Troubleshooting Intermittent Problem

[andyusmc]

Howdy all,
Just joined, looking for some confirmation before I start spending money...
I bought a used Tracker with a 1987 Classic 50 Merc outboard last year. The engine seems to have low power. With just me, I will gradually get up on plane and run about 5000 rpm. If I fill the live well, sometimes no plane. More than one person, no plane. Engine stays at about 3k rpm.
Some trips worse than others. I found a slightly corroded coil, replaced, ran good for a while (maybe wishful thinking on my part).
I have done the following: rebuilt the carbs (I have an odd carb with no integral fuel pump). I disconnected the oil injection and I mix the oil (not in response to this problem).
I decarboned the engine last year with Seafoam.
I believe the problem is ignition.
I measured the stator resistance as follows:
red to red/white = 151 Ohms (high depending on manual/part installed)
blue to blue/white = 6670 Ohms
DVA red to red/white (cranking) = 48 V
DVA blue to blue/white (cranking) = 309 V
DVA red to red/white (running - idle) = 140-170 V
DVA blue to blue/white (running - idle) = 310 V
Trigger DVA to ground all 4+ V
Purple to white = 11-12 DVA running
Brown to black = 11-12 DVA running
In the manual I have, under "Engine will not accelerate beyond 3000-4000 rpm" section, it states "Connect a DVA meter to the red wire and red/white wire and do a running test. The DVA voltage should show a smooth climb in voltage and remain high through the RPM range. A reading lower than the reading on the blue wires indicates a bad stator." I am assuming the "blue wires" are the blue and blue/white stator wires.
The boat is on the trailer, and I am running on the hose, so I can't rev too high, but, the DVA voltage never exceeds the blue stator wire voltage.
I am tempted to replace the stator. And if I have the flywheel off, I may as well replace the trigger.
Any thoughts? Do I need to put the boat in the water and run under load to troubleshoot properly?
Thanks
Andy

 

[cannonford57]

Re: Troubleshooting Intermittent Problem

andy you have been very through with your diagnostics...since you have acess to a dva meter i guess you have a inductive timing light...on the water,(not a hose)get someone you trust,buy them lunch,take them on a boat ride....clip the light on each of the plug wires respectively ,have your bud accelerate to planing speed...(if you trust him, if not he would be the on on the back of the boat i guess)if around 1800 to 2000 rpm the light goes out you have a stator problem......if 2 cyls go out you have a trigger problem....cheaper than buying ign parts huh...and if your name is any indication of your status let me be the first to welcome you to the forum and thank you for your service to our country.

 

[andyusmc]

Re: Troubleshooting Intermittent Problem

Thanks for the response. Wow, these threads get buried quick. I think I will have to go to the lake (sucks here in SoCal, you have to pay and they are only open certain days). Hope I can get it running right.
I am actually retired now from the USMCR. 25 years was enough. I still miss it though.

 

[andyusmc]

Re: Troubleshooting Intermittent Problem

Well, now I am stumped. I took a friend for a ride today. On the trailer, in gear, WOT I get about 3000 rpm. All of the cylinders are firing, timing is advancing. Ignition system checked out good as far as I can tell. We launched and tooled around the lake for a bit. If my buddy got in the front of the boat, we could get kind of up on plane, and the boat would accelerate a bit. The engine went up to 4100 rpm or so. This makes me think it is a fuel issue, not ignition. I came home, pulled the carbs, and the only think I can find that makes me pause is the float level. With the carbs upside down, I can set them in accordance with the manual (Seloc). With the carbs right side up, the plastic float does not have an adjustment. The manual says it needs to be 1/32 to 1/64 above the main jet. Does that mean the main jet orifice (hole), or the main jet hex nut? Either way, it looks like the float descends too far. I can't bend the plastic stop to adjust it. I can bend the sheet metal tab to set the float level with it upside down.
I guess my question is this - what would the symptoms be if the float descends too low? Could I starve the engine for fuel?
Thanks for any input.

 

[andyusmc]

Re: Troubleshooting Intermittent Problem

Additional information. Bought a new fuel tank and new fuel line today. I cleaned the carbs last night. First trial was on the trailer, same fuel line and tank I have been running. In gear, WOT = 3000 rpm. Launched the boat, same deal. Best we could do was ~4100 rpm. With me alone, about 4250 rpm. Changed fuel lines from the engine back, no difference. So if it is a fuel problem, it is confined to the engine area. Since I had all that off yesterday, I am inclined to believe it is not there either. So I am back to ignition again. I can't help but think that the high speed coil is the source. I guess depending on which book you have, the resistance is high. Not sure what the output DVA should be, but it is less than the blue coil.
I think I will probably replace the stator.

