Another tid bit . The WORST injectors that need servicing more times than not, seems to come from Florida, Michigan and Arizona. I actually get injectors from all over the USA and even Canada

2 very hot states all year round - one very humid and one very dry but super hot and one very cold state - long lay up winter timeframes.

I do notice this of the injectors - Michigan gasoline smells way different than any other state in the USA..

Next is, it seems Canada gas blends seem to stay cleaner longer as well. This is what I noticed testing fuel injectors and the different smell of the fuels

i don,t know anything about the smell of canadian gas but i kind of noticed that some of the people from canada smell,well kind of like dead fish!

All of what you said is good and true, but if you run wide band full time it becomes a moot point. In other words keep your AFR in line and things will be OK. From my experience worrying about injector voltage bias (which is even in MEFI 1 tables) and dead band is over kill. Tune to the correct AFR and monitor and you will be fine. I'd monitor AFR on a carb motor.

To reiterate I do not disagree with your technical analysis.

Yes, thats why i mention self tuning efi and full time tail pipe o2 meters and if available use injector charteristics of new injectors to set injector voltage bias, makes tunning much easier!

Tuning is not for the novice or the do it yourselfer I will add. For a jist of info - first on the dyno it is best to tune with one wide band for each cylinder to dial AFR's in correctly. Then a final dial in tune out on the water where most of your boating takes place. Keep in mind one wide band per bank only gives you an average of that bank across the board - so you can have some cylinders lean and some rich, the average of that is taken. All can look great for AFR 's but it is not per each cylinder. Just adding IMO how it really should be done. I know that is how we are doing my stuff on stand alone ECM's and I would not want it any other way period. And I am not too proud to admit, I will have way more expert hands helping me in person as well with complete tuning from start to end.

Anyways these 500 EFI's Multecs have been shipped - a bit of info, 5 of these injectors I would not have used in a lawn mower period. More info to come. when I have time to write more what I did on my end before shipment. I want to have the direct replacement for these. I strongly suggest to replace / upgrade the Multecs in the 500 EFI stock apps. Not a sales pitch but I am telling all straight up. I am just passing on solid info here.

We have been cleaning and flow testing injectors for about 8 years also and i agree that the 500 efi injectors are junk when they get old the magnets get weak and will cut off flow,i have seen them shut off as low as 40psi,i have sent them out to several experts to find an exact replacement with no luck you can buy them from gm as they are the ones they use in there crate 502-500 but they are still around 200 per injector.the 525 injector is a 50lb and is a lot better injector,i agree if you try to just install the same lb per hour injector you will need to re-tune too many factors,it would be nice to find an exact replacement not many people can handle spending 1600 for a set of injectors,maybe someone could sell a ref lash and replacement injectors probably too much liability to be worth it

MDG. So are you saying the GM injectors being used in the 502-500 crate motors are replacements for the mercury 500 efi are not? Because right about now I am looking for replacement injectors and $200 injector is not going to be an issue when I hear boats running up and down the bay and mine is sitting in the shop with bad injectors. And frankly with having all my time and money wrapped up in these two complete rebuilt motors I am open to all ideas.

If yours have Delphi # 17090304 printed on the injector they should be GM# 17090919

16 different injectors have been tested up to this point - nothing so far is a perfect match for a stock calibrated ECM... Each time 3 new injectors are bought comes out of the pocket here so with said 16 x 3 = 48 injectors bought wholesale for testing to find a current offering.to match. Again so far nothing matching perfectly for a stock tuned ECM. . NOT CHEAP buying these trying to find the perfect match for the Multec's. with that said it is done at a lot slower pace for testing because of the cost involved.. The pace could move very fast if I found an endless supply of money.

Also keep in mind installed height needs to match as well. .

This is the only news I have to date. We will continue the testing process as all the dated has been tested and recorded from the Multec's.

GM does not support these period nor the GM 17090919 - they are NLA as OEM GM injectors but are made from RAM JET. knock off injectors that is not a quality made.