View Full Version : ignition problems
I have a 96 PS190 350 tbi, and need some help! I let my buddy drive the boat for awhile, then I noticed he was doing around 4000 rpms and had done so for the past 8-10 miles. About the same time I realized he was turning such high rpms, the boat started losing power. We made it back to the dock, but felt like it was running on less then 8 cylinders. Upon further inspection, I noticed 4,5 and 6 had sparatic spark. I changed the cap and rotor button, put new plugs in, checked all the wires, made sure the distibutor had not moved and still got the same result. I took the ignition control module to Autozone and it tested bad. I purchased a new one from them thinking this would fix the problem, but when I installed it, nothing changed. My next step is to check the timing and make sure it didn't skip a tooth on the timing chain. Anyone have any suggestions ??
How many hours are on the motor? I doubt that the timing chain skipped a tooth- they aren't plastic and the motor probably hasn't seen the kind of use that would cause it. The rotor button was changed" you mean the one in the cap, right? Why would you not change the rotor?
When was your raw water impeller changed last? When was your oil cooler cleaned out? What is the other service history for the boat/motor?
If you sesarch here for other similar threads, you'll see quite a few with similar symptoms and you'll also see that I, and others have said that fuel issues cause most driveability problems. Check your fuel pressure, take a fuel sample, check the spray pattern from the injectors, clean the flame arrestor, make sure the fuel shutoff isn't closed on the tank and change the fuel filter. If these all check out or don't make any difference, change the plug wires if they're more than 3 years old. Then, do a compression and/or leakdown test.
What did the spark plugs look like when you removed them? Did any look like they had been steam cleaned? Were they wet with gas or water? Did they look burned?
Squeeze the exhaust hoses and notice if one or both is particu;arly soft. Look at the exhaust flaps for melting if the hoses are soft. If they're melted and the hoses are really soft, you overheated it and these should be replaced. Also, look on top of the motor for melted wires and wire loom. If the temperature sensor wire(s) (yellow and black, not the tan wire) are melted together or are grounding to the motor, the ECM will think the motor is overheated, even cold. There are two sensors for temperature- one for the gauge (the one wire sensor with a tan/black wire and the two wire ECM sensor with yellow and black wires.
JimN, Thanks for the response. I should have given you more info. The boat has 1200 hours, but we rebuilt the motor at 1000 hrs and has ran great all summer. The plugs in the three cylinders, (4,5,6) were wet, the other cylinders were running rich having a black dry look instead of a tan color. I do not believe this is a fuel problem nor did the motor overheat (according to the gauge). I service the boat myself and put a new impeller and housing in at the beginning of summer and the oil cooler was cleaned at the same time. It has new wires and plugs. The distributor cap and rotor button were replaced, I am not sure what you are speaking of by changing the rotor. I will check the temp wires at the ECM and make sure the are not melted together. Does the engine shut down cylinders if it thinks it's overheating? I know the three cylinders are getting intermittent spark and the ignition control module was bad (but the new one didn't fix the problem), I may try a new pickup coil, they are inexpensive. Again thanks for the response and let me know if you can think of anything else to check.
11-28-2005, 08:55 AM
Check the wire harness that goes from your distributer to you resistor i am not sure what the specs are but each wire has certian volts or amps it should be if these are not right you will not get proper spark wich will cause you to misfire.
P.S. don't let friends borrow the boat they will never realize how much TLC we put into these things and will just rag them out.
Motors without points don't usually have a resistor and HEI motors definitely don't have one.
JB3- who did the rebuild and when the heads/intake manifold were reinstalled, was gasket sealant used on the mating surfaces? Also, when the plugs were checked, were they wet with water or gas? It makes a difference. You need to do a compression test NOW. This time, do it cold, without running the motor. If it checks good (150 pounds is a good number to have as an average), remove the lanyard and the distributor plug with the purple/white wire in it, pull the plugs and crank it over for 5-10 seconds. Put the plugs back in, reattach the distributor harness and lanyard, then run it till it's at normal operating temperature. If it runs lumpy immediately, check for spark at the plugs that aren't firing by inserting a known good plug and grounding the body of the plug. DO NOT hold the plug or plug wire in your hand when you do this. This ignition system puts out over 50,000 volts and you don't want to get zapped by this. Speaking of plugs and wires, what are you using for these? Your motor needs AC MR43T. They are available, regardless of what some auto parts stores say, and work better than most others. If you tried to reuse old wires, don't. Old wires are prone to crossfire and if this happens, the spark can not only jump to other wires, it can jump to ground and you won't have spark to the plugs.
