PCM 351 Vapor Lock Issues

[Supra_Comp]

I just watched your videos, I wish I had watched your thread….you had the exact same problem as me! When yours started acting up I immediately knew.

Lively, great information. Well done sir. I bought a new coil and matching ballast resistor tonight (actually got an MSD from my local store because it was what they carried) and it is a .7 ohm to be used with the resistor.

I will wire mine up tonight (basically just switching wires around) and provide an update!!

[Supra_Comp]

Wired it tonight, and did a quick dry start and it fired immediately...hasn't done that in many years! With no pumps. Shut it down though, I drained the fuel separator during my investigations so I'd rather have it hooked up to water.

So far so good. Taking it to the lake on Saturday for a trial run!

[lively]

Make sure timing is correct as well , I run 8 degrees BTDC , others here will run 10 degrees BTDC . And once you start it on the water let it warm up and then just briefly touch the resistor to check for warmth . If it's hot you know it's working ! Good luck and let us know how it turns out !


Sent from my iPhone using Tapatalk

[Supra_Comp]

Well guys, I think we have success. *knock on wood*

Dropped the boat in the water and it runs incredible. Fired it up and immediately checked voltage at the + of coil and saw anywhere from 9.3 to 9.7 volts. Ballast resistor was hot and the coil was relatively warm/hot but not scorching. Drove out of the harbor and gave a few pulls from a idle...I can easily say I have never felt the boat move that quickly from a hole shot before!

The other thing I did notice was the reliability. I did about 10 hole shots and not once did it hesitate or stumble. It also pulls harder once up on plane too, honestly never gave it more than 1/2 to get on plane and the throttle response while cruising was very crisp. Even after getting back to the dock and letting it sit, it fires right up with out any stumbling.


Would just like to say thanks to all you guys for your help!

[lively]

Your voltage is spot on and as long as the resistor is hot it's working . Glad to help and enjoy


Sent from my iPhone using Tapatalk

[Supra_Comp]

Had the boat out this week and it ran fantastic! Great throttle response and never gave out on my once. Pulls me (215 lbs) on a slalom from a deep start with ease.

Since I had some flat conditions, I thought I would give it a full out run. When giving it full throttle and going for max speed, at around 35-37 mph I get a bit of a hesitation (when the vacuum secondaries open up) for a second and then it kicks back in and I am able to get it up to about 40-41 mph (roughly, speedo's aren't perfect). My assumption here is a lack of fuel and some minor carb tuning. Has anyone found a good combination of pump cam and vacuum spring?. Still the stock 4160 carb.

Other than that, we are running good!

[lively]

Check timing and set 10* BTDC , full advance at 3600 rpm should be 32*-36* degrees , hesitation could be from bowls running dry . Adjust float levels .

[cadunkle]

You may also try a stiffer secondary diaphragm spring. No accelerator pump on secondary side so if they open too quickly it'll cause a lean stumble on the transition. Failing that you may try going up 2-4 jet sizes on the secondary side. If this is a 4160 your options are more limited and you'll need a different metering plate or to enlarge the holes in yours slightly (not reversible). You may try slightly raising the float level on the secondary side as this will slightly richen the mixture. going richer will not likely cure a lean stumble from secondaries opening too quickly though.

Retarded timing or late/jerky advance will also cause a stumble.

[covertcombatant]

Is there any coil that you can pick up from napa / autozone / oreilly that will work?
My coil is the same as the one on skidim R117001and it has the prestolite electronic conversion without a resistor. Would like to pick one up before I put it on the water tomorrow.
Thanks.

[Supra_Comp]

Here is what I am running, you should be able to get it at most stores.

http://www.msdperformance.com/Produc..._Hardware.aspx

Notice that it has 0.7 ohms resistance on the primary where as the one you are running has 1.5 ohms. I switched to the lower resistance and ballast resistor as I was having issues at operating temp. Just be sure to find out what works best with the prestolite conversion.