502 Loss of Power (continued)
09-09-2002, 10:53 PM
#1
502 Loss of Power (continued)
Recap first: '92 Baja 240 502 Mag N/A, elect. fuel pump
Early July - ignition goes out, replace cap and rotor, works OK (slight power loss)
Late July - decide to go ahead and replace plugs and wires (extreme power loss) plugs were fouling bad, heavy carbon build-ups.
Early August - coil leaking cooling fluid, replace with new MSD epoxy potted coil. (still extreme power loss) At this time, found out the impeller was shredded, however never had any signs of overheating. Replace impeller and housing. Tried several suggestions from the board. 1. check plug wires, OK 2. go back to original plug wires, OK 3. go back to original prop (testing at the time), OK. STILL major power loss.
Engine starts and idles fine, but when throttling up to get on plane it just runs about 2500 rpm's and never planes out. It really bogs down once throttle is applied and just kinda hangs there. You get the picture that about half of my summer has really sucked!
OK here's the 2nd or 3rd chapter (I forget which).... Local merc tech says water in fuel, replace seperator and even open carb (Weber) and wick all the bad fuel from the bowls. Fingers crossed we try again... same thing. Idles fine just no power. I'm to the point now that I did some engine damage before finding the impeller went out. This is my last ditch effort to see if anyone here has any suggestions that I may try or at least lead the merc tech in right direction. Stick a fork in me... I'm done!
Thanks (again) for all the help up to this point!!
Travis
Early July - ignition goes out, replace cap and rotor, works OK (slight power loss)
Late July - decide to go ahead and replace plugs and wires (extreme power loss) plugs were fouling bad, heavy carbon build-ups.
Early August - coil leaking cooling fluid, replace with new MSD epoxy potted coil. (still extreme power loss) At this time, found out the impeller was shredded, however never had any signs of overheating. Replace impeller and housing. Tried several suggestions from the board. 1. check plug wires, OK 2. go back to original plug wires, OK 3. go back to original prop (testing at the time), OK. STILL major power loss.
Engine starts and idles fine, but when throttling up to get on plane it just runs about 2500 rpm's and never planes out. It really bogs down once throttle is applied and just kinda hangs there. You get the picture that about half of my summer has really sucked!
OK here's the 2nd or 3rd chapter (I forget which).... Local merc tech says water in fuel, replace seperator and even open carb (Weber) and wick all the bad fuel from the bowls. Fingers crossed we try again... same thing. Idles fine just no power. I'm to the point now that I did some engine damage before finding the impeller went out. This is my last ditch effort to see if anyone here has any suggestions that I may try or at least lead the merc tech in right direction. Stick a fork in me... I'm done!
Thanks (again) for all the help up to this point!!
Travis
09-10-2002, 01:00 AM
#3
Charter Member # 55
Charter Member
Like Playn said, first do a compression check or leak down.
Sounds like you've changed out most of the ignition. What is the timing set at and what ignition module do you have?? Probably a 24* module. Set initial at 8-10* and then check timing at 3500rpms. It should be 32-34*
After the tech said you had water in the fuel, did you drain the rest of the tank????
With the black plugs, that would indicate poor ignition or a rich fuel condition. BTW, what do you mean when you say "ignition went out" in early July??? Could the carb be leaking internally somewhere or has it been modified??? I have a stock Weber off a 454 Mag you can have for cheap if you need it.
With that power (390 hp) in that boat, you should be able to spin a 23" Mirage Plus at 5000+rpms.
First thing I would do is check timing from idle through 3500rpms and make sure its advancing properly. If it is then I would do a comp check.
Good Luck.
Sounds like you've changed out most of the ignition. What is the timing set at and what ignition module do you have?? Probably a 24* module. Set initial at 8-10* and then check timing at 3500rpms. It should be 32-34*
After the tech said you had water in the fuel, did you drain the rest of the tank????
With the black plugs, that would indicate poor ignition or a rich fuel condition. BTW, what do you mean when you say "ignition went out" in early July??? Could the carb be leaking internally somewhere or has it been modified??? I have a stock Weber off a 454 Mag you can have for cheap if you need it.