 

[JKP]

Re: Troubleshooting Intermittent Problem

Andy
Same story here....different engine though...I have a 96' 90 HP....stator readings seem to be close enough to spec, ......but on the water under load, the engine just will not develop the RPMs to get er up on plane. I have come to the conclusion with my "boat guy" adviser, that it needs a new stator....side note...my engine had a Merc tech bulletin come out about 10 years ago advising replacement to new upgraded stator, but my engine had still had the original.

 

[JKP]

Re: Troubleshooting Intermittent Problem

By the way
Semper Fi Marine !
JKP
HMLA 773 Atlanta

 

[andyusmc]

Re: Troubleshooting Intermittent Problem

Same at you, Devil Dog. CWO4 USMCR, retired from HMLA-775 after a couple trips to the sandbox in 04 and 05.
I will post what I find, it seems there is a lot of "lost power, please help" posts here that don't get answered.

 

[JKP]

Re: Troubleshooting Intermittent Problem

Hey I was with you guys in 05 in good ole TQ....I was one of the 773 augment pilots to go over there with you on your second TQ adventure. In fact just saw a bunch of you 775 guys out in SoCal this past week as the New Orleans Det, and the Johnstown Det of former Coyotes have been at Campen supporting EMojaveViper.
Always good to run into an old friend in the small world of the Corps.

John Pitchford
LtCol USMCR

 

[CharlieB]

Re: Troubleshooting Intermittent Problem

Take your DVA Meter out on the water and check the running output anywhere over 2500 RPM.

Low speed output is generally falling off by 2500 RPM, High speed output must be surpassing low speed or ignition voltage will not rise sufficiently to bridge the increasing cyl pressure of higher RPM's.

Also try squeezing the fuel bulb to raise fuel pressure, which would indicate a weakened fuel supply

Any, momentarily 'bump' the choke/enrichener', which would indicate a carb fuel restriction.

I doubt if you have a fuel problem, as you have very well tested and shown a weak high speed winding in the stator. Since there is NO RETURN, you may want to be absolutely certain by performing another running test.

 

[andyusmc]

Re: Troubleshooting Intermittent Problem

I have squeezed the bulb many times. It always stays firm. The carbs appear set up properly. I am still waiting for the stator to get here. I think that should do the trick. Hope so, anyway.

 

[andyusmc]

Re: Troubleshooting Intermittent Problem

Well, the poor performance continues. I ordered and received a stator and trigger. The trigger did not have the proper bushing to attach it to the advance rod linkage, and since I was only replacing it because I had the flywheel off anyway, I decided to install only the stator. Ran the boat today, same problem. Will not get on plane, only runs about 3000 rpm. I really didn't expect this.
As a refresher, I have checked compression (all four about 130), checked the fuel system (new tank and hose), cleaned carbs and replaced gaskets. I ran all of the ignition system checks I can find, and the only indication was the stator high speed windings. So now I have changed that. I will change the trigger when I get the proper bushing, but I have my doubts.
The fuel line bulb stays hard, squeezing while underway has no effect. The fuel pump spurts fuel when the motor is cranked, but I have not measured how much.
I tried spraying some starter fluid into the carb while underway today, and the motor slowed down some. This makes me think that it has to be timing or ignition.
I suppose if the trigger does not improve things, then the switchbox will need to be changed. Starting to get really frustrated with this thing!

 

[CharlieB]

Re: Troubleshooting Intermittent Problem

Reviewed your postings again but didn't find any mention of prop size.

Ex-marine?

How much bigger are you than the prior owner?

If a smaller person propped the motor for highest speed, and you outweigh him by 50 lbs, plus full live wells, that 50hp may not be enough motor to spin up the same prop.

Are you anywhere near a prop shop, spend a few minutes on the phone with a pro and see what pitch is recommended for that boat/motor combination with the loads you carry in it, compare that info with your current prop pitch. Some prop shops will work with you and let you try another prop before purchase to really feel the difference.

Many of us have 2,3 or more props and select which prop to use depending upon how we are loading our boat that day, trip, or weekend, more or less persons (weight), speed vs holeshot, towing tubes, etc., varying pitch up or down within a range of a few inches. A couple of inches difference in pitch can make ALL the difference.

