# My 95 Mercury 25 hp, blew up today. Happy Father's Day!



## fakirone (Jun 15, 2014)

Long time lurker, but first time poster. I was planning on waiting and having my first post document the restoration I am currently doing on my skinny boat, but today changed that. 

I was running my Alumacraft 1442 NCS upriver with the family today when a log made it past my prop guard and bent my prop. It was causing some minor vibration, but since we were about 1/4 mile from the sand bar we were headed to I decided to try to push on. Big mistake. I do not know if the two things are related or not, but about two minutes later a huge puff of smoke comes out the engine cover and the engine dies. That was that for the 2 stroke and we were stuck on the trolling motor to head back. 
When I got home I pulled a plug and tried to crank the motor, turn over ok. Put the water muffs on the I take for a few minutes and started seeing a little seepage around the bottom cylinder head. 

Long story short, I'm SOL. :-(


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## fakirone (Jun 15, 2014)

A. Does anybody have any ideas what the issue may be?

B. Does anyone on this forum know a good TRUSTWORTHY marine mechanic in the Atlanta GA area?


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## Y_J (Jun 15, 2014)

Which part of the Atlanta area you looking for? I'm kind of looking for something in the west (Carrollton) but not found one as yet. Let me know and I'll re-double my efforts on a wider scale at looking.


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## fakirone (Jun 15, 2014)

I'm in Roswell, but for the right mechanic I would drive. So pissed my new boat is dead.


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## fakirone (Jun 16, 2014)

Okay, after carful thought and consideration over the last 24 hours, I have come to the conclusion that my water pump/impeller must have failed or some other failure causing my motor to over heat. The power head was EXTREMELY hot and there was smoke or steam coming from the top end when it quit. 
So did a compression check, bottom cylinder is kaput. Any of you guys think that this might be just a cylinder block gasket and or cover?

Plug on the right is from the bottom cylinder






Top cylinder





Bottom cylinder





Any ideas as to where I should start? I have been searching online and here, but have been unable to find much info.


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## SumDumGuy (Jun 17, 2014)

pull the head and check it out. if you're lucky there will not be a lot of damage and you can replace the gasket and lap the head (hopefully!!!).


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## jethro (Jun 17, 2014)

I've burnt down engines on snowmobiles dozens of times and I got to say, that plug doesn't look bad at all. And if you can pull it over that is a good sign. All you can do is start pulling parts and checking specs. If you melted a piston you probably wouldn't be able to pull it over and your compression test shows some compression at least.

Even if everything looks good and it just seems like a base gasket, DO NOT put it back together without having a machine shop check the barrels for warping. You can easily make a bad situation much worse by running a warped head. I learned that the hard way.


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## fakirone (Jun 17, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=356105#p356105 said:


> SumDumGuy » 17 Jun 2014, 13:56[/url]"]pull the head and check it out. if you're lucky there will not be a lot of damage and you can replace the gasket and lap the head (hopefully!!!).


I am praying!!!



[url=https://www.tinboats.net/forum/viewtopic.php?p=356117#p356117 said:


> jethro » 17 Jun 2014, 14:43[/url]"]I've burnt down engines on snowmobiles dozens of times and I got to say, that plug doesn't look bad at all. And if you can pull it over that is a good sign. All you can do is start pulling parts and checking specs. If you melted a piston you probably wouldn't be able to pull it over and your compression test shows some compression at least.
> 
> Even if everything looks good and it just seems like a base gasket, DO NOT put it back together without having a machine shop check the barrels for warping. You can easily make a bad situation much worse by running a warped head. I learned that the hard way.


I was thinking that I will check the cylinder bore for round and scoring, if there does't appear to be any damage replace the cylinder cover (head) and gasket with a new one, then go from there. I am hoping that it's not unreasonable to hope that the rest of the power head is in okay shape. 
It definitely cranks easily so there's no lock up, and considering there's as much compression as there is I am hoping it's just the gasket and cover. [fingers=crossed] [/fingers]


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## turbotodd (Jun 17, 2014)

Need to pull it apart and inspect. My guess is that mercosil (if it's a mercosil 25...I don't remember when they got mercosil) got you during the overheat. Mercosil is a trade name for a plated cylinder-meaning it's not really "hone-able"....but there are companies that will bore/sleeve it which is a better option anyway.

used to, Merc made a kit to re-do the powerhead. Block, pistons, gaskets basically, and you re-use your existing crankshaft/rods, etc. Don't know if they're still doing it or not? Have to call Merc to be sure.

