The season is upon us, and so is my headache

Gents and Ladies:<br /><br />Been a while since I've posted... but seeing as the season is nearly here for us Manitoban/Canadians, I'm starting to feel the itch again of being out on the water... of course along with this comes the un-remedied headache of last season.<br /><br />Now I've done a fair bit of searching, and have for the most part come to the conclusion that I may have 2 problems... 1) A bad power pack, and; 2) A bad rectifier.<br /><br />Engine:<br />1990 Evinrude 70HP, rebuilt two seasons ago. Approximately 70Hrs on it. VRO disconnected and pre-mixing.<br /><br />Problem Symptoms:<br />Engine runs fine for 5-10 minutes. Once warmed up, and from approximately 3/4-WOT, engine begins to buck... almost like completely loosing ALL power for split seconds. Like the fuel or spark is being cut off for split seconds and then kicking back on again. This is not a condition where the engine cuts back to a specific RPM... but feels like a complete loss of power. Further to this, add the fact that if I back off the power to 3/4 or less, while keeping the boat on plane... no problems. In addition, before this loss of power is experienced, my tach drops back to 0... when I back off the throttle, the arm on the tach begins to come back up as the throttle is reduced.<br /><br />The other thing too is, the battery still seems to have plenty of power for tilt and starting... So if the rectifier was bad one would think the battery would eventually simply die and not have the power to operate the tilt pump and/or start the engine...<br /><br /><br />Things I've done to attempt to remedy:<br />1) Replaced fuel lines<br />2) Tried pumping bulb when it happens, with no change in condition<br />3) Running on Muffs, used hair dryer on individual coils to eliminate/prove a heat/electrical expansion problem with the coils, with no luck and/or clues<br />4) Replaced water pump, which incidentally caused the engine to run MUCH MUCH cooler, and with higher water pressure, but did not cause any change in symptoms<br /><br /><br />I have not:<br />1) Checked resistance of electrical components<br />2) Replaced any electrical components (due to the $$$ involved in doing so without knowing what the problem component is)<br /><br /><br />So, given the fact that while the season is upon us, but not quite here yet... I cannot run the engine yet. Looking for suggestions as to what to do next and/or what it is based on my description above.<br /><br />Thanks SO MUCH in advance.<br /><br />Ben

Re: The season is upon us, and so is my headache

To test the rectifier ,with ohm's set to high, hook your + test lead, to the yellow rectifier lead, the other to ground. Note your reading, and reverse leads. One should read zero, the other infinity. Do the same on the yell/grey lead . If you dont get these readings, your rectifier is bad. <br /> Im not saying it is or isnt your problem , just thought you could rule it out.<br /> KYHunter

Re: The season is upon us, and so is my headache

Ben,<br />I had a similar problem. Check the carb. Especially the float bowl. Thats where I found my problem.<br /> Next thing I found helps out is when you fuel up, take a rag and wipe the spout. If you fill up at a marina, not usualy dirty. But, at land based fuel stops, you would not believe the crud that shows up.

Re: The season is upon us, and so is my headache

Did you try the heat gun method on the powerpack or just the coils?Also insure that the safety lanyard switch on the controls is not intermittedly grounding the ignition.If your safety lanyard has the rubber cap type switch depresser ,they are prone to stretching out over time.I'm pretty sure your controls have the fork type safety lanyard switch positioner though.Check to be sure.