What are you referring to when you say rotor button? The rotor is mounted on the distributor rotor shaft and can be hard to remove, but when it's old, it needs to go. Put some grease on the shaft when you replace the old one. There are also some rare cases of a hole burning through the rotor, going down from the cap to the rotor shaft. This causes a hard misfire at high RPM, under load.
FYI, the oil cooler should be checked every time you take the boat out, not just at the beginning of the season. This is stated in the owner's manual, too. Your gauge wouldn't necessarily show an overheat if the oil cooler was clogged. The sensor needs to be immersed in water or coolant in order to show the temperature accurately. Being near the water won't show you anything you need to know. When I said to check the wires, I didn't mean at the ECM, I meant along the way from the sensors all the way to where they lose contact with the intake manifold or block. In an overheat, the block gets very hot and anything in contact that can melt, will. The only way to know if it overheated or not is to check the ECM diagnostics for codes and overheats. The gauge is as useful as a warning light when there's no water getting into the motor.
The ECM doesn't kill spark to any cylinder(s) in the event of an overheat. It does, however, go into RPM reduction mode by alternating the injectors on TBI or alternating injector banks on MFI motors. RPM reduction mode means SHUT IT DOWN, not limp home.
If you idled for any length of time before checking the plugs, don't worry about whether they were straw colored, just check for fouling or water wetness.
You still need to check your fuel pressure and if you don't remember when the fuel filter was changed last, do it now. There is also a fuel pickup tube in the tank and occasionally, this gets clogged with whatever may have gotten into the tank.
If the tank has run dry in the past, especially if this has happened more than once, your fuel pressure will read low. Impellers burn up when this happens and you won't develop adequate pressure in high RPM situations, which causes the motor to run lean. Lean at high RPM burns pistons, valves, etc.
Why, exactly, did the motor need to be rebuilt at only 1000 hours?
11-28-2005, 12:51 PM
FWIW, I've heard many a story about replacing a bad part with another defective one from the parts store. Maybe check the new ign control module or try a third one.
11-28-2005, 03:51 PM
I know you think it's electrical. But, something tells me to check your fuel pressure like JimN suggested. To me, it sounds like a clogged fuel-pump. There is a screen on the inlet side of your pump. Mine got clogged a couple times from shavings in my new gas cans.
11-28-2005, 04:44 PM
JimN my boat had points at one time, but the guy i bought it from changed it over to electronic ignition. i still have a resitor do i need to take out the resitor and patch the wires straight though? my boat has some trouble firing up. its wierd because it usaully starts the best, the first time its fired up for the day. i also think i need plug wires because when i lift the engine hatch up at night i can see the spark going through the plug wires it kind of glows.
sorry to thread jack
If you see sparks from/on/between the plug wires, you definitely need new ones. That can be the issue when the motor has warmed up, too.
11-28-2005, 06:30 PM
figure out who made the conversion, and see if the resister should be removed/bypassed.
11-28-2005, 06:50 PM
thanks for the info guys, and sorry about the thread jack.
03-17-2006, 08:20 AM
My engine has 2100 hours on it. Somebody told me that I should change my timing chain... What do you think? Is it an hard work to do?
Do we need some special tools?
I have a 351 FORD (Indmar) year 93. Where is it located? Under the circulatuion pump?
thanks in advance for your help.
Put a timing light on it and see if the timing mark jumps around (not just at idle- it'll obviously move with increase/decrease in RPM, but at a particular RPM, it should be stable). If it does, it may be loose. If it doesn't jump, it's fine. Another thing that can make the timing mark jumpy is the distributor shaft bushing. You might want to re-check the gap for the pickup coil on the distributor, as well as the advance springs and weights. They're under the plate on the distributor. Also, make sure the distributor is grounded well. It grounds to the block through its base and over time, this can get dirty or rusty and cause problems with spark.