2000 250HP OX66 Charging Problem

[DennisG01]

I've done some searching and checking in a service manual (although I'm not 100% positive that the manual is for my year engine). I'm "OK" when it comes to electrical stuff with Mercruiser's, but less so with this outboard as I have little experience (none) with big OB's.

So... I noticed the Yamaha dash voltage gauge blinking at 11.8 (same for both batteries). I tested the voltage with a good voltmeter right at each battery. With the engine off, I get about 12.3v (no idea of age of batteries). With the engine running I get 12.0v. The engine starts right up and runs, although at this point I've only ran it (1) for about 30 minutes during the test ride before purchasing and (2) about a total of 30 minutes on a hose (it doesn't seem to like to run as smooth on a hose).

First, I started poking around (trying to find the voltage rectifier, which I have not, yet). I was going to try and check voltage there - but I was/am still a little unsure of how to do that as the manual says to remove fuses? Anyways, I found this wire broken off. It's the green one with the small clamp on it at 10:00. It should be connected to the silver post with the green dot on it. I'll reconnect this tomorrow and check things out, but what is that?

Second, the other clamp at approximately 3:00... it looks like those leads might be the charging leads that go to the batteries?

Third, should the charging voltage be roughly what it would be coming from an alternator in a boat or a car? Meaning, roughly 14v?

 

[seasick]

Re: 2001 250HP OX66 Charging Problem

The three green wires on the upper connector are the connection from the Lightning Coil ( alternator in effect) to the rectifier. The output of the rectifier passes throughan 80 amp fuse and then on to the battery (or battery switch)
At medium revs, the charging voltage will run about 14.2 volts or so.
The service manual has a section on testing the lightning coil and the regulator.
The output from the fuse should be red/white and or red.

Check your fuses first. I don't know what the disconnected green wire is. If it looks like it was connected to that post you mentioned, I maight try reconnecting it but I would feel a lot better if someone had a photo of their connections.

 

[DennisG01]

Re: 2001 250HP OX66 Charging Problem

Yes - I'm positive the green wire was supposed to be connected there (and it appears to be the one in the diagram just below the connector you referred to). The ring terminal is broken - part of it remains on the post, part of it remains on the wire. I believe it was just barely hanging on/connected and when I started moving wires around looking for breaks, etc, it popped right off.

I did see the section in the manual about checking the lighting coil and rectifier - but it was a little confusing. I guess once I physically find the rectifier, it will make more sense. I'll check the fuses, too.

I thought I heard this somewhere... Is it normal for an outboard to run rough on a hose? I've only run small outboards out of the water before and it was easy enough to get them in a garbage can. For what it's worth, it ran flawlessly during the test drive.

 

[lime4x4]

Re: 2001 250HP OX66 Charging Problem

On my 87 150's i have around 12.5 volts at an idle then when i get up around 1500 rpm's i start to show 13.6 volts. Mine also idle a little rough when connected with a garden hose

 

[seasick]

Re: 2001 250HP OX66 Charging Problem

I assume that you are referring to running on a hose using muffs and not the flush port.
You would think that running on a hose shouldn't affect engine performance but in reality there are several things that could affect how the motor runs when on 'municipal' water. The various parts of the motor my cool or heat up differently due to the possibility of lower water flow. Some sections may locally overheat or some may never heat up enough.If the motor not under load, it may never get to real operating temps.
More importantly, having the lower unit open to the atmosphere as when on land, changes the exhaust back pressure and that can affect engine performance. The motor is designed to blow exhaust through the water. Removing that back pressure changes the flow characteristics of the exhaust in effect 'de-tuning' it.

 

[gw204]

Re: 2001 250HP OX66 Charging Problem

I'm pretty sure the green wire you are referring to is for the trim/tilt system. Now that it's completely broken off, do you have trim up and down functionality?

For your voltage problem, the first things I would check are your battery and battery switch connections. Are they clean, tight and corrosion free?

 

[DennisG01]

Re: 2001 250HP OX66 Charging Problem

Yup - you're right - trim/tilt. It must of been making just enough of a connection until I gently pulled on the wire and the ring terminal broke. It appears the wire was just a bit too short, thereby placing some stress on the connector. I added a length of wire and a new terminal and that part is good to go.

For the charging problem... Yes, agree about battery connections. That is the first thing I did - I disconnected every single one, cleaned (brass brush), tightened them back on and then sprayed with some terminal protector. I also looked for loose/corroded connections at the engine side, but that was all very nice.

Now that I know where the rectifier is, I checked for voltage at the downstream side of the 80a fuse block (where the wires from the rectifier enter the big fuses). I only got 12.0v there with the engine running, same as on the batteries. So at this point, I've at least eliminated everything on the upstream side of the rectifier. BUT... what do those two notes in the service manual mean? Did I check for voltage incorrectly (I didn't remove anything).

I was going to disconnect the connection that Seasick mentioned (the three-wire connector coming from the stator) and check for voltage there, but I wanted to double check that that is OK to do with the engine running. Also, I wasn't sure what I should be seeing for readings there? I read a couple places online that it's AC voltage coming from the stator?


That makes sense about the running on a hose - I have plenty of water flow/pressure (I've tested it), but the back pressure makes sense. And, yes - I was referring to using "muffs" - I'm aware that it isn't recommended to run on the quick-flush hose... that it's only meant for flushing the engine with it OFF.

