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T-REX
04-20-2001, 06:46 AM
Would like sum Ideas on the pain in the but motor...One trip down the river, the motor will turn 8000rpm, make 3 passes at WOT and it may drop off to 7200, even down to 6200...Motor has A-5 box(new), new regulator, new injectors, new coils, good leakdown & compression, changed Flywheel, new plugs(resistor 9-hs-10), new trigger and Stator...the motor iz on a LTV, total weight 1250#(with motor and driver) and running a 26 yamaha wheel...I think the motor should see way more than 8000 mustless 6200...Need sum Ideas...PLEAZE T-REX

Greg Moss
04-20-2001, 07:15 AM
Rex what is the condition of the battery? is the charging circuit putting out right? I have seen the 260 loose power after running because the charging curcuits cann't keep up with the pump and fuel injection. With a good battery they ussually last longer than 3 passes though. Do you have a fual pressure gauge and volt meter on it? if not you might want to try that to see what it's doing. Hope this helps. Greg

myron
04-20-2001, 07:25 AM
Hey Rex, check all of your coils and their grounds, a cracked coil will do what you are talking about whrt it gets hot it opens up and grounds out, I have seen this many times

ChrisH
04-20-2001, 08:09 AM
T-Rex, I've heard of guys having trouble with the A-5 box when using non-supressor type plugs. The NGK BUZHW plugs are expensive, but they don't interfere with the ECUs' operation. Baker had a drag motor (A6 ECU) that wouldn't turn up until he changed the plugs.

RocketMan
04-20-2001, 08:40 AM
Rex,

I know you race and have probably eliminated all the basics, but here are some random ideas:

1) Double check battery voltage. EFI's won't run with a bad/weak/"sometimes" battery. This can be the problem when the motor starts out strong off the trailer and each run gets progressively worse. Trim pump sucks down voltage as you run boat and motor sees lower and lower fuel pressure.

2) Double check fuel pump. If pump is old and tired, sometimes they can raise hell with fuel pressure and drive you nuts. I am assuming good fuel system: tank > Merc water seperater > EFI fuel pump > Merc/Kinsler in-line filter > Motor > return line unrestricted back to top of tank and TANK PROPERLY VENTED. No automotive type fuel filters causing a restriction.

3) You say your running an A5 box? Are you talking about the ECU? Do you mean A15 or is there really something called an A5? What ever, the ECU should be matched to the correct fuel pump and regulator. I've seen guys try to run an old 39 psi fuel pump with the new 56 psi regulator (black) and A63 or A6 ECU and it doesn't work so very good all the time.

4) If all else fails change the switch boxes and especially the Black and White bias wire between the switch boxes. I had a mod-VP Merc once that drove me nuts with "sometimes" switch boxes. The motor would drop 1000-1500 RPM at times. However, it would usually start off slow off the trailer and if you got it hot enough the switch boxes would "get all better" and the RPM would jump up like a nitrous shot. Cool the motor off and problem was back.

5) Screw a new set of NGK "BUHW" plugs in it for a test or forever. EFI's, even with Digital ECU's, can run BUHW plugs. Non-resitor plugs (like BUHW) just annoy the hell out of the ECU test sets, they are fine at all other times.

Happy hunting,

Paul

jimmyb
04-20-2001, 10:04 AM
definately check the fuel pressure!

MirageMark
04-20-2001, 02:12 PM
Hey TREX, alot of good things have been mentioned here, but don't forget to check your ignition/Key switch. Sometimes a bad Key harness can really drop your RPM's due to loss of proper voltage. Good Luck, can't wait for the race in West Lake. It's the closes one to me and I wouldn't miss it for anything!!!!! I'll have to drop by and say hello.... Mark Screen

Jeff B
04-20-2001, 10:32 PM
Get some NGK (R) BUZHW plugs!!! I run a A-5 that requires a 39 pound fuel regulator. I ran BUHW plugs for around a year with NO trouble. One day it just lost power and then would not even get on plane! I took it to a Merc Hi-performance dealer where he tested Everything, and everything checked out fine. He put a A-6 with a 56 pound regulator on it and it ran fine. We decided it had to be the A-5 even though it passed all the test. Sent it to Merc, they tested it and said nothing was wrong with it,then they lost it for almost four months! They sent me a new one, It would get on plane just fine and seemed to run fine. I was running along right around the 100MPH mark and the motor DIED! After that the performcnae would come and go and sometimes it would just die. I bought the ECU from Tony Reynolds, Tony was at the lake the first time I ran it. He worked on it for a day and a half, running test, and test running it at the lake. He put some BUZHW in it and we took it to the lake, it run great and has run great ever since until today, but that is another story. Try the diffrent plugs, they are high, but it may fix it! If memory serves me right a stock A-5 has a rev limiter of 8250. The A-5 is a offshore race box that is fatter in the mid range than a A-6.