Mercury Mariner 110 9.8HP Full Rebuild Advice

[lonestar65]

I'm in the process of rebuilding a new to me 1985 Mariner SN 0A143401. It had not been ran for years when I got it, so I replaced the water pump and I was able to get it started. After about 30 seconds of full throttle I started getting exhaust out the tell tail. I started this project with the intention of replacing gaskets and now I have the complete power head tor down. I'm new to outboards, I've rebuilt several car engines but nothing 2 stroke. As you can see in the picture the cylinder walls are nice and smooth but the pistons and rings are ruined. What causes this type of failure? There is play in the rod bearings, could that be the cause of the damage? Can anyone direct me to a rebuild manual with proper torque specifications?

Lastly for those with years of experience on the Mariners is there any Sage like wisdom you can provide me with? Other trouble spots to watch out for - I know the crank shaft on these is subject to failure. Any parts I should replace even if they pass visual inspection? I was planning on buying all OEM parts from https://www.mercruiserparts.com/7-5-5206550-up but they don't offer a complete rebuild kit. Is there a OEM suppler that does?

Thank you,
Justin

 

[racerone]

I do not believe that 9.8 was ever marketed as a " Mariner "---------Have you honed / measured the cylinder bores , yes or no ?----Perhaps hone the cylinder and examine the bores.-----How much play is there in the rod bearings ?-----The water pump impeller is iffy on those and needs to be replaced every 2 years.------Damaged caused by overheating !!----How did you determine that crankshaft is " subject to failure " on these.-------Oh----I own more than 1 of these 9.8 motors.----Have had more than one apart too.

 

[lonestar65]

My apologies, the previous owner had told me the 110's were Mariners??? I have not honed or measured the bores yet, I can't get access to a bore cylinder gauge locally so I'm at a standstill on that. I've called several small engine repair shops but non of them measure cylinder bore. The local marine wan't $200 to measure the bore, which is ridiculous as that's about what a decent gauge runs. Road bearing play is basically zero in the direction of piston travel but the left to right play is quite a bit, replacement bearings are cheep at under $5 a piece so I'll go ahead and do that while its apart. As for the crankshaft I had come across a few posts talking about crankshaft failure.

p.s. It's good to speak with someone who has experience with these motors

 

[racerone]

??----Side to side play on the rod bearings does not matter.----The previous owner does not know.----I have seen broken cranks on these but it is not common.----Shops are busy and do not want to be interrupted by a " no profit opportunity " type job.----A basic cylinder hone is about $40.00 and a good investment.----Where do you get replacement bearing for rods at under $5.00 apiece.------And are you aware that the rod bore and crank journal are part of the precision bearings ?

 

[lonestar65]

You are correct about shops not wanting to take on a low $ job. I have a cylinder hone but I don't have a cylinder gauge.
Yes I'm aware the rod bore and crank journal are part of the precision bearings, mine appears to be in good shape. I'm referring to the rod bearings #16 in the diagram.

 

[racerone]

5 seconds with a hone in a cylinder ( 3 stone type ) will show score marks.-----You have to do that.----There has to be side to side clearance.----Motors are assembled with parts that are cold.----But with an aluminum block and a steel crankshaft the parts change dimensions at a different rate as motor warms up..