Seized 25hp 2-stroke

[xjma]

My brother acquired a 25hp 2stroke mercury that is apparently only a few years old (don't have the year) and has very low hours on it. Someone ran straight gas in it and it's seized. I've tried dumping oil down the spark plug holes, still not freeing up with the pull rope.

Question is should I try turning the crank with a wrench or just pull the head and see if the cylinder will come off the pistons??

We are hoping that a bore and some new pistons will bring this motor back to life. Are we wasting our time? Lower end spins just fine.

 

[Lubosleftboot]

Re: Seized 25hp 2-stroke

You will have to tear down the power head to ascertain where the seizure is. It could well be in the bores as you say but it may also be at the crankshaft main shells..If it is seized at the crank and has any bad scores in the barrels you would be best off finding another motor tbh.

LLB

 

[sutor623]

Re: Seized 25hp 2-stroke

My brother acquired a 25hp 2stroke mercury that is apparently only a few years old (don't have the year) and has very low hours on it. Someone ran straight gas in it and it's seized. I've tried dumping oil down the spark plug holes, still not freeing up with the pull rope.

Question is should I try turning the crank with a wrench or just pull the head and see if the cylinder will come off the pistons??

We are hoping that a bore and some new pistons will bring this motor back to life. Are we wasting our time? Lower end spins just fine.

Yeah plus the stopped making 2 strokes in 2006 or 2007, so it has to be at least 5 years old.....

 

[xjma]

Re: Seized 25hp 2-stroke

You will have to tear down the power head to ascertain where the seizure is. It could well be in the bores as you say but it may also be at the crankshaft main shells..If it is seized at the crank and has any bad scores in the barrels you would be best off finding another motor tbh.

LLB

How likely is it to have seized down on the crank bearings??? I'm hoping cylinders!!

 

[carholme]

Re: Seized 25hp 2-stroke

What is the s/n of the engine and why not tear it down anyway? You own it and may get lucky. Nobody can say what the problem is until you get it apart.

Gerry

 

[sutor623]

Re: Seized 25hp 2-stroke

RIght even if you part it out it will make you more $ than a parts motor.

 

[Faztbullet]

Re: Seized 25hp 2-stroke

Depending on the year it may be a scrap out motor. Only the blocks with the words Mercosil casted on the block is boreable if not it is a chrome bore and will need to be resleeved..

 

[xjma]

Re: Seized 25hp 2-stroke

where would I find the 'mercosil' cast?? Are sleeves available??

I don't know much about the motor other than it's got low miles, merc 25 stroke outboard with electric start and some kid that temporarily worked at my brothers job ran straight gas in it and seized it. It's been sitting around since then and despite his work having tons of boats and motors of all shapes and sizes, nobody there knows how to tear into them, so they just buy a new one. When I saw it it was ofcourse dusty but I would guesstimate based on looks of the housing that it is early 2000s ish vintage. Apparently it was on a boat that nobody liked to use.

I'll have to get the numbers off of it this weekend. I guess I'll just start tearing it apart and see what I find. Other than the lower end, what parts would be useful to people?? I guess if it's Fed the block could make a decent anchor for a jon boat or something, haha.

 

[oldman570]

Re: Seized 25hp 2-stroke

You can replace the powerhead, if you want to keep the motor, and use the needed parts from the old one. Check out the list of salvage yards listed on here, or ebay. If stright gas and no oil was used, the crank, bearings, pistons, and block are probley shot and can be sold along with the alluminim (SP) cans you collect while working on it. Isn't life grand Tee Hee. That way you will get some of your money back.Check out outboardexchange.com for a powerhead.
Oldman570

 

[xjma]

Re: Seized 25hp 2-stroke

You can replace the powerhead, if you want to keep the motor, and use the needed parts from the old one. Check out the list of salvage yards listed on here, or ebay. If stright gas and no oil was used, the crank, bearings, pistons, and block are probley shot and can be sold along with the alluminim (SP) cans you collect while working on it. Isn't life grand Tee Hee. That way you will get some of your money back.Check out outboardexchange.com for a powerhead.
Oldman570

With all due respect Oldman, I really do hope that you're wrong about the crank bearings, but I guess there is only one way to find out!! If the crank itself is fine (lower rod bearings OK) then it still shouldn't be too bad to fix.

Keep in mind the total cost into this motor so far is zero, so throwing 500 bucks of parts at it is still a good deal to for us (my brother and I). I enjoy working on motors, when I have the time.... This is just a 'hey, we can get this otherwise mint motor that is seized up for free, think it's worth messing with?' deal.

 

[sutor623]

Re: Seized 25hp 2-stroke

With all due respect Oldman, I really do hope that you're wrong about the crank bearings, but I guess there is only one way to find out!! If the crank itself is fine (lower rod bearings OK) then it still shouldn't be too bad to fix.

Keep in mind the total cost into this motor so far is zero, so throwing 500 bucks of parts at it is still a good deal to for us (my brother and I). I enjoy working on motors, when I have the time.... This is just a 'hey, we can get this otherwise mint motor that is seized up for free, think it's worth messing with?' deal.

Well he is saying that if oil wasnt used, then your s.o.l. Hopefully someone just ran the motor with a blown waterpump and the pistons seized up, but the crank is fine.

 

[xjma]

Re: Seized 25hp 2-stroke

My brother is pretty convinced that some 'summer help' didn't know the difference between 2 and 4 stroke and ran straight gas in it .

I know that with other 2strokes, straight gas doesn't necessarily mean the crank will be toast....I'm hoping here!!!

I really hate separate injection systems but in this case maybe it would have been better off....but then again, then I wouldn't be getting the whole outboard for nada.

