Mariner 25 gummed up plugs

[superkrusty]

Re: Mariner 25 gummed up plugs

After soaking some wd-40 in both cylinders last night it finally free'd up. Tonight I finish putting together and hopefully she is a goer !!

Thanks for help everyone , hopefully able to post a pic of motor running and me smiling

Cheers

Brad

Or the gearcase has rusted and seized.

If you haven't rebuilt the water pump now would be a good time to drop the lower, then see if the motor turns.

 

[wrench 3]

Re: Mariner 25 gummed up plugs

After running it for a bit, you might want to do another compression test to make sure there was no permanent damage to the cylinders or rings.

 

[superkrusty]

Re: Mariner 25 gummed up plugs

#$%#@%# Back to the drawing board.

Assembled motor , ran (a bit rough but was running ok) , ran for five minutes but still water gumming up in the spark plugs.

Back to where i started now. Did another compression test with about 140 PSI in top cyl and 105 in bottom cyl. Both went up about 30 PSI with a wet test.

Is the next step to pull the head off ? After having all the trouble with the exhaust cover bolts are the head bolts going to give me the same grief ?

Thanks in advance

 

[emckelvy]

Re: Mariner 25 gummed up plugs

#$%#@%#

Is the next step to pull the head off ?

After having all the trouble with the exhaust cover bolts are the head bolts going to give me the same grief ?

Thanks in advance

Q1. Yup.

Q2. Very Likely. Go slow and heat carefully along the side of the head where the bolt goes thru. Most of the time the bolt gets seized into the head, but it's also possible to seize at the block as well. Run the flame back & forth along the bolt and when you get the part that's stuck hot enough, you'll feel the bolt start to give.

If you get to a stubborn one, leave it be and go to the next one. By the time you get done, it's likely that all the heating done to the head will help release the bolts previously stuck.

And don't just replace the head gasket; since you have a water leakage problem the head is probably warped as well. Have the head surfaced at a machine shop, or if you have lots of time and a nice flat surface (like a pane of glass or big metal plate), surface the head with sandpaper between head and flat surface.

HTH & G'luck........ed

p.s. a few years back I worked on an 8hp Mariner with a badly corroded mid section, I had good luck finding used replacements on eBay.

 

[CharlieB]

Re: Mariner 25 gummed up plugs

AAAAAAAAAAA, that isn't a head, that is a water cover gasket.

You would be better off the pull the powerhead off, rig a seal plate to the bottom, drilled and tapped for a line into the water inlet and pressure test the block.

Usually we find a faulty seal on the exhaust side, but sometimes a cyl liner will turn/shift and fail to seal allowing water to enter a cyl at a port.

Assembling the exhaust side using any sealant while wet can allow a gasket to squeeze out like a tiddly-wink and cause a leak. Either assemble dry or use any sealant as absolutely thin as possible and wait until it is dry before assembly.

It's a P.I.T.A. to have to take it apart again, but necessary.

 

[superkrusty]

Re: Mariner 25 gummed up plugs

I took off the exhaust cover and cut a new gasket and installed. Leaked again.

I have taken the head off , as I have never seen one of these before does it look normal ? There seems to be a sleeve half around one cylinder and completely around the other one ?

 

[Bosunsmate]

Re: Mariner 25 gummed up plugs

Thats not a well looking cylinder block. They should be complete around the cylinder. Your head gasket wont be able to seat on that

 

[CharlieB]

Re: Mariner 25 gummed up plugs

O.K., it DOES have a cyl head instead of a water cover.

This is a Yamaha marketed by Merc.

Sorry, but this block is done.

Too much salt water use without flushing after each use explains the exhaust bell corrosion and this erosion around the cyl liners.

You may get lucky and find a usable block, either Merc or Yamaha 25 HP of the same early to mid 80's from one of the inland marine salvage recyclers at a very reasonable cost.