Another ProTec Conversion

Near the end of last summer, our '94 SN with the ProTec ignition and EFI/throttle body was no longer behaving nicely.  The motor wouldn't fire regularly whether warm or cold.  The idling never settled below 900 rpms, and the exhaust smell indicated a rich mixture.  The last time on the water we almost couldn't get the engine started in order to load up onto the trailer.  It was at that point I consulted the forums pages here and learned from many people who discussed their successes with converting to a carburetor and distributor. 

In December, under a shade tree out back, I slowly stripped away the original factory equipment: fuel pumps (2), ignition control module, EFI control module, trigger assembly, MAP sensor, throttle body, and the wiring harnesses supporting these components.  By the end of February a new DUI distributor, spark plug wires, fuel pump and a power source for the distributor were installed.  Unfortunately, this happy little boat project is now stalled due to carburetor shipping delays. 

Like others, I chose the Quick Fuel M-600 marine carburetor.  I purchased directly from Holley in January.  It was out of stock at the time yet the initial shipment date was mid-February.  Then it moved to early March.  Then late March.  Then early April.  Now, Holley says, "Coming Soon."  Mr. Holley:  If you're reading this, coming soon can't be soon enough.  I considered the M-650 but it too was out of stock.  I even looked at the refurbished ones.  No stock.  I wonder whether this has happened to anyone else.

This has been a fun off season project.  I owe endless thanks to Jonny Quest with his outstanding technical guidance and mentoring.  He, along with all others who ever posted comments on previous ProTec conversion procedures (yes, I read every posted topic,) deserves recognition for helping keep these boats running well.

Matt

He's out there in the same state as you

Done deal.  May those old parts find a good home and provide years of service on the water.

Thanks KENO!

Another Update:

Despite earlier whining and complaining, I landed a new Quick Fuel M-600 carburetor and mounted it up over the weekend.  The installation was very straighforward.  The only thing needed was a reposition of the original throttle cable linkage.  The bracket had multiple holes pre-drilled so it was simply a matter of finding the right orientation for the socket on the cable to mate with the carb actuator ball.

Rather than spritz fuel into the butterflies, I turned the key two times for no more than 7 or 8 seconds.  By this point fuel was visible in the sight glass of the carburetor.  With the throttle cable detached, I moved the carb throttle lever and saw and heard fuel spraying.  As I gave the key a short quick flip to the start position, the mighty 351W roared to life like never before.  The idle was elevated a bit.  I then set the base timing at 10 degrees BTDC.  Now it's time for an off the trailer water test.  

For a card carrying novice like me, this was pretty exciting.  This 30 year old sleeping dragon has broke free from the ProTec chains of the past.  Without the input, consultation and guidance from the well informed Correct Craft Fan members there's none chance I would have been able to get this boat running. 

On the water testing has produced fairly good engine performance results.  The QF M-600 is solid and meters the fuel just as described right out of the box.  Along with the help of a digital timing light, the curb idle screw needed some minor adjusting to get the RPMs down to 700-725.  Fuel inside the bowl is visible half way up the sight glass.  Setting total advance timing with the DUI distributor, however, is giving me fits.

Initial timing was set at 10 degrees btdc.  With the throttle cable detached, I raised the RPMs to 3000 and achieved between 26 at 28 degrees btdc.  34 degrees is expected.  The curve overall was very smooth when increasing or decreasing RPMs.  According to the manufacturer specs, this distributor is programmed for 24 degrees of total timing.  When pushed to 3500 RPMs, the total timing numbers remain the same.

DUI tech support suggested a resistance test on the pickup coil.  After disconnecting the wire connector from module under cap, the multi-meter showed 846 ohms.  800-1000 is considered acceptable.  

Maybe I am out of options.  Maybe I am making a mistake somewhere along the way.  Or maybe it's as good as it's gonna get.  The engine runs well.  It accelerates through the power range without hesitation.  I hit 4500 RPMs and 42 mph in nearly calm water.  If engine performance can be improved I am eager to learn from the members.