With that power (390 hp) in that boat, you should be able to spin a 23" Mirage Plus at 5000+rpms.
First thing I would do is check timing from idle through 3500rpms and make sure its advancing properly. If it is then I would do a comp check.
Good Luck.
09-10-2002, 08:01 AM
#4
Thanks Playn & Griff...
I'll start with the timing check and compression test.
Griff - When I said "the ignition went out" the engine began to miss then died and would not fire. Found out the distributor cap had some corrosion on the contacts. Replaced cap and rotor. Yeah, the black plugs caused me to chase ignition problems, then when that didn't seem to cure it, I looked to fuel delivery. And, no, I took the cheap way out and did not drain the rest of the fuel in the tank. I'm paying now.... I'll keep you in mind on the Weber carb. Per the previous owner, the carb was new about 2 1/2 years ago. Got the 23 Mirage Plus already, just haven't had a decent run with the problems I've had.
Thanks guys... keep 'em coming.
I'll start with the timing check and compression test.
Griff - When I said "the ignition went out" the engine began to miss then died and would not fire. Found out the distributor cap had some corrosion on the contacts. Replaced cap and rotor. Yeah, the black plugs caused me to chase ignition problems, then when that didn't seem to cure it, I looked to fuel delivery. And, no, I took the cheap way out and did not drain the rest of the fuel in the tank. I'm paying now.... I'll keep you in mind on the Weber carb. Per the previous owner, the carb was new about 2 1/2 years ago. Got the 23 Mirage Plus already, just haven't had a decent run with the problems I've had.
Thanks guys... keep 'em coming.
09-10-2002, 02:34 PM
#5
Charter Member #737
Charter Member
If you need someone in the area to look at it don't even bother with the shops in the KC area. Head to the Ozarks for better service and mechanics. Several people on the board us lake shores 1 573 374-5257.
09-10-2002, 05:04 PM
#7
What would cause it to not advance? Would it be the module on the exhaust riser or the smaller module in the distributor? I could replace either one myself but I'd rather not spend the $$ if it's not necessary. I've never checked timing myself and not sure where to start, besides buying a timing light. I know there's alot of OSO'ers here in KC. If anyone local could lend me a hand, I'd supply the adult beverages.
09-10-2002, 05:27 PM
#8
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The module on the exhaust riser is the ignition amplifier that has the timing advance built in. The unit in the distributor is just the magnetic pickup. There are 2 usual ways timing goes off, 1-the distributor is held in place by one bolt, it sometimes comes loose and the distributor turns retarding the timing, 2- the ignition amplifier ( on the exhaust manifold) goes bad and doesnt advance.
To check the timing advance you either need a timing light with adjustable control, or a timing tape on the harmonic balancer. You have to hook it up, start the engine, check idle timing and then run it up to 3500-4000 and check to see if its has advanced. Usually somewhere between 34-36 degrees advanced.
As a start, I would grab the distributor (with the engine off) and see if you can turn it by hand, if not, borrow an ignition module from somebody and try it first before you buy one.
To check the timing advance you either need a timing light with adjustable control, or a timing tape on the harmonic balancer. You have to hook it up, start the engine, check idle timing and then run it up to 3500-4000 and check to see if its has advanced. Usually somewhere between 34-36 degrees advanced.
As a start, I would grab the distributor (with the engine off) and see if you can turn it by hand, if not, borrow an ignition module from somebody and try it first before you buy one.
09-11-2002, 12:12 PM
#9
Charter Member #737
Charter Member
Originally posted by KC Baja
What would cause it to not advance? Would it be the module on the exhaust riser or the smaller module in the distributor? I could replace either one myself but I'd rather not spend the $$ if it's not necessary. I've never checked timing myself and not sure where to start, besides buying a timing light. I know there's alot of OSO'ers here in KC. If anyone local could lend me a hand, I'd supply the adult beverages.
What would cause it to not advance? Would it be the module on the exhaust riser or the smaller module in the distributor? I could replace either one myself but I'd rather not spend the $$ if it's not necessary. I've never checked timing myself and not sure where to start, besides buying a timing light. I know there's alot of OSO'ers here in KC. If anyone local could lend me a hand, I'd supply the adult beverages.
