502 MPI Intake and Injector Question
 

So I am having my 502 worked on and the intake they have has casting number 805233C1. We are replacing it due to corrosion. The injectors that was in it are 861260T and my mechanic said someone put the wrong injectors in it. It was noticed that the injectors are too small size wise and the legs of the intake was cut down to make it fit.

After digging it seems the injectors that are suppose to go with that intake are 805225A1.

We are waiting on getting the injector in but I feel because the injectors are going to be different the fuel rail wont match. Also the spec of the injectors wont match what the computer has.

So my question is this, what is the difference between the 805225A1 and the 861260T injectors? The injector 861260T ran with that motor/computer and everything seemed fine. The issue is the manifold was modified to make fit the injector. The manifold to fit the 861260T injector is very hard to find, while a new fuel rail to fit a 805225A1 is easy to find. Should I not use the bigger 805225A1 injector?

The different injector styles use different electrical connectors and also different ECM (MEFI 1 vs 3) so they are not interchangeable without replacing a lot of other parts too. I'd suggest sticking with what you have if it works.

thanks for the reply. The injector plug looks the same on both.

My mistake. The electrical connectors changed when the 496 came out. Nevertheless, the ECMs are not interchangeable so if your current ECMs are running the mini injectors then that's probably what you should stick with.

I figured. In 1999 was the merceuiser computer smart enough to adjust to the new injectors? Anyone have experience?

The ECM's do not really adjust. They are a fixed fuel and timing map
Being a 1999, it should have an MEFI 3

No the mefi's are not self learning............reach out to Smitty ( Articfriends ) on here he's a wealth of knowledge on the 502 efi plenums and injectors, many dyno sessions

No oxygen sensor = no way at all for the ECM to see a rich or lean condition. Even if the mapping had a way to adjust based on that there is no way for the ECM to obtain that air:fuel info.

I think your mechanic may be mistaken....doing a search on the 805225A1 it looks like those are for 94-96 motors.
I think the ones you have in there now are correct for a 1999 (they fit 1998-2001...

What's your motor serial number?

The boat is a 1999. Motor suppose to be 1999. The injectors on it are injectors from 1999+ per schematic and model.
The intake is not. It is pre- 99, but someone prior to me modified it to fit the 99 injectors (smaller than the older ones that usually go into it).
seems that I need a new intake that will fit the injectors that are there (small in size). Per schematic it is 861300A2.
issue is I can’t find any and I have a new intake, but it is pre 99 and fit the bigger injectors only.

Ill grab it but I block is dated after 1999.

With intake being modified it won't matter now

How can I fit a 861260T Injector into my 805233C manifold. The 805233 Manifold takes a bigger injector (805225)

Attached is photo of the 2 injectors. The small is what I have on my motor now (861260T), the big one (805225) is what fits into the manifold I have.

https://cimg9.ibsrv.net/gimg/www.off...a634c176d4.jpg

I have a ‘98 intake as well as a better than factory set of injectors. The intake isn’t in the best of shape but it did seal well using the factory Merc gaskets. Send me a PM if interested.

would your set up work with my computer? What if the injectors are not the same as what the computer is set for?

What ecm do you have ? how was the intake modified for the smaller injector

should be MEFI-3
the studs of the intake was shaved down and injectors jellied into the hole. It worked for a season.
but now I am putting a new block into the boat and was going to change the intake to a new clean one and my mechanic saw this. Now I can’t find a intake that fits the smaller injectors.

My original 502 motor 415 HP used MEFI-1, manifold 805223 and injectors 805225 (37 psi)
The motor was repowered 530 HP using a MEFI-3 with same intake and injectors (40 psi)

Either MEFI will work just make sure the fuel tables are done correctly when re-flashing

what year was your 502?
I really don’t want to deal with flashing and keep the current injectors that are with the motor. But I can’t find a intake to fit them :(
not sure if there is a adaptor or something to make it work?
looks like these injectors fit to a intake number 861300A2

Just use the same flow rated injector the system was originally setup for assuming no fuel pressure modifications or fuel table modifications. Early small blocks typically used Kehien 26 lb/hr injectors at around 40-42 psi, big blocks stepped up the injector size to around 36-42 lb/hr at the same fuel pressure. You can get your existing injectors flow tested to see where they stand and will also tell you if they are flow balanced.

In short, IF you have say a 36 lb/hr injector, any other injector that flows 36 lb/hr will work with your system, assuming you can get the correct electrical connections and fuel rail/manifold fitting size.

thats because mercury never used the small injectors in this application, if the lb hour rating is the same on both injectors ( small & large ) buy Toms stuff and be done with it

https://www.ebay.com/itm/12367585652...3ABFBMkqiz_ppg

Don't know for sure, bought the MPI setup from a guy in NY many years ago, and the block is a Gen VI crate motor from GM at the same time.

My point is a MEFI 1 or 3 will work with the older injectors. Didn't know if you wanted to build more power or just keep it stock

I have a complete mpi set up including injectors id let go Bought it fora project and never completed it.
Has small injectors and the manifold is like new.

shoot me some photos. I messaged you.

Nice speaking to you on the phone. information for others who stumble acrossed this thread:
"early" 454/502 mpi efis used injectors that are called "honda Keihan style" they have a 11mm hole in fuel rail, no down legs on the rail and are about 2 3/4 long and the early intake used with them had a 22mm recess to seal the lower intake with a very large grommet, so a normal long style injector will not fit into the rail and would be loose with its 14mm od on bottom. strangely Mercruiser brought this EXACT injector back into service when they built the 525. It uses a EV-1 style plug and flows in the mid 40s lb wise depending if your testing with isoheptane or gasoline, 3 br pressure or less like these actually run
The later syle, mostly gen 6/mefi 3/cool fuel used a 14 mm od injector and it was about 1 3/4 long, the hole in lower intake is designed for 14mm end, not the huge grommet the early ones used. it was also rated in the mid 40s and had ev-1 connectors.
on a UN-modded 454/502 (no headers, no cam change etc) they run so rich from factory that many have swapped intakes and injectors as a whole with no issues from the slight differences in characteristics. I always recommend tuning based of tailpipe afrs if possible to be safe though, Smitty.

If you're still looking pm your phone number and Ill text you pics. Sorry I haven't been on this site since I replied and didn't see your pm.