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2000 Sportster 1800 all of a sudden cannot accelerate

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megerian

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Hi - I was boating all week with no issues. My boat has given me no issues at all over the years I have owned it.

Two days ago, after about an hour long ride, I go back out to start her up, and she immediately sounds terrible. Barely starts, dies, rough idle. The only way I can even get the boat to move at all is to start it up, then before it dies, move the selector from Neutral to Forward, then give it gas. Then she still only goes up to about 10 mph, and will not accelerate past that.

I putted around the bay for a few minutes to see if anything would happen, and twice the engine surged like everything was fine, but then went back to running rough. I went back to the dock, and a guy suggested changing the spark plugs. I changed all 6 plugs and it made no difference. Its got fresh gas and fresh oil. I also check the fuel filter and its fine.

Any ideas?



IMG_0287.JPGIMG_0288.JPG
 
The first thing I would do is find out which cylinders are firing. If you have an inline spark tester, that will certainly tell you a lot.

While you are in there, check to make sure all of the wire connectors are all good, look for cracked wires, connectors that might have got pulled apart.

The next step would be to check your compression. If you have a compression tester, that will also guide your diagnosis to what might be the issue.

Once you get those pieces of information, post it up in here, I'm sure DrHonda will chime in and take you to the next step.
 
All of the above is a good place to start.

I always suggest a compression test, just for knowledge. In your case... I don't think it will be a problem, since it's still surging up to full power.

To me... this sounds very "Electric". I think you are losing a couple cyl's. SO... checking for spark is a good place. As Henry said... get a couple in-line testers, hook them up, and start the engine. The reason you need an inline tester is... you need to know if the engine is running rough, or smooth.

Also... with that... look around the helm electronics, and look for a small black box. If you find it, note the numbers printed on it. If you have a throttle guardian... we need to remove it. (it will cause issues just like this when they go bad) But... since they are such a pain... most of the time they have already be ripped out by previous owners.
 
Thanks for the tips, I have a few follow up questions. If I use the spark tester and find that some of the cylinders are not sparking, what will be the next step?

Also, when you mention the small black box, it reminded me of a little box attached to the engine right after the fuel filter. I have attached a photo. What is that thing? It seems like I heard it clicking when I was starting the engine. Also, just for the heck of it, I disconnected it from power but that made no difference.

thanks!!

boat.jpg
 
update - got an inline spark tester, and one whole side (3 cylinders) does not light up. What next?

Also, this was strange, but when I started on one side, the engine would fire right up and stay running for a few seconds. By the time I got thru checking all 6 spark plugs, the engine would no longer start or stay running.

Also, as I mentioned earlier, I hear a clicking sound that I don't think I heard when things were running well.
 
Well, for sure it is electrical. I don't have my Mercury Service Manual handy, figures the one weekend that I don't go up to the cottage!

But if you have a whole bank of cylinders not firing it is either your stator or one of the Switch boxes. DrHonda will chime in with the next steps.

I had almost the exact same issue, one thing to note, if you have one switch box go out on you, you need to replace both... According to Mercury. Although the Dr has said that he has seen many cases where replacing one will work. I tried replacing one, it got me through to the end of a season, but the other needed replacing at the start of the next season! However mine situation may have been complicated by a faulty stator at the same time?
 
Regarding your throttle guardian... I don't think your boat has one (mine doesn't)... But either way I think they are up in the driver helm area.
 
Well you can dig up the part number and search for one on eBay. Make sure you are getting an OEM Mercury part, after market will not do the job. Or just drop in st your local authorized Mercury Marina, they can order the part for you... Try and negotiate a discount, they have a huge mark up.

Before you order parts, I would talk to the Dr one more time just to be sure there is something more you should check.
 
Okay, I tried to use the parts diagram on this website and didn't find a switch box, but I probably wasn't looking in the right place. Henry, it looks like we have the exact same motor, I am not sure of the difference between your Challenger 1800 and my Sportster 1800.
 
From the service manual... Go to page 1C-7, look at item "f"... They are the switch boxes.

They are mounted directly on top of one another.
 
Since you have a 210 engine... when you loose an entire bank... that's the switch box. But, check the stator too. (and the wires coming out of the flywheel)

The last picture you posted is the lift pump, and the relay that turns it on and off.

The throttle guardian will be up in the helm, if you have one.
 
Can you give me more info on how to "check the stator". I have no idea what that is, what it looks like, or how to check it.

In the diagram linked by Henry, there was a switch box in the picture, but I do not see a stator. Any links or photos, or pointers to related posts would be most welcome.

Thanks - and ballpark estimate - whats a switch box cost?
 
The stator is the "Generator" unit that is under the flywheel. Normally, you will pull the flywheel to get a visual. (scrapped wires, burnt looking insulators, so-on) Then, you will pull it's connector, and check it with a meter. You will look for a short or a ground.
 
Yep, when I was investigating the same issue on mine, I found it seems fairly typical they last 10-15 years. That's why it's important to check the stator, they have about the same life-span?
 
So, one thing I was thinking of.. are the switch boxes interchangeable? Meaning, can i reverse them, then if the right bank of spark plugs stop firing, then I know its the faulty switch box? I am trying to narrow it down. If i can be sure its the switch box, then I can order two replacements, and for $600, i am back on the water.
 
Well, that is a good question, as far as I know the part number is the same for both... So yes in theory that should be a good test.
 
Well - I dove in yesterday, those switch boxes are not easy to access or remove, but I made pretty good progress. henry, did you swap these out before in your boat? The question I have is about wiring. There are about 6 wires coming in, and 3 wires going out, once you were able to disconnected the switch box, was it fairly straightforward to wire the new one in?
 
My issue had a combination of switch box failures and stator failures, so I brought it into a shop to do the final diagnosis and they did the installation of the parts.

Fortunately, Mercury was very generous and because this was the 2nd time I had it into a shop for the same issue in less then a year, they covered the labour charges as well as one of the switch boxes that I replaced the year before! So I only had to pay for 1 switch box and the stator.
 
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