Struggling with a 502 MAG with side mount whipple the engine does not idle reliably it dies when trying to go in and out of gear at an idle making navigating the docks very difficult, I also have a bad dead spot just off idle where the engine falls on its face when trying to accelerate. You can get past this by playing with the throttle once it clears and catches the engine runs very strong.
I have scoured the forums I have found multiple forms that talk about the TPS and IAC on naturally aspirated motors but none or very little about it with a supercharger. The engine is a fresh rebuild with only a couple hours on it but this problem existed before the rebuild.

• Also one thing worth noting is that the IAC is mounted in the adaptor plate between the whipple and the throttle body not in its stock location.
• When the engine was rebuilt the aux injectors and Whipple ecm were removed and new injectors, fuel pump, and tune were installed.
• The engine dyno'd at 621 HP / 758 TQ
• The IAC is brand new.

I do not have access to a DDT or scanner, so any help would be greatly appreciated. I found one thread that detailed checking the IAC and TPS voltages with a DVOM but it did not provide which pins to monitor while adjusting the throttle plates for this it was also on a naturally aspirated engine in stock configuration.

TIA

I'll start by saying I AM NOT a mechanic...I did have a 502 side mount whipple several years ago that I fought constantly near the end it suffered from the same problems you are describing. The guy that bought the boat was a mechanic and he finally found numerous vacuum leaks which were causing the problem. After that he said it ran great until a few months later when the whipple computer went bad and leaned out the fuel supply and that put an end to the motor.

I had the same problem with the Whipple computer that is the reason it was just rebuilt, But the idling symptoms are the same as before. I cannot find the installation manual from the Side mount whipple to verify all the hose routings the only documentation I can find is for the newer top mount Whipple.

My buddy has a side mount whipple on his 502 mag in a Nordic rage...anyway right after he bought the boat it ran very bad...back firing would NOT idle would die when trying to give it gas....ended up just being a good old fashioned tune up fixed his problem...cap, rotor, plugs, and wires...runs like a top now

Mine is in a RAGE as well, I do not have any back firing just a stumble right off idle and issues trying with it staying running at an idle.
I found a manual for a top mount whipple with the adjustment procedure for the IAC and TPS I am going to attempt to follow it as best as I can to confim voltages and counts for the sensors this weekend but it will be a struggle without a scanner to ensure it is correct and ensure the problems is not somewhere else.

Im tuning 2 of these on dyno, without having the ability to see iac counts, spark stabilization, droop, timing down low etc i cant imagine trying to get one to run right. Take whole boat to a tuner or buy a tuning program if you feel like tackling it.
Set iac to minimum counts you can get away with at hot idle so it has as much range as possible would be a good start. On dyno i seen rich afr actually made this blower surge and unstable too, again, your going to need to see information and make appropriate changes, Smitty

+1 to BBYSTWY

By deductive reasoning I figured since the issues were similar to the symptoms it had before the engine rebuild I assumed it had to be something still on the engine. That being said I ordered a pile of parts for the ignition system as well as a new TPS. At the same time I bid a Rinda Tech Mate on Ebay. So Friday evening I installed all parts not having a lot of confidence that swapping the parts would make a big difference. But when I fired it up on the hose in the driveway the damn thing ran good, No dead spot and it did not stall out when dropping the throttle quickly.
The throttle does hunt around a little bit when it hits bottom before leveling but I'm sure that is just an adjustment with the IAC and TPS that I will be able to clear up as soon as the Tech Mate arrives.
I do not know what the exact culprit of my issue was because I replaced all parts at the same time but something involved made a big difference. CAP, ROTOR, PLUG WIRES, IGNITION MODULE, TPS.
Once I receive the Tech Mate to fine tune the IAC, TPS, and get a chance to put it on the water I will follow up with the results.

While the scan tool will be a nice addition, it will not let you do any tuning. It will only read what the sensors are doing. To change anything, you are going to need MEFI Burn or similar software.

I don't believe any tuning will be necessary, I am confident my issue was component failure. Being able to read the TPS and IAC I will be able to adjust the set screws behind the individual throttle plates to line out the TPS idle voltage and the IAC counts.
I will admit that early when this started I messed with them to see if it made a change but returned them to what I thought was the starting points when it did not. Now with the scanner I will be able to set them where they should be and not have to guess.

I bought a used boat with side mount...rich idle condition...found major vacuum leaks left from previous owner....capped them...now better than ever