Re: The season is upon us, and so is my headache

Hi all.. thanks for the responses. Have not had a chance to check the ohms on the rectifier yet... but wanted to reply to a couple of things.<br /><br />I tried the heat gun method on the powerpack and the coils. As for the lanyard, you are correct, it is the fork style switch.<br /><br />Maddog: With regards to the carb problem... Why would it be that after 5-10 minutes the problem appears? Would it possibly be because the float might not be properly metering the fuel and therefore draining too much from the bowl... thus not supplying enough fuel? Also, if this were the case... why would my tach be acting up?<br /><br />The tach was the main thing pointing me in the direction of an electrical/ignition problem... is it possible it could be the stator?<br /><br />Thanks again<br /><br />Ben

Re: The season is upon us, and so is my headache

check the ignition switch and nutral safety switch.<br /><br />good luck

Re: The season is upon us, and so is my headache

A couple things to check out if you haven't:<br /><br />

So if the rectifier was bad one would think the battery would eventually simply die and not have the power to operate the tilt pump and/or start the engine...<br />

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Easy enough to check- Check voltage at the battery not running and then when running. Should be a voltage rise if the rectifier is good.<br /><br />Fuel problem- Try a different fuel tank, connectors, Bulb, Etc. That would eliminate fuel supply.<br /><br />When this happens on the water, stop right away and pull the plugs. Check their condition(Wet, Dry)??<br /><br />Check for spark on all 3 at that time, also.<br /><br />Check the spark advance to make sure it's advancing all the way at full throttle.<br /><br />Check for linkage that might be pinching wiring at high throttle.<br /><br />Just a few things to narrow it down...

Re: The season is upon us, and so is my headache

New information!!! Have found the following:<br /><br />Now when tach cuts out, seems the engine runs fine!!??? Before tach cuts out, rectifier is overly hot... enough so that you can barely touch it.<br /><br />Found that when pressing on the fuel line inside the cowlings and by the in-line filter, a pressure release can be heard once in a while. Think this may be unrelated...<br /><br /><br />Thoughts??

Re: The season is upon us, and so is my headache

What brand tach is it? <br /><br />Just for giggles, disconnect the tach entirely and see what happens.......

Re: The season is upon us, and so is my headache

Its a Lund tach using the standard OMC harness. Marine shop said it would work fine for my application.<br /><br />Plan on heading out on the river with the wife tonight for a cruise. Will try disconnecting it and see what happens. Seems to me that if I recall correctly, the problems started when I installed the Tach??? What reason would there be for this... I'm curious

Re: The season is upon us, and so is my headache

Hmmm... someone tell me if I'm crazy but I think I just had a revelation.<br /><br />Hypothetical situation:<br />Weak battery, causing charging system to work overtime. Rectifier begins to overheat due to additional draw while attempting to charge the battery. While this is happening, also causing stator to warm up and stop working properly and/or not provide enough volts to power pack, causing high speed miss. Rectifier finally overheats and cuts out (when tach cuts out). Attempts to charge the battery are no longer, allowing stator to provide full-time charge to ignition circuitry explaining why it would work fine once rectifier cuts out??<br /><br />Does that make sense or am I way off the map?

Re: The season is upon us, and so is my headache

I've worked on 2 motors with the same symptom as yours except for the problems with the tach. One motor had a bad stator and the other motor had some corrosion on the taper shaft between the flywheel and the crank. If you have a puller, pull the flywheel and clean the crankshaft taper and the hole in the flywheel with some emery cloth.

Re: The season is upon us, and so is my headache

i agree with realdutch, check ignition switch and wiring, kill switch and wiring, souds like intermitent short. is this happening on rough water as well as calm.