 

[andyusmc]

Re: Troubleshooting Intermittent Problem

I guess I forgot to mention that. I did put a new prop on, there were some minor dings on the old one. I got the pitch from the manual - same as the original (13 pitch). I suppose I could weigh the boat - I used the 1000-1500 lb line. Perhaps the boat is substantially heavier - it is a 1987 TX-17. I wonder if I would be better off with a 12 pitch, or even an 11. Would that make 2000-2500 rpm difference? The motor just doesn't seem to have any guts at all. I still have a new trigger to put on, so I will try that next. I don't expect it to help, but the ignition manual says that is sometimes the cause.
I am about 200 lbs, my kids are about 50 and 70. I have a neighbor who is about 260 who goes along occasionally. Even on the trailer, the boat will not rev over 3000 rpm.
Should I get full rpm with no movement of the boat (but in gear)?
Thanks for the response.

 

[CharlieB]

Re: Troubleshooting Intermittent Problem

Standard rule of thumb, one inch pitch changes WOT RPM @ 200, not 2000. But if you now have a 4 blade instead of an original 3, then all bets are off.

Compression fine
Fuel pressure/flow fine
Carbs checked out/clean, fine

Mechanically solid
Fuel system checks

Al that is left is thoroughly checking the ignition system

WOT timing, checks
Spark intensity, must be bright hot blue crack 7/16 inch, check
High speed stator windings output at cranking, then should rise such that by 2000 RPM is greater than the low speed windings cranking.

Trigger wires possibly failing when moved to full advance position?
Test again with DVA Meter, disconnect throttle cable such you can fully advance timing while cranking to see if voltage falls off at any point in the travel

I have recently found a too tall flywheel key which would not allow the flywheel to fully set down, it 'wobbled' at speeds, slightly brushing against the stator on one side. When this happens the stator becomes part of the magnet and that portion of the magnet no longer contributes to electrical generation, voltage fell off. I almost replaced the stator, but it ohmed fine, and when I used a battery and light to load test it also passed fine. I kept looking until
I noticed the lack of contact pattern on the crankshaft/flywheel taper.

I suspect we are overlooking something that should be glaringly obvious.

Throw out all preconceived notions and start over at square one.

DO NOT ASSUME that because you have already done something or already checked everything, that they are all still fine, cause obviously something is not, we just have to prove it wrong so you can make it right again.

 

[andyusmc]

Re: Troubleshooting Intermittent Problem

Thanks for the reply. I am kind of a stubborn bastard, and I will keep after this until I figure it out. I put the trigger in tonight, hopefully will get a chance to op check tomorrow or Sunday.

 

[ENSIGN]

Re: Troubleshooting Intermittent Problem

Check the magnets under the flywheel,sometimes they move out of place.

 

[mastrofury]

Re: Troubleshooting Intermittent Problem

Just want to join the club. My merc. seems to be doing the same thing. although mine seems like a down cyclinder at WOT. Mine will sputter like 1 cylinder is comming and going. Once I get up on plane it seems to smooth out but still down on RPMs . I been threw the fuel system many times. Im thinking trigger myself.

 

[andyusmc]

Re: Troubleshooting Intermittent Problem

Well, the saga continues. Replaced the trigger last night, no help. With just me in the boat, it accelerates strongly to about 3000 rpm. Then anything after that is due to reduced load. Today by myself I (gradually) got up on plane, playing with the trim, and once there ran up to about 4500 rpm (downwind, wind speed about 15 mph). When I made a gradual turn up wind, without touching the throttle or trim, the motor speed dropped to about 4100 rpm. Any load at all on this motor just kills it.
On the trailer, in gear, still tops out at 3000 rpm.
One other thing I have noticed but not mentioned. Full forward on the throttle is not where the engine runs best. If I go forward to the stop, I can hear the engine kind of missing, and it slows down. If I back off just a little, the engine speeds up some, and the miss or whatever it is clears up. I am told the switch boxes on these engines are notorious for going out. I hate to go spend another 200 bucks or more. Troubleshooting by substitution is almost never the right thing to do.
I have not checked the new trigger and stator with the DVA meter yet, so I suppose that is next on the list.
Could the kill switch be somehow partially grounding out at speed? Seems unlikely, but I suppose I could disconnect it and go for a run easily enough.
Can a Merc dealer test the switch box?
Thanks for any help.
Andy

 

[edeere]

Re: Troubleshooting Intermittent Problem

Andy,
I just bought my first boat 3 weeks ago and am working on a low RPM issue as well. The elevation I am at vs. where the boat came from is 3000 ft higher. I had a 25 pitch 4 blade on and could only make 2200 RPM with my Merc 200 EFI. I visited the local prop god and he loaned me a progressive pitch prop that was also 25 pitch. My Rs came up to 3200 and I could at least plane out this trip. I have since raised the jack plate 1" higher per his instructions and waiting to get back in the water to test out. He suspects I may have to wind up with around a 21 pitch before we finish. I dont know if you transported your boat into a different elevation situation or not but if so it might be something to consider.