Go Back  Offshoreonly.com > Technical > General Q & A
Dennis Moore, John B, and the HP500 EFI >

Dennis Moore, John B, and the HP500 EFI

Notices

Dennis Moore, John B, and the HP500 EFI

Old 09-22-2003, 02:47 PM
  #21  
Registered
 
jdnca1's Avatar
 
Join Date: Feb 2002
Location: KY
Posts: 1,099
Likes: 0
Received 0 Likes on 0 Posts
Default

My 500EFI's run better on 87 than 93. Also cleaner with lower octane.

JohnB your plugs definately look fat from the other post, but I'm scratcing my head as well after looking at your EGT's.

Maybe the MR43T plugs are not ideal, too cold....??

I have a 632" in my other boat that makes 900HP on pump gas (tunnel ram) and the plugs look perfect. Didn't even have to really work at it. EGT's around 1300 on the dyno.
Run NGK plugs in this motor, the -10's were a little on the fat side and I switched to the -9's (1 step hotter) and they have the nice dark brown color. -8's were a little to scary looking to me (a trace of aluminum specs on the porcelin)

I may try to cross the MR43T's with NGK and play with the heat ranges.

Last edited by jdnca1; 09-22-2003 at 02:51 PM.
jdnca1 is offline  
Old 09-22-2003, 03:26 PM
  #22  
Adivanman
Guest
 
Posts: n/a
Default The Lean / Rich Thing.....

Over the course of this and JohnB's previous post, there have been a couple of references to the richness of the HP500 EFI, a "sooty" transom, and blackened spark plugs. None of these are new topics to HP500 EFI owners but they are worth discussing....

The rich/lean thing...

At WOT the HP500 EFI is running slightly lean - no question. Throughout most of the camshaft powerband the HP500 EFI is running slightly (and I would argue acceptably) rich. At idle and below the camshafts powerband, the HP500 EFI seems rich when cold. This is not a shortcoming of the engine, rather it is an attempt to build a Race engine that can survive in a pleasure boating environment. The engine was not designed nor intended for extended use "off" the camshaft. No high performance or race engine - marine or automotive - carburated or injected - can be all things to every one, all the time.

The sooty transom thing...

First and foremost - soot does not equal rich by default. By definition, richness is the state in which more fuel is entering the combustion chamber than can be burnt in a single ignition event. The end result of "rich" is raw, unburnt fuel in the exhaust, a condition often associated with burning eyes, stinking exhaust, and yellow film. Soot is the end result of combustion.

Many boats with HP500 EFI's experience sooty transom conditions not due to the tuning of the engine, rather, due to the lack of tuning of the exhaust (and transom backwash). In my experience, most boats with "sooty" transoms (regardless of engine) have (a) larger "lopey" camshafts, (b) some form of switchable exhaust, and (c) exhaust in which the water mixes directly with the exhaust gases well forward of the tip - these conditions are met by most boats running with the HP500 EFI. In these circumstances soot not only freely mixes with water but does so in a relatively "slow" exhaust stream. When the exhaust gases (and liquids) exit the tail pipe, they do so only inches above the water or in aerodynamic vortex beneath the swim platform.

Is it more common at low speeds than high speeds? Yes. Lower exhaust velocity and you are not utilizing the camshaft. Is it more common with high octane than low octane? Yes. Besides octane, the different grades have different specific gravities, etc. Does the exhaust system make that big a difference? Yes. We changed from a "factory" system with Corsa Q&Q and went to a true water jacketed exhaust and have not cleaned the transom since.

I have also had the opportunity to run the HP500 EFI in a truly dry exhaust, both with and without backpressure. I can tell you without a doubt that the engine prefers no back pressure.

The spark plug thing...

Does not have to have anything to do with the first two points. It is not fair to draw conclusions (about the engine) based upon pictures of one set of plugs and no background. There are many possible factors that could and may be in play here - maintenance being first and foremost. Air Cleaner? Cap, Rotor, and Plug Wires? How old are the plugs? Who put them in and how? After maintenance is history. With a conventional ignition, generally speaking, once you severely foul a plug you will not clean it up again - ever. A service event in the past may have left fouled plugs today. Are these engines new or rebuilt? Finally there are the wildcards - operation and contamination. Simply not enough information.