Re: The season is upon us, and so is my headache

OK. So, I think I may be chasing two ghosts my machine!!<br /><br />I'm beginning to think that the tach problem is unrelated to the mid-to-high speed miss.<br /><br />Last night was out on the river here in the 'peg (as we call it). Began to act up almost immediately (before I went out went through just about every connection I could find and cleaned all terminals with some emery cloth). Following that, disconnected the rectifier just to rule it out as a suspect... still acting up. Disconnected the tach entirely, still acting up. Funny thing is, decided to go for a cruise any ways... began running fine again after running for I'd say 15 minutes at 4-4500RPM.<br /><br />As near as I can figure, the sequence of events is as follows:<br />1) Boat warms up in the first few minutes and begins acting up (starts with slight and bucking and missing, sometimes to the point where I'll lose plane completely and the motor all but dies)<br />2) Eventually, after 10-15 minutes, the tach drops off to zero... and bucking **Begins** to stop.<br />3) After a couple of minutes of the tach being zero'ed and bucking **beginning** to stop... Engine begins to run perfectly fine with the exception of the tach not working....<br />4) After engine has cooled for 15-1/2hour, return to step 1... <br /><br />I'm AT AN UTTER LOSS...<br /><br />The above is completely reproduceable! Happens every time with absolute predictability!!! Although the "acting up" seems to be worsening every time and am afraid soon it will simply die! This has left me even more confused about where to look than when I started!<br /><br />I don't even know what to think any more... grabbing at air at this point. Could it be that my choke is stuck open somehow? Is the engine flooding itself when it's been sitting? If so, how would that explain the fact that for the first minute or two it runs fine at high speeds, and ALWAYS runs fine at low RPMS. Is it possible that the fuel pump isn't working quite up to snuff and not completely filling the float bowls until it's been run for a certain period of time? That initially fuel is still left over from the last time out, and after the first couple of minutes drains, but finally comes around and starts pumping fuel properly?<br /><br /><br />I know it's virtually impossible to diagnose a problem over the "interweb" , but I'm hoping eventually I'll nail this problem with all of your help!!!

Re: The season is upon us, and so is my headache

Also, to answer tashasdaddy, it does happen on rough as well as calm water! No ryhme or reason...<br /><br />Walker: Can you explain to me a little more why corrosion on the taper shaft would cause this type of symptom?<br /><br />Thanks in advance.<br />Ben

Re: The season is upon us, and so is my headache

Do not unhook the rectifier and run the motor. Unhook the tach and run the motor. Unplug or remove all wires from the tach.

Re: The season is upon us, and so is my headache

I unplugged the tach at the console (Three wire harness). Or are you suggesting unhooking it from in behind the tach itself?

Re: The season is upon us, and so is my headache

Just to answer a few questions:<br /><br />

Could it be that my choke is stuck open somehow?

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Nope. You have a primer system. If it was open and allowing fuel through, it would not run due to an overly rich mixture.<br /><br />

Is the engine flooding itself when it's been sitting?

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Doubt it because of #1. You could pull the plugs and check them out.<br /><br />

Is it possible that the fuel pump isn't working quite up to snuff and not completely filling the float bowls until it's been run for a certain period of time?

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One way to find out is to pump the primer bulb when this happens. By doing that, you are essentially becoming the fuel pump and filling the carb bowls with fuel.<br /><br />Also, did you check these out?<br /><br />Check the spark advance(Timer Base) to make sure it's advancing all the way smoothly from idle up to full throttle.<br /><br />Check for linkage that might be pinching wiring at high throttle.<br /><br /><br />BTW-I have the same motor as you and am curious as to the outcome, just in case....

Re: The season is upon us, and so is my headache

Rick:<br /><br />Have had a passenger try pumping the bulb when it's happening to no avail. Also tried burping the choke when it's happening... no change. However, keep in mind my VRO feed to the pump is plugged with a bolt and I pre-mix 50:1.<br /><br />As per your previous post, I did a thorough check of wiring last night before heading out and didn't find anything that would be getting pinched by the throttle/shift linkage (even pulled all connectors apart, cleaned and re-tightened my ground, looked for burnt wires). <br /><br />Now it's been a while since I've dealt with my timing (Since I rebuilt it 2 seasons ago), but when advancing the throttle last night, the timmer base looks like it's at full advance at about 1/3-1/2 throttle. With regards to timing, I'm curious what you're thinking? If it was a timing problem, would the problem not persist? Rather than going away after a time?<br /><br />

Re: The season is upon us, and so is my headache

Another thought. Did my model come with the S.L.O.W feature? Is it possible it's freaking out? If it is possible... is there a way to disconnect it to test?