 

[DennisG01]

Re: 2001 250HP OX66 Charging Problem

Forgot to mention - I checked for voltage on BOTH sides of the fuse block and got the same 12.0v. I had also removed, checked, cleaned each fuse. Although they were quite shiny to start with, I still used a brass brush on them and used a little dielectric grease before reinserting.

Can anyone confirm if the voltage spec for the stator (in the service manual page above) is correct? In doing some searching, I keep coming up with a much higher reading, which contradicts the manual? Also, how do you check the voltage of the stator (at the connector Seasick mentioned) with the engine running? Is it OK to disconnect it or will that cause a backfeed of voltage into itself? The connector is sealed where the wires input.

 

[DennisG01]

Re: 2001 250HP OX66 Charging Problem

Did some more searching and found it's OK to disconnect the (3) green wire plug. I don't have a peak meter, but as it turns out I don't think it was needed (unfortunately). I was seeing (AC V) about 3v, 3v and 1.5v. I'll ohm test them to each other and ground, but next step, I think, is to remove flywheel and check out the stator. Worst case is to replace it... Maybe I'll get lucky and just have a broken wire somewhere... Never looked at one before so I'm just guessing here.

FYI, voltage spec for stator is "minimum" - I missed that part. I called a local dealer who also mentioned that "typical" V is more like 40v.

 

[seasick]

Re: 2001 250HP OX66 Charging Problem

Did some more searching and found it's OK to disconnect the (3) green wire plug. I don't have a peak meter, but as it turns out I don't think it was needed (unfortunately). I was seeing (AC V) about 3v, 3v and 1.5v. I'll ohm test them to each other and ground, but next step, I think, is to remove flywheel and check out the stator. Worst case is to replace it... Maybe I'll get lucky and just have a broken wire somewhere... Never looked at one before so I'm just guessing here.

FYI, voltage spec for stator is "minimum" - I missed that part. I called a local dealer who also mentioned that "typical" V is more like 40v.

I haven't debugged at that level so I am learning from your work. From what I see in the diagrams, you should not see conductivity from ground to any of the three coil leads.
When you measured the 3 volts was the motor running?
The fact that one leg read lower seems to indicate a problem.
Keep us informed. I am sorry you have problems but your information is very educational.

 

[DennisG01]

Re: 2001 250HP OX66 Charging Problem

No worries - any help is good help! I'm learning as I go.

Yes, volt tested with engine running and connector pulled apart. I should be getting AT LEAST 14v - so anything below that is no good - probably doesn't matter much whether they were all in compliance with each other?

Yes, according to my conversation with the mechanic, shorting each green wire to ground should be no continuity. I just tested that and it was, indeed, "OL" (over the limit, or no continuity or infinity... whatever one wants to call it). I then also tested each green wire to each other - he didn't have a book in front of him, but mentioned that there should only be a few ohms, at the most, each way... I again measured infinity. Although I may have missed it, I didn't find anything in the book to confirm this.

 

[seasick]

Re: 2001 250HP OX66 Charging Problem

No worries - any help is good help! I'm learning as I go.

Yes, volt tested with engine running and connector pulled apart. I should be getting AT LEAST 14v - so anything below that is no good - probably doesn't matter much whether they were all in compliance with each other?

Yes, according to my conversation with the mechanic, shorting each green wire to ground should be no continuity. I just tested that and it was, indeed, "OL" (over the limit, or no continuity or infinity... whatever one wants to call it). I then also tested each green wire to each other - he didn't have a book in front of him, but mentioned that there should only be a few ohms, at the most, each way... I again measured infinity. Although I may have missed it, I didn't find anything in the book to confirm this.

I would have expected low resistance between legs also. So it is looking like the stator may be the culprit. The pictures of the stator seem to indicate that it is a one piece assembly without obvious connections that could come loose. When you get to it, it may be obvious that is is bad. Hopefully no magnets came loose and physically damaged it but if they did, that too will be obvious.

 

[DennisG01]

Just a follow up here...

Not sure if I had mentioned this, but when my brother and I bought the boat the owner had a spare engine (he said one cylinder was bad) that he gave us, which we picked up from him a few days ago. So last night I checked the stator (the two resistance checks) of the spare engine and it seemed good. I pulled the two flywheels, moved the starters out of the way, disconnected a couple wires, did the swap and WALLAH! I don't get these all too often, but it's nice to get a "freebie fix" once in a while!

 

[seasick]

Just a follow up here...

Not sure if I had mentioned this, but when my brother and I bought the boat the owner had a spare engine (he said one cylinder was bad) that he gave us, which we picked up from him a few days ago. So last night I checked the stator (the two resistance checks) of the spare engine and it seemed good. I pulled the two flywheels, moved the starters out of the way, disconnected a couple wires, did the swap and WALLAH! I don't get these all too often, but it's nice to get a "freebie fix" once in a while!

That's great news and great diagnosing. Thanks for a very informative dialog.

 

[ocnslr]

On a related part of your post, the rough running on the muffs may be more noticeable than when in the water, but the OX66s are always a bit rough at low RPM.

The engine runs on four or five cylinders at RPMs between idle and about 2000. All that is by memory, as I sold the service manual when we repowered to twins in October 2005. Original engine was a 2001 250HP OX66.

 

[DennisG01]

Thanks, Seasick.

Thanks for the info on the rough running. I guess I'm just not used to big (and boy is it loud out of the water!) outboards.