941

This is my first boat! My wife got it for me last Christmas so last season was my first time running this or any boat... The idle was not confidence building when trying to dock so I decided to look into it and have a look at what's going on in the engine bay. I know my way around an engine so why not take a swing at it?? So I found a modded 502 lower manifold on this site and got the wrenches out. Everything went smooth till it came time to get her running, need a scan tool to set tps and iac count. turns out a buddy's friend has just that tool. I find out my tps is not returning to the same number every time. I went with the Holley EFI tps and boom returns to the .47v every time. now I sweep the throttle to wot. To my surprise it was only going to 78.5%! I see Youngs performance is the go to guys with this setup so I call them. They were very nice and helpful and they told me that the tps needs to see 99.1% or better. The man I was speaking to was so nice and helpful it was refreshing, here I am asking him for information on how to work on my boat and taking time away from him billing for his time. Big thanks.



So I take off the throttle body and start looking at it. I see the linkage can be set two ways. The way it was setup, both blades open at same time which would make it fall on its face. the other way lets the first blade opens a40% then opens the second blade. this tb is so big there is no way this engine needs all the air it can deliver.




Bill added for size reference.


So after playing with the tb for a while I got it all squared away and now it get over the 99.1% at wot. Does anyone know what throttle body this is?

Tim

Trash

I can't comment on that throttle body specifically, but the factory 2 stage TB that Merc motors of that era came with were linked progressively. In other words, the first or primary TB blade opened with throttle until around 50% TPS then the second TB blade would begin to open, usually at a much faster rate. I would hazard to guess the second way you connected the linkage would be the correct way.

941

I put the boat in the water yesterday and it was sooo lean...
I had a lambda of 1.14 getting on it. All I did was fix the 78.5 wide open throttle (now 99.6) and change the intake manifold to a modded lower I bought here on this site. It must make a huge difference on a boosted motor. So I called Young performance back up... I was told to add two 80# injectors to the TB and how to run the fuel system. So this morning I got the trailer and pulled the boat out and got to it!!! next daying the ecu to Young's tomorrow!! Pics of course or it did not happen..





Tim

Padraig

Eddie is a great guy.... He will take care of you.

Padraig

bigredbaja

I had the same 502/side mount set up several years ago and mine was a disaster when I bought the boat I took it to Eddie and he fixed all the issues, if you are taking your boat to Eddie ask him about a return fuel line to the tank to prevent vapor locking. The first season I ran my boat it vapor locked constantly leaving us stranded for a hours on more than one occasion. Mine was a 252 Baja and when running strong it would hit low 70's on GPS. Mine also had an older MEFI computer that eventually malfunctioned on the next owner and damaged the engine.

RBeyer

Unfortunately most of these systems are advertised incorrectly. They make them seem like a simple bolt on when actually they are quite complex, as mentioned above, fuel lines, new injectors, re-flashing the ECU. and nobody says the drive wont last! Most motors will need a rebuild after a season to get the parts that can handle the additional stress. Speaking from experience and the tuition paid to learn to do it all right the first time or you may be disappointed!

941

Learned All this when I owned a car shop, Everybody wanted a bolt on turbo or supercharger kit. This engine will get dialed in and left as is. I am building a Dart tall deck for this boat, block is at machine shop now. What sub section should I post that in??


Tim

RBeyer

Sounds awesome. Hopefully you will post the progress to be followed.