1989 300WE 5.7 Distributors

[schwarz633]

I recently replaced the distributor caps and rotors on my 1989 300WE. The rotors were seized onto the distributor shafts and very difficult to remove. It was necessary to crank the engine to rotate the distributors in order to pry up on the rotor from opposite sides. This was done with the HT lead removed from the coil (bad idea, should have been grounded). On one of the engines I observed arcing from the HT tower on the coil to both of the small studs. Upon reassembly the engine wouldn't fire, no spark. The arcing had apparently taken out either the Thunderbolt IV module or possibly the hall effect sensor in the distributor.

After doing some research I decided on upgrading both distributors to DUI Marine HEI units from Performance Distributors. I liked the fact that the coil was incorporated into the cap and the installation would be clean and easy, eliminating the TB module and the coil. The only connections to the DUI distributor are +12V and the tachometer wire. The other option was the Delco EST which was ~ $100 more per distributor and not in stock. My starboard engine is reverse rotation so I assumed that I needed a reverse rotation distributor which was +$70 for the DUI and +$300 for the EST.

After spending a couple of hours trying to get the reverse rotation DUI distributor to drop down into the starboard engine I discovered that my reverse rotation engine doesn't use a reverse rotation distributor. I did however get the dead starboard engine running again using the standard rotation DUI distributor that was intended for the port standard rotation engine.

At this point I've only set the DUI distributor timing by ear, as neither of the (2) digital variable advance timing lights that I have will work with the DUI distributor. This has been confirmed by Performance Distributors, something about their extended dwell period throws them off. I recently located an old school non-digital timing light and will be using it soon.

I have sent the reverse rotation distributor back to Performance Distributors for conversion to standard rotation and hope to be installing that on the port engine in the near future.

 

[schwarz633]

I recently located an old school non-digital timing light and printed out some timing tapes to attach to the harmonic balancer so I could check the full advance. The old school timing light was also telling me 39° advance at idle, it should be around 8° BTDC.

I'm absolutely sure that I'm clamping the timing light onto the #1 plug wire, that's been checked multiple times. And as I've said, the engine starts and revs great. However when out on the water under load the engine wouldn't rev past 2500 RPM.

This started me down the path of suspecting that the outer ring on the harmonic balancer has slipped, apparently this does happen. Today I spent a few hours with the borescope in the #1 plug hole and rotating the engine with a strap wrench on the crank v-belt pulley (didn't want to risk breaking off the harmonic balancer center bolt). The end result is that when the piston is physically at TDC, the line on the harmonic balancer aligns with the deep notch (0°) on the fixed timing scale. Nothing wrong there.

For whatever reason, after putting everything back together I was able to get the timing set to 8° BTDC at idle with both the old school timing light and my Innova 3568. The DUI distributor mechanical advance curve is set at 24° at 3000 RPM. The 3568 advance and built-in tach function both got a little wonky at ~2000 RPM so I wasn't able to check the full advance at 3000 RPM. I didn't try it with the old school timing light and timing tapes. After reading some things today I'm starting to think all my problems were caused by clamping the timing light pickup on the #1 wire at the cap instead of the plug. The timing light was probably getting false triggered by a different wire.

Took it out on the water and it seems to run well, but the tach and sync gauge are acting a little wonky. The tach seems to read a bit high and both are intermittently bouncing around a little.

I suspect that the tach signal from the DUI distributor has a pulse width and/or shape that isn't totally compatible with what the Sea Ray gauges are expecting.

To deal with the tach instability and inaccuracy, I've ordered a Tach-Adapt from Bob at ashlocktech.com. He's confident that it will clean up the pulse from the DUI and make it compatible with the tachometer and synchronization gauge.

 

[dwna1a]

Is the tach wire good and clean as well as tight?