mercury 45hp 4cyl ,block seal leak

[scrapper042000]

i need an opinion guys ,I have a boat in the shop with a 45 hp merc 4 cylinder (1986) ,owner said the boat would bog down and run rough at times ,while checking the motor I sprayed carb clean along the left side of the engine block at the split where the 2 block halfs join as I spray carefully on the seam the motor bogs down and will kill ,I put some rags to avoid drift to the carbs and no matter how carefull I am. it is definitely drawing air in at the block seal ,my opinion this motor needs to come apart ,I also notice no spark at #2 cylinder (presuming switch box ) I just feel the motor should come apart because of the crank case drawing air ... any opinions guys ?

 

[emckelvy]

Sounds like you've got it figured out! It needs to come apart and be re-sealed with Permatex/Loctite 518 anaerobic sealer. Sold with primer/cleaner called "Mercury Master Gasket" kit. But if you clean the crankcase halfs carefully and degrease, the 518 alone will do the trick. Lots of times you can find it at NAPA and other auto parts stores. A little bit goes a long ways!

BTW if you're gonna do a teardown, the crankshaft/rods/pistons rotating assy should be pulled from the block and both inspected for damage. I would throw-in a new set of rings and crankshaft seals just for G. P. (General Purposes)!

G'luck with the repairs........ed

 

[scrapper042000]

I agree with you the not my favorite part of the motor ,(splitting them )yep go overhaul or nothing being the block is leaking ,I tested it four times to make sure ,and we both agree a block sucking in air wil never never tune or run correctly ,just wanted to make sure before I call this guy .he has had a few marine shops work on it from the classic rebuild the carbs trick to new coils ,lol unreal .....I just cant ignore the leaking block and I did not see any bleed off lines to crankcase anywhere near where I was spraying it and the throttle shaft pivots on a bracket isolated from the block ....and tried to be very carefull about drift from the spray into other areas ...I couldn't believe how I could make the motor die from the spray that easily ,thank you ed p.s. one im not sure how many other people have had a leaking block seal and never knew it..

 

[emckelvy]

Haven't seen too many newer motors leak like that, but a lot of the older 50's 60's develop leaks 'cause they used to use Permatex or similar gasket sealer, this degrades over time and then you get bubbly's out the crankcase halves!. The 518 anaerobic sealer should last the life of the motor.........

http://www.napaonline.com/Catalog/C...kel-50-ml-Loctite-518/_/R-NCB37394_0452185237

 

[racerone]

Leaks there are quite rare on a properly assembled motor.---Any evidence this motor was apart before ?

 

[scrapper042000]

the motor looks clean and low hours very above average ,even the decals ...all the oem paint is on the block bolts where it splits no matter how carefull I try I can still kill the motor by spraying on the seam ,theres no way I want to send this one out from what I am seeing ....I don't want to be the well lets try this person on this outboard ...when I ran a comp test one of the cylinders did have a milky looking crud that came out of the spark plug hole while turning it over ....I am going run this thing one more time and call the verdict ......I did have an old merc 85 hp do this once as far as a leaking crankcase ,was hoping I wouldn't see another one ,that motor ran different everytime you started it ,poor idle and a dead spot until you could coax it up to plane if I didn't kill and very hard to start which was most of the time ....its funny how some of the very dirty and greasy looking motors ive seen ran awesome and some of the cleanest ones ive seen are blown up or scored pistons lol