 

[oldman570]

Re: Seized 25hp 2-stroke

Depending on what block you have, you could be in good shape. Blocks with chrome bores can not be bored out and have to be replaced if the bore is to scored real bad. You can sometimes lightly scrape the ammumin off a chrome bore and hone it and replace the pistons only if the crank and rod bearings are good. As for the oil injection, I would disconect it and use premix gas. That way you know it will get oil as the oil injection can and will go bad and you'll be back to square 1 again. Like I stated before, it is sometimes cheaper to just replace the power head with a good used one from one of the salvage yards. A good used powerhead shouldn't cost very much, as most dealers would rather sell new motors, rather than fix the older one and sell it, if the motor is 10 years old. At any rate the powerhead will have to come off and be split inorder to check the crank and bearings. Now you have a spring project, to keep you busy in your spare time, and you can end up with a motor that will last several years when done correctly.
Best of luck and Boating,
Oldman570

 

[xjma]

Re: Seized 25hp 2-stroke

I think they were running pre-mix in this one...which is how the kid that didn't know ended up running straight gas. I prefer pre-mix too, except for on snowmobiles.....hard to mix at a gas station.

 

[xjma]

Re: Seized 25hp 2-stroke

Depending on the year it may be a scrap out motor. Only the blocks with the words Mercosil casted on the block is boreable if not it is a chrome bore and will need to be resleeved..

So the motor is now in my back yard on a stand and ready for me to tackle it once I get the time. It's a 1998 model year, and the block says 'mercosil' so I guess it's boreable, which is a plus!!

I would do pretty much all the work myself other than bore/hone and redoing the actual crank and rods if that is necessary I'd have an experienced machine shop do that and balance it, etc. but other than that I can work on motors. It is a little different than a dirt bike or ATV motor....some of the **** I'm like, what is that, but I'm sure I'll figure it out once I rip it apart. Speaking of which I think I'm going to go pull the head off of it right now, so wish me luck fellas!! Thanx for all the help so far!

 

[Faztbullet]

Re: Seized 25hp 2-stroke

think I'm going to go pull the head off of it right now

That a water jacket.....

 

[xjma]

Re: Seized 25hp 2-stroke

Good news, the crank turns!! I'm about to go get a compression gauge, but from my thumb the top cylinder seems to have a little more than the bottom....hopefully the gauge will tell a different story. Going to pull the exhaust cover and see what I can see and use an actual gauge to get numbers, it could just be the way I'm holding my thumb. Either way, seems to have enough compression to run, so we will do a test run soon. Woo hoo!!

 

[xjma]

Re: Seized 25hp 2-stroke *Update* not seized up!!

Re: Seized 25hp 2-stroke *Update* not seized up!!

So, maybe I shouldn't have taken the water jacket cover off at night after a few drinks?? Too late now, I just realized that I broke two of the SS screws holding the water jacket on, and a third had already been broken, one that holds the water return fitting on there. It was somewhat drilled out and held on with a larger screw, so only holding that fitting on and not clamping it to the block A few of the screws that I didn't break came out with varying amounts of aluminum in the threads....hello thread chaser and anti-seize!! Wonder if the potential seize had anything to do with the stuck bolts??? Why SS on aluminum, because of the potential marine aplication?? This was to my knowledge only ever used in ponds and maybe a little brackish, but never out in the actual ocean. Oh well. I'm better at taking steel screws out of aluminum on say dirt bike/ATV motors....live and learn, again.

I was planning on popping off the exhaust cover (or what I assume covers the exhaust, large cover plate covering side of both cylinders on port/tiller side of motor) so that I could get a look see at the pistons and the rings, but the two middle screws are pretty stuck and I don't want to be extracting any more!! All of the outside screws were way loose. This doesn't appear to have been messed with since factory assembly as the SS screws had the factory black paint on them with no scratches or indication of being worked.


SO, what's the best procedure for extracting stuck SS screws from aluminum block?? Apply heat (I have MAP gas, no oxy/acet, but could borrow some), cool with PB/WD, and give er a try?? Luckily there is enough of each screw protruding that I can get them with a vise grips. It would REALLY suck to have to try to drill these SS screws out!!! Would I be even more screwed if they were steel fasteners instead of stainless??

Should I replace with SS fasteners or mild steel?? I'll use the good anti-seize during re-assembly!!

My brother was hoping to come over today with the gas can and see if we could fire this puppy up....hopefully we can get the jacket on good enough so that we can at least get a test run in...with water leaking all over the place. I'm sure that will be fine, no??

Will chasing threads with a tap and using anti-seize be fine, or do I need to heli-coil some of these?? Is this normal for so many stuck screws??


thanx for all the help!!

 

[carholme]

Re: Seized 25hp 2-stroke *Update* not seized up!!

Re: Seized 25hp 2-stroke *Update* not seized up!!

Way back when I asked you for the s/n it was for a reason, so we could get you the service manual online and the parts listing. We don't even know if it is a 2/3 cylinder.

There is a difference between being a bull in a china shop and being patient enough to try and salvage the engine. I still can't believe that you are so anxious to run this thing. At least getting the exhaust off you can have a look and feel to see if the rings are frozen or broken.

Have you at least dropped the LU to see the condition of the impeller before running it?

The wisdom of others on here would have shown you to soak, heat and tap the screws, gently working them to avoid breaking as many as possible.

However, if you must run it, go ahead, maybe you can succeed in damaging it even further!

Gerry

 

[sutor623]

Re: Seized 25hp 2-stroke *Update* not seized up!!

Re: Seized 25hp 2-stroke *Update* not seized up!!

Chasing threads often works fine. You can send pics if you'd like. If the head is not down tight, with a fresh headgasket, water will not only squirt all over the place, it will find its way into the cylinders. Just do it the right way and wait until you get the head back on before trying to fire it up.