Adivanman
 
Old 09-22-2003, 04:02 PM
  #23  
MAG502NUM
Guest
 
Posts: n/a
Default

I once inquired with Arizona Speed & Marine on their EFI setup for my 502 and they reccomended a cam with a intake lobe in the low to mid 220's @ .050 as optimum and that when you go bigger on cam timing it just start contridicting[higher RPM] the long runners on the manifold!!! This in itself is no biggie except when you consider that they are the manufacturers of the setup Merc uses on the HP500EFI!!Merc goes 230 degrees on the intake lobe...FYI

Dont shoot the messenger...just repeating what I was told.

Last edited by MAG502NUM; 09-22-2003 at 04:16 PM.
 
Old 09-22-2003, 04:52 PM
  #24  
Registered
 
jdnca1's Avatar
 
Join Date: Feb 2002
Location: KY
Posts: 1,099
Likes: 0
Received 0 Likes on 0 Posts
Default

500 EFI Cam specs;

211/[email protected] .582"lift CL not given
jdnca1 is offline  
Old 09-22-2003, 05:11 PM
  #25  
Adivanman
Guest
 
Posts: n/a
Default

jdnca1,
I have to admit, you are beging to lose me here with your information. Are you sure that you are looking at HP500 EFI data?

For the record:

HP500 EFI Cam Specs:

Crane Part Number #169621.

292/298 Duration @ .004
230/236 Duration @ .050
.598"/.610" Lift
114 Lobe Center.

Last edited by Adivanman; 09-22-2003 at 05:16 PM.
 
Old 09-22-2003, 07:22 PM
  #26  
Registered
 
jdnca1's Avatar
 
Join Date: Feb 2002
Location: KY
Posts: 1,099
Likes: 0
Received 0 Likes on 0 Posts
Default

Adivanman;

I have Mercury Racing's service manual#6

PN 90-840283R01

GM 500 EFI Engine, Dated October 2002

On page3A-6 it shows a bore of 113.5 (4.5), however as shown further dowen the page the actual bore is 4.466. So they did round up.

On page3A-10 they show lobe lift @.020 (.342)

Duration @.050 of 211 / 227

I was surprised at cam being that short, its hard to believe....maybe book is wrong??

Still looking for rev limit info.
jdnca1 is offline  
Old 09-22-2003, 08:00 PM
  #27  
Registered
 
Join Date: Oct 2000
Location: Spicewood, Texas USA
Posts: 1,382
Likes: 0
Received 3 Likes on 2 Posts
Default

jdnca1, seems like I just got a Merc service bulletin correcting the book. Those numbers are not right. I'll try to remember to check at the shop tomorrow.

Bob
bobl is offline  
Old 09-22-2003, 08:22 PM
  #28  
Registered
 
John B's Avatar
 
Join Date: May 2001
Location: Amherst,NY
Posts: 520
Likes: 0
Received 2 Likes on 2 Posts
Default

Adivanman,

Very through explanation, it has merit. Would this exhaust situation also cause the engine oil to turn black after 5 or 10 hours? Or would this be caused by (running off the cam)?

Maybe it is also rich somewhere. How does it run in the car? Did you try it in its stock form? This would be interesting.

What do you think the best heat range plug would be?

Also, do you have any thoughts on the spark curve? Some times I get hung right at 5000.
http://www.offshoreonly.com/forums/s...threadid=34010

Thanks, John B
John B is offline  
Old 09-22-2003, 08:56 PM
  #29  
Registered
 
jdnca1's Avatar
 
Join Date: Feb 2002
Location: KY
Posts: 1,099
Likes: 0
Received 0 Likes on 0 Posts
Default

Bobl;

Thanks for clearing that up;

Adivanman;

your specs are much closer to what I would have expected.

Have you found any larger cams that work well with the 500EFI? Reprogram ECU to compensate? I was thinking something like the Crane 741 and taking limiter to 5800 with lifter and valve spring change.

thx in advance.

Corey
jdnca1 is offline  
Old 09-22-2003, 10:05 PM
  #30  
220BR
Guest
 
Posts: n/a
Default

BTY, where is his reply to Adivanman question???
You gotta be sh*tting me! Respond to you bunch of little old ladies sitting around tying your panties in a knot. Not likely
 

Quick Reply: Dennis Moore, John B, and the HP500 EFI


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.