1986 Mercury 25XD - Multiple Failures Occuring

[CrappieChasingCajun]

1. Boat purchased this year and was running fine on electric start or pull start (I tested before and after purchase on hose and in a small lake).

2. Previous owner informed me before purchase that the boat was not starting this year but he had it worked on by a mechanic and had the CDI box replaced and carb cleaned thoroughly.

3. Issue happened when trying to launch the boat the second time. Boat would run for 5 seconds or so on idle but then die when using the key - electric start. After 2-3 times trying this (waiting about 30 seconds between tries) the electric start stops working completely and I just hear the solenoid click. So I go back and try to pull start, engine starts up for 5 seconds or so then stops. This motor has a little choke button that if you press it it'll push fuel into the carb. I could keep the motor running by pressing that but didn't want to mess up anything so I gave up for the day. (*Sad 3-year old that day, she has still yet to catch her first fish)

5. I contacted the previous owner's mechanic who said it sounded like two separate problems - solenoid & carb gunked up.

6. Replaced the solenoid and got a rebuild kit for the carb and replaced gaskets. The carb looked sparkling clean when I pulled it off but I cleaned the heck out of it with air and carb cleaner hitting every little thing 3 times at least. The fuel diaphragm looked a little worn but no cracks/tears. The rebuild kit had a new one so I replaced that and the paired gasket too.

7. I also checked a lot of the common things (or so the internet has told me they are common). Shifter is in neutral (solenoid wont click when it's not in neutral). Kill switch is off, it's in run firmly. I had brand new non-ethanol gas an 50-1 oil but I changed it with new gas from different station just to eliminate that as a possibility.

Attaching photos of the motor from all sides. Any help/advice is appreciated as right now I'm about ready to just take the kiddo out using the trolling motor alone.

 

[CrappieChasingCajun]

Thought of one more thing. After it wouldn't start at the boat launch I checked the gas tank vent. It was half gunked up so I cleaned it but still couldn't start it without mashing on that choke button. It will run with that pushed though.

 

[merc850]

Where did all that mud come from, was the motor submerged at any time? It looks like the water jacket around the Nr. 2 cylinder is cracked which would suggest freezing water. Did you check the compression? Tip the engine up and push the primer which will let fuel flow out of the carb, if it doesn't then you still have a supply problem. Did you clean/replace the fuel filter (big yellow thing at front)?

 

[CrappieChasingCajun]

Thanks for responding!

The mud is dirt dobber nest remnants (louisiana). Was a bit surprised that the previous mechanic didn't clean it up better but that's for sure what it was. Still had some dried up larvae around the base.

I'm not sure how to test compression but at first glance it looks like another trip to harbor freight is in my future. I'll research tonight and report back on the test results tomorrow.

I cleaned the fuel filter well and got another one ordered to rule it out as a suspect. If I disconnect the fuel line from the carb and squeeze the bulb I get gas flowing well out of the line.

I'll tip it tomorrow morning also and verify that fuel flows out of the carb when I press the primer.

 

[flyingscott]

Your motor has been severely neglected. There are parts.missing off of the front of.the carb. Start with a compression and spark test if those are good rebuild the carb. Then put in a new waterpump. You need.to clean the carb completely preferably soak it.

 

[CrappieChasingCajun]

Thanks I have a compression tester now and will test it as soon as the rain lets up (probably Friday). when you say test spark - you mean with a normal auto spark plug tester?

I did clean the carb with a compressor and carb cleaner but have not soaked it. Will try that next.

This boat belonged to a guy that lived on a bayou and the boat was tied up to his dock almost year round so I figured it would have some issues and worked that into the price. ($1500 for boat/motor/trailer)

Thanks everyone for all the help. I'll report back when the rain stops and I can work on it again.

 

[scout-j-m]

What compression tester did you purchase? I have 3, one of which is a harbor freight one. The Harbor Freight one reads prob 2/3 the compression the other two do. It works to verify consistency between cylinders but I don't trust it for much more than that. I got an Innova brand one at Autozone for $30, and it serves me well considering the cost.

Autoparts stores also have the type spark tester you need. Get the kind you can adjust the gap on. Most of my motors will all jump spark across a 3/8", if not more, gap.

