502 Mag (Carb.) concerns or upgrades?
04-18-2004, 07:10 AM
#12
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Originally posted by mcollinstn
Leave your 20 degree module in there and bump to 10. Give it a try and if you are good, then go to 12. It's free.
My 502 carbs like 10 degrees on 87 octane.
Leave your 20 degree module in there and bump to 10. Give it a try and if you are good, then go to 12. It's free.
My 502 carbs like 10 degrees on 87 octane.
marine manifolds and I,ve got my props being labbed
at Houston propeller. Do you think better flame
arresters would make any difference?
04-18-2004, 09:40 PM
#13
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flame arrestors?
My gut feeling is that they won't make any noticeable difference. It is awful easy to test, though.
Roll up a bunch of towels or get a 6 pack cooler or something to close your engine hatch on top of that will keep the lid open 6" or so.
Get a friend to ride with you. Have him sit on the backj seat. Go do a baseline WOT run at full operating temp. Note GPS speed and rpm. Drive back to the same spot. Yank the arrestors off and have you friend hold a fire extinguisher. Repeat the baseline run.
If you see an increase in performance, you WILL benefit from a better designed flame arrestor.
Cheap easy effective test.
(I've tried it. No change. Doesn't mean that it will turn out the same on your boat.)
My gut feeling is that they won't make any noticeable difference. It is awful easy to test, though.
Roll up a bunch of towels or get a 6 pack cooler or something to close your engine hatch on top of that will keep the lid open 6" or so.
Get a friend to ride with you. Have him sit on the backj seat. Go do a baseline WOT run at full operating temp. Note GPS speed and rpm. Drive back to the same spot. Yank the arrestors off and have you friend hold a fire extinguisher. Repeat the baseline run.
If you see an increase in performance, you WILL benefit from a better designed flame arrestor.
Cheap easy effective test.
(I've tried it. No change. Doesn't mean that it will turn out the same on your boat.)
04-18-2004, 09:50 PM
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Originally posted by Dennis Moore
For some reason, Mercruiser put a very slow ignition curve into the TB IV 502 carb. distributors. That would be the first place to go to increase performance. A large performance increase will come from switching camshafts to the new GM 502/502 cam and some good exhaust manifolds like the Gil. Install some RV15YC4 Champion spark plugs gapped at .045 inches and a K+N marine flame arrestor.
Good Luck
Sincerely
Dennis Moore
For some reason, Mercruiser put a very slow ignition curve into the TB IV 502 carb. distributors. That would be the first place to go to increase performance. A large performance increase will come from switching camshafts to the new GM 502/502 cam and some good exhaust manifolds like the Gil. Install some RV15YC4 Champion spark plugs gapped at .045 inches and a K+N marine flame arrestor.
Good Luck
Sincerely
Dennis Moore
but I didn't think that on stock 502's there would be
any noticeable difference either. I just cant imagine
that air intake would be a problem,as the stock
units appear to be adequate.
09-14-2004, 04:22 PM
#15
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Re: 502 Mag (Carb.) concerns or upgrades?
What octane is recommended in the 1993 502 mag (carb)??
I always thought 87 is what they always said but someone lately said this motor called for 93 octane??
The boat was a repo, so at first I ran a couple of tanks of 93 octane thru the motors to make sure I got out whatever was left in the tank!!
Since the start of this post I have completely redone the interior and painted the boat, got done in time for the 4th of July and have been enjoying the boat since then. Now is time to focus a little more on performance. I did change the exhaust to new Revolution Marine manifolds, new plugs, and changed the oil a couple of times, but that is about it so far. The best so far is 60.5 mph (GPS) light on fuel and on a cool day. at 4700rpm. the boat has 1.36 drives and is turning 19 pitch 3 blase mirages. and runs 59.5mph most generally with all of oue stuff in the boat
I hope Dennis is still around here to give his advise, I have two of his books and think it is awesome to be able to post here and get such great advise from him and others!!
Idealy I would like to pull 5000rpm (or at least get closer to the rev. limiter) and get a little more speed!!
I always thought 87 is what they always said but someone lately said this motor called for 93 octane??
The boat was a repo, so at first I ran a couple of tanks of 93 octane thru the motors to make sure I got out whatever was left in the tank!!
Since the start of this post I have completely redone the interior and painted the boat, got done in time for the 4th of July and have been enjoying the boat since then. Now is time to focus a little more on performance. I did change the exhaust to new Revolution Marine manifolds, new plugs, and changed the oil a couple of times, but that is about it so far. The best so far is 60.5 mph (GPS) light on fuel and on a cool day. at 4700rpm. the boat has 1.36 drives and is turning 19 pitch 3 blase mirages. and runs 59.5mph most generally with all of oue stuff in the boat
I hope Dennis is still around here to give his advise, I have two of his books and think it is awesome to be able to post here and get such great advise from him and others!!
Idealy I would like to pull 5000rpm (or at least get closer to the rev. limiter) and get a little more speed!!
09-14-2004, 05:19 PM
#16
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Re: 502 Mag (Carb.) concerns or upgrades?
87 octane is all thats needed.
Saw your boat when we we're at the shootout,
looks good.
I would try 1.5:1 ratio drives, and prop accordingly,
for starts.
jt
Saw your boat when we we're at the shootout,
looks good.
I would try 1.5:1 ratio drives, and prop accordingly,
for starts.
jt
09-15-2004, 09:27 AM
#17
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Thread Starter
Re: 502 Mag (Carb.) concerns or upgrades?
Thanks!! Were you the one that they said was sponsered by OffShore Only on the radio?? If so I saw you boat a couple of times and it looked like it was kicking butt!!
09-15-2004, 12:27 PM
#18
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Re: 502 Mag (Carb.) concerns or upgrades?
Originally Posted by FunHome
Thanks!! Were you the one that they said was sponsered by OffShore Only on the radio?? If so I saw you boat a couple of times and it looked like it was kicking butt!!
That was us
