STBD engine. It would run breifly with Starting fluid. Found a faulty fuel pump. Fixed the fuel problem last Sunday and when I went to try it again now I don't have spark from the coil to the distributor. Can you send me a copy of that PDF file you have of the Service manual for these engines. I have a 1984 Chris Craft Commander 315 witht he Mercruiser MIE 240 engines. Thanks.
An engine can start and run on starting fluid, with no spark. The compression is enough to get ignition. I've pulled my hair out trying to figure out why my spark was intermittent, when it was never there.
John, I can't view your profile for some reason. Provide me an email address and I can send over a copy of the service manual PDF.