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  Sportjet 175 Rage dies above 1200 RPM's - HELP!

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Author Topic:   Sportjet 175 Rage dies above 1200 RPM's - HELP!
diveguy posted 06-19-2004 03:24 AM ET (US)   Profile for diveguy   Send Email to diveguy  
I have a 1997 Mercury Sportjet 175 in my Boston Whaler Rage. The V-6 gas motor has less than 50 hours on it, and it's run flawlessly up to this point. The engine serial number is 0E263389.
About a month ago, after being on the water for several hours, the engine stalled out like it was running out of fuel. It still had 1/2 tank or so of gas, but I switched over to the reserve anyway, to no avail. The engine barely ran, and I limped it back home at 1200 RPM's - the most I could get out of it. It acted like I had run out of fuel - 1200 rpm (or so) max, sputtering a bit, with no accelleration. It died several times and was difficult to start.
I took the boat to my local shop, and they first tested the ignition, and said it tested fine. The engine compression was at spec, and it seemed obvious it was a fuel delivery problem.
The shop checked the tank, lines, check valves, and entire fuel system. They ultimately replaced the electric fuel primer pump, a check valve,  fuel lines, rebuilt the vacuum-operated fuel pump, cleaned out all 3 carbs, and made sure there was no air in the lines.They said the reed valves looked fine. Then I took the boat home to test it.
It still will start ok, but when I give it gas, it still falls flat on it's face, stalling out and nearly dying. It won't get above 1500 rpm's or so. If I suddenly accellerate, it will get up to 3,000 rpm's for a few seconds, then die. It still acts like it's running out of fuel. But how?
The shop has 20+ hours into this, and they have no idea what's wrong. After all this work, it's still the same as when it first died on me. The shop called Mercury Tech, who is the one who suggested rebuilding the fuel pump, which they did. The boat has been out of the water for 4 weeks, in the shop for 2+ weeks, with no solution in sight.
Any ideas? I'd like to get my boat back in the water now that summer is here, and with no ideas as to what this could be, we have no idea on how to proceed.
Any advice would be sincerely apprecitated!
Clark Roberts posted 06-19-2004 07:54 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Dive, check and see if your fuel tank has a check valve near the pick-up tube (sometimes cleverly hidden in a barb fitting). These nasty little spring-loaded things can stick and no amount of fuel pump rebuilding will supply enough suction to operate the engine... check it out and if there is one...REMOVE IT .... Happy Whalin'.. Clark.. Spruce Creek Navy
diveguy posted 06-19-2004 01:14 PM ET (US)     Profile for diveguy  Send Email to diveguy     
The check valve was replaced by the service shop, and the problem persists when an external tank is used to bypass the main tank.

From what I've learned, I'm starting to wonder if it's the stator. They said their computer says it's fine, but the symptoms seem consistent with a bad one, and we've gone through the entire fuel system to no avail (new lines, primer pump, rebuilt vacuum fuel pump, cleaned carbs.)

Something I noticed yesterday when testing the boat in the water - I don't know how relative this is. When cold, I made it out of the harbor area at probably 1800 rpm's or so (didn't note the speed or rpm's though). It ran fine, then when the motor was all warmed up, it died when given throtle, and barely limped back to the dock - running noticeable worse after warming up.

Again, any ideas appreciated!

tuna1 posted 06-20-2004 01:29 AM ET (US)     Profile for tuna1  Send Email to tuna1     
Hi diveguy
Your problem is 1 or more of the hall effect sensors in the high speed side of the Trigger Plate Assembley is sensitive to heat.When it gets heated to a certain temperature it goes out and does not fire the capacitor discharge ignition system.

The Mercury CDI ignition system uses a low speed pickup and a high speed pickup for their ignition systems.The low speed pickup handle idle to approximately 2500 RPM.The high speed pickup handles from 2000 to maximum RPM the powerhead can achieve.

The Trigger Plate Assemble is part # 96455a15 list price is $65.05.Any further questions is best asked/answered over at SportJet World(where you have priviously posted),Rages not accepted here very well.....

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