 

[CrappieChasingCajun]

I bought the "Maddox deluxe" compression tester after reading people's reviews about the cheaper one at harbor freight. Hopefully it will give a good reading but if not back it'll go. At the very least I'll know if there's a big difference in compression between valves - which is apparently bad news.

Thanks for the heads up about the Innova brand one as a backup. I'll swing by Auto zone and get a spark tester like you mentioned also that can do gap adjustments.

Thanks again everyone, I might make crappie spawning season yet!

 

[racerone]

There are no " valves " in the cylinder that have anything to do with compression.

 

[CrappieChasingCajun]

My mistake on the valve comment. This is all new to me and the only time I've tested compression on anything before was my grandpa's old ford pickup where the end comment from him was "the valves are done up".

Rest assured I'm following along with videos and other guides for anything you guys say to make sure I don't make a bigger mess of this motor.

**FlyingScott I just noticed you mentioned that parts were missing from the front of the carb. Any critical parts missing I should be worried about?

 

[CrappieChasingCajun]

Reporting back in. Sparks are both blue and jumping every time. I disassembled and dipped the carb overnight Friday, cleaned thoroughly and put back on today but no luck.

Compression test using the Innova brand tester (thanks scout-j-m):
1st test: 110 PSI
2nd test: 115 PSI

Not sure if that difference is bad enough to be trouble?

I keep feeling like the starter not engaging AND the motor not pull starting going wrong at the exact same time points to an electrical issue so I cleaned the terminals today and replaced one connector that was damaged - but still no luck.

I bench tested the starter and it works so something still wrong elsewhere.

Planning to multimeter test wires tomorrow but if anyone has other suggestions please let me know.

Thank you everyone for the guidance so far. I feel much more confident tearing my motor apart now than I did a few weeks ago.

 

[flyingscott]

The fact that you have to push the primer to keep it running points to a plugged carb. You need to soak the carb and rebuild it woth a quality kit that includes fuel pump and primer. The parts that are missing are the primer button assorted linkages and a carb cover up to you if you want to replace them.

 

[CrappieChasingCajun]

Thanks for the heads up on the missing parts.

I did soak the carb for 14 hrs in the dip stuff that comes in a big paint can looking bucket. Also recleaned with air compressor and wire jet cleaners.

New development today - I got the starter working!
(Boat still not cranking though)

I took the solenoid off again and put new connectors on two wires that looked rough (you can see in the old pics the starter yellow wire was particularly rough). That did it!

I will pull the carb off again though and soak it again. Like you're saying it's all that makes sense. Can I soak it too long? Was thinking a whole 24 hours with me giving it a shake once in a while.

My rebuild kit came with a bunch of stuff that I replaced - the little primer pin part, fuel diaphragm, and all gaskets.

 

[CrappieChasingCajun]

24 hours of soaking, rinsed and blew it out with air again also, think I've got the cleanest carb in the state now.

So take a look at this picture - the diaphragm & gasket are in reverse positions from what was on my carb when I got it. I took pictures when I originally took it apart so I could get it back together correctly but I'm hoping this might be the core issue.

Will change it over tonight when I put it back together and let y'all know how it goes.

 

[Texasmark]

Your compression numbers are ok, differences are ok too. Is your battery fully charged and is it new or have you had it load tested? Have you removed the connections on the battery leads (at both ends) and cleaned the mating parts of the terminals and reconnected good and tight?

Let's look at something else. Does the squeeze bulb pump up firm prior to engine starting? Do you have any fuel visible around ANY of your fuel lines which would indicate replacement? Disconnect the fuel line at the carb and using a suitable container spin the engine and check for fuel delivery. Results?

 

[CrappieChasingCajun]

Motor is running!!

I believe there were three core issues:

1. Previous owner's mechanic put the gasket/diaphragm in reverse order on the carb and I kept putting them in those spots after cleaning/rebuilding the carb each time.
2. Many terminals and wiring were bad.
3. Starter solenoid went bad.

This was tough. Probably tested my patience more than I have in a long time and I almost gave up and took it to a mechanic but glad I didn't.

Thank you to everyone on the forum that replied!