Mercosil 25 hp motors are famous out here in the duck woods. Lot of guys hate them with a passion, some still have them and 1 or 2 have been sleeved. The sleeved ones were done because nobody else makes a shift-in-the throttle motor, which apparently the duck hunters seem to like.

They are blind cylinders, IIRC, meaning the head doesn't actually come off. There is a cover over it, but you can't get to the pistons. The entire block has to be removed from the leg and then split, remove the crank, rods, pistons as an assembly from the bottom of the upper crankcase. If the cylinders are damaged/scored, it either should be replaced or send it off to the right people to have it bored/sleeved. Last I checked (which was many years ago), a place in Michigan did just this...usually around $400 back then.

Some of it going off of my ailing memory-so it's entirely possible that I'm out of line; and I look forward to any correction.


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## crazymanme2 (Jun 18, 2014)

I believe those are chrome bore cylinders.


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## fakirone (Jun 19, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=356181#p356181 said:


> turbotodd » 17 Jun 2014, 23:47[/url]"]Need to pull it apart and inspect. My guess is that mercosil (if it's a mercosil 25...I don't remember when they got mercosil) got you during the overheat. Mercosil is a trade name for a plated cylinder-meaning it's not really "hone-able"....but there are companies that will bore/sleeve it which is a better option anyway.
> 
> used to, Merc made a kit to re-do the powerhead. Block, pistons, gaskets basically, and you re-use your existing crankshaft/rods, etc. Don't know if they're still doing it or not? Have to call Merc to be sure.
> 
> ...



Yup, tore it apart today and the power head is exactly as you said. Damn near impossible to look into the cylinders. I stopped short of pulling the bottom end and taking the crank out because I think I've found the problem.
Both the cylinder cover and the exhaust cover had bolts that were loose. In fact the exhaust had two that weren't even finger tight. I looked through the exhaust ports while turning the motor over, everything looks fine. No scoring on the sides of the pistons, rings or the cylinder walls that I could see. Pulled the carb and reeds, the rods and crank looks fine. I really feel that I may be okay.
The thermostat looked like complete hell and I would bet it was my issue. In fact all of the cooling system is a mess. Must have been ran in some hella dirty water sometime in the past.























I would be putting it back together tomorrow if not for a few little issues. First, 6 stinkin bolts broke coming out. 3 in the exhaust side and 3 in the cylinder cover. So frustrating. So those need to get taken care of unfortunately.
Also, I found this sitting on top of the reeds while disasembling the motor. Any clue where it goes, cause I have no idea.


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## fakirone (Jun 19, 2014)

Not sure why the pictures were not working, but they're fixed now. Anyone know what that little spacer is?


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## earl60446 (Jun 20, 2014)

6 busted bolts, that sucks. I guess you are gonna be pretty good at drilling out broken off bolts by the time your done. I looked at some online parts fiches and did not see that spacer you found. Wish I could help ya. There are some utube videos with tips on removing busted bolts, best of luck. I usually use anti-seize when I put bolts back in, on spark plugs too.
Tim


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## fakirone (Jun 20, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=356446#p356446 said:


> earl60446 » 20 Jun 2014, 11:45[/url]"]6 busted bolts, that sucks. I guess you are gonna be pretty good at drilling out broken off bolts by the time your done. I looked at some online parts fiches and did not see that spacer you found. Wish I could help ya. There are some utube videos with tips on removing busted bolts, best of luck. I usually use anti-seize when I put bolts back in, on spark plugs too.
> Tim


Is it possible that this thing was just sitting in the area between the reeds and carb while the motor was running? That would be crazy.

and yes, 6 busted bolts sucked, as did drilling them all out. WHAT A PAIN. I bought all new bolts for both the exhaust and cylinder cover. The old ones obviously weren't doing so hot. I also have tapped all the holes to clean them up and will definitely be using anti seize.


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## earl60446 (Jun 20, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=356484#p356484 said:


> fakirone » 42 minutes ago[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=356446#p356446 said:
> ...


You must be the king of busted bolt removal if you got them all out already. Good job.


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## fakirone (Jun 22, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=356488#p356488 said:


> earl60446 » 20 Jun 2014, 18:54[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=356484#p356484 said:
> ...


they're all out, but it certainly wasn't easy. Starting reassembly tomorrow. [fingers=crossed]


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