There seems to be a lot of gripes of other threads lately. Why don't we put them right here. Maybe someone at the factory will see them and respond.

We can all have opinions, right or wrong. I don't think we should indulge in character assassinations. Lets just deal with the product and not shoot the messenger.

OK, I'll start.....

After 14 boats, I now have to take detergents on my 525 EFI powered boat to clean the carbon off my passangers who use the swim platform. This was also true with the 500 EFI's. This is real progress!

I think someone put a 500 EFI into a Camaro, I'll bet its a real polluter.
Lets see; 25 hrs per oil change X 60 mph = 1500 miles between changes. Now this sounds like a real winner.

High- tide,
I'm interested in how a motor which runs as rich as a 500efi Mercury would run in a car. I didn't think they have a lean cruise parameters in the programing. I would really be interested in this. What conditions trip them to lean out, vacuum?
I am trying to learn why Merc efi's are set up to run so rich.
Did you reprogram the computor for your application?

My comment was for Advianman, I thought he went a little over board on someone else's post, and his picture of the car made me curious from an engineering point of view.

This may be a better thread to discuss Mercury's technical know how. Yes, I did get a chuckle out of Moore's comment.

John B,

A couple of things you need to consider:

1. Issues with soot on your transom and swim platform have less to do with the Fuel Curve of the HP500 and 525 EFI and more to do with exhaust, fuel, and excessive idling.

2. I don't know where you get your information, but I would not go 1500 miles between oil changes in any race style engine.

3. As far as I am concerned, the combination is "a real winner" as you call it. 600+ HP, 600+ Ft.Lbs Tq, 89 octane pump gas in 100° Florida heat with the reliability and drivability of Fuel Injection. No valves to set, no carb to adjust, no timing to play with...in fact, outside of fuel and oil, the HP500 EFI has been zero maintenance.

4. The HP500 EFI does not run rich. If anything, at WOT the engine is borderline lean.

5. I have no need to for a "lean cruise" parameter but I can tell you that pressure will richen them up nicely.

6. I did reprogram the ECU to my specifications however I did not reduce fuel flow. The changes I made were to improve operation at higher temperatures and RPMs.

7. If you are unhappy with your HP500 of 525 EFI, perhaps you should reevaluate your needs. If you consistently operate your boats "off the camshaft" you may have more engine than you need. The blue motors were never intended to be introductory engines for pleasure boating...Mercury Racing should be a clue.

As I posted earlier, if my posts are curt (or as you say "over board") it is because I am tired of opinions being posted as facts by experts or others trying to make a profit. When I do post answers to questions, I post facts that I can back up. If I post an opinion, I will say that it is my opinion. When people in this forum post questions, they are looking for answers that they will act upon. Posts made in ignorance can and will cost people money.

Any other questions?

OK, On the serious side.

Do you have a 500efi installed in a Camaro for street use?

The 600 hp you mentioned, is this in your boat? you must have done some work to it?

I have seen some full load dyno tests on the 500's, and they have exhaust temperatures in the 1400's from 3000 rpm up. Do you think they run them rich in the mid range for this reason?

The timing curve is held at 26-28 degrees until 5000, were it then jumps to 34-35. Do you think this is for the same reason and or maybe its also to allow it to stay out of detonation with 87 octane? I know retarded timing can increase exhaust temperatures.

I am interested in whether or not they (Merc) has a different fuel program in the computer for say 3500 rpm when the boat is not floored. This would be like the power valve circuits in the carbureted models.

Maybe our questions and answers can shed some light on these concerns.
Maybe someone else also has input.

OK, On the serious side.

I thought we were on the serious side but….

Do you have a 500efi installed in a Camaro for street use?

Yes.

The 600 hp you mentioned, is this in your boat? you must have done some work to it?

The 600 HP mentioned is in the car, the boat is closer to 1800 HP.

I have seen some full load dyno tests on the 500's, and they have exhaust temperatures in the 1400's from 3000 rpm up. Do you think they run them rich in the mid range for this reason?

If you have seen the dyno tests I would assume you would have seen the A/F ratio’s as well. Generally speaking, an aspirated engine with EGT’s in the 1400’s would have an A/F ratio greater than 14:1 – not what I would call rich. Dyno sheets anyone?

The timing curve is held at 26-28 degrees until 5000, were it then jumps to 34-35. Do you think this is for the same reason and or maybe its also to allow it to stay out of detonation with 87 octane? I know retarded timing can increase exhaust temperatures.

This depends on how you time your engine. Almost all engine manufacturers arguably deliver their engines with conservative timing. They are expected to run as well at 5000 feet as they do at sea level. Besides with a DCR of 6.2 it would be hard to get the HP500 EFI to detonate with any octane of fuel.

I am interested in whether or not they (Merc) has a different fuel program in the computer for say 3500 rpm when the boat is not floored. This would be like the power valve circuits in the carbureted models.

The Alpha-N fuel injection system refers to throttle position at all times. The map coordinates are obviously different if you are throttling through 3500 or if you at WOT and accelerating through 3500.

Maybe our questions and answers can shed some light on these concerns.
Maybe someone else also has input.

Perhaps

Adivanman,

Thanks for the above information.

Check out these plugs, they have about 50 hours on them. They are out of my 36 Skater, 500 efi's, stock.
We generally cruise over 50 and get the oil temp up before running hard. They may have too many hours now, but they start to look bad after a few hours.

I'll try to send my 500 efi dyno test next, it looks lean at WOT!

Here is a close up. BTW total hours on the engines is 176. The 4 middle cylinders are oily on both motors. What do you think?

I think that they look normal for a big block marine engine. Most plugs, in a perfectly jetted big block carb engine, look like that also.

After changing thousands of plugs in marine engines over the last 30 years I have found a big difference between big blocks and small blocks. Almost all small block marine engines have perfect looking plugs when you pull them out. Never do the big block marine engines have plugs that look perfect, no matter how nice the engine is running.

Must have something to do with the larger intake ports creating lower port velocity at idle speeds crudding up the plugs.

Dennis Moore

Dyno test on 500efi with 8 hours, CMI big tube headers with pyrometers. No fuel data. It looks lean by the exhaust temps. Maybe they are richer at non WOT?

I gave up on the new scanner! Hope this is ledge able.

Dennis, I had a pair of blown 502's which we set up on a dyno for both WOT and midrange cruising. This was done with powervalves, and powervalve channel restrictions, and staggered jetting. The plugs never looked like this and its still running with 450 hours.