1986 25 hp Mercury XD

[scurtis76]

Gentlemen,

I have an 86 25hp Merc XD long shaft that lost some power. It starts up fine but when I put in gear and go full throttle the engine sounds like she's moving good but just doesnt go full speed. Every now and again it will all of the sudden kick in and go full speed but that is not often. She started doing this half way through the season and as it progressed she basically stopped kicking in to full speed and just revs like its going. The prop spins and the RPMs seem to be good. I replaced the prop last season (2006) and the fuel filter and fuel line this season (2007). Any ideas? I'm in the SE Mass area and would love to get this engine up and runnig before the stripers start running. Thanks.

Steve

 

[jbjennings]

Re: 1986 25 hp Mercury XD

I'm almost certain (the way you described it) that you have a coil going out.
I have an '8425xd and had the same problem. Runs great now.
JBJ

 

[scurtis76]

Re: 1986 25 hp Mercury XD

OK. Im a novice when it comes to small engine repair so please talk to me like I'm 3.. What coil are you speaking of? Is it an easy repair with a manual? or should I bite the bullet and bring it to a shop? Thanks.

Steve

 

[jbjennings]

Re: 1986 25 hp Mercury XD

Well,
I'll give it a try.....your motor has 2 spark plugs, each plug has one wire and each wire goes to a "little black box" ---that is your coil(s). I suspect one of them is bad. You will have to determine which. You'll basically be checking for spark. You can find out by running it on muffs in the driveway. If you take the cowl off and let it idle and take one wire off with some good plastic handled pliers so you don't shock the crap out of yourself and if the motor dies, then the coil which that wire comes from is probably good and the other is bad. If you take it off and it has no effect, it MIGHT be bad. To be sure, put that wire back on and pull the other wire. If it dies when you pull the other wire, then the previous coil is for sure bad. I say "for sure" BUT there are other electrical devices that could be at fault. I just think that the coil is the most likely problem. You can order a coil online at iboats or other places and it's not that high. You'll have to get your serial number off the tag on the transom bracket to order it. It is very easy to change with simple tools. Anybody can do it. That being said, if you don't know where the coil is, it may be wiser to take it to a mechanic. It shouldn't be a high price if it is a coil to fix it, but if it isn't, a real mechanic's knowledge will save you more money than you will spend trying to replace parts trying to find out which part is bad. You should consider getting a service manual for your motor which is well worth its cost. Don't dare run the motor very long (more than a few seconds) with the spark plug wire off or it could ruin some expensive electrical parts. Also, I am not a real mechanic and changing a coil or cleaning a carb and changing the water pump impeller is about all I can handle on motors newer than 1977. So I hope you will keep that in mind when you read my post. AND----sometimes those coils will work, and then quit for no reason, which makes it hard to figure out which one is faulty. If yours only surges faster every once in a while, it should be pretty easy to figure out which one is bad. Myself, if I got obvious results when I tested the spark on the plug wires, I'd change out the coil that the wire with no spark came from.

Please keep in mind that I could be totally wrong and the problem may not even be a coil. It could be a bad spark plug. It may be fuel related (carburetor, fuel line, tank vent, etc.).

Here's a pic of my '84 25xd and it shows the coils which are where the spark plug wires are attached to. Hope this was helpful. Once again, you may want to go the mechanic route. ALWAYS smart if you are not pretty well experienced with outboards. I sure hope I haven't led you down the wrong path. Let me know what happens.
JBJ

 

[25_hp_xd_man]

Re: 1986 25 hp Mercury XD

Hey guys I am new to the forum. I really found this topic intersting b/c I am having the same problem. I was sure that is was my swithbox, so I ordered one off of ebay. It hasnt arrived yet. After reading the question and then the responce Im not so sure if I have made a wise decision. My motor is doing exactly what you described. And it is intermittent. I examined the coils and found that my bottom cylinder was dead. ( I did this in the method that you described above) I took a closer look at my coils and discovered a difference between the two. The one that wasnt firing properly had a fouled corner all the way in the back. I tried to clean it with a wire gun cleaning brush with not much success. I guess I am in the market for a coil or two now. I have had a hard time locating my serial # on these charts. My serial begins with A17. Look foward to talking shop with you guys in the future.

PS Its a 1985 mercury 25 hp xd(or at least thats what is stamed on the flywheel)

 

[scurtis76]

Re: 1986 25 hp Mercury XD

JB,

Thank you !! With that description I know enough about engines to know what I'm doing now. When you originally said coils I had no clue but your picture sure helped. I dont think it is a plug, fuel line, fuel filter or the gas because I replaced all that last season when this problem persisted. I think you hit the nail on the head with a coil and thats what Ill try first. Now as far as a good pair of rubber handled pliers.... can I get away with a thick pair of rubber gove? like the lobster guys wear in the winter or will I still get zapped?

SC

 

[jbjennings]

Re: 1986 25 hp Mercury XD

Yeah, I'd try it with the gloves. If it gets you I guarantee you'll find a way to "get loose"! I hope that fixes it but remember, I'm just an amateur at BEST!
Post back if you get it fixed...
LAter,
JBJ

 

[25_hp_xd_man]

Re: 1986 25 hp Mercury XD

Well guys,

You had me convinced that I had a coil going out. Wrong! I replaced the switch box and old mama rose is running like a new one. Just wanted to pass this bit of info along. Good luck.

 

[Magnum150]

Re: 1986 25 hp Mercury XD

You might check each coil to see if they are grounded properly, the intermittent thing sounds like a possible lose ground or a bad wire connection.