i have a 2006 90 hp mercury two stroke, it always ran great. last week while going down the lake it just shut off. like it ran out of gas. when it stopped i fired it back up. it planed off ran great for about two minutes, same thing, shuts off again, fires back up runs great for another 2 minutes. it did this all the way back to the boat ramp. took it home changed fuel filter, changed pump up fuel bulb, changed plugs. went back to the lake, fired it up runs great. only now it has this knocking, rattelling, pecking mixed up sound. coming from the bottom of the motor and the top of the shaft. are their any way to know if its a rod or bearing problem, with out tearing down the motor. and also standing behind the motor, i can push the prop in and pull it out about 1 inch, and the nut that holds the prop on is tight. is this normal. it could be thisthing is going bad somewhere. but i thought it may be a motor rod bearing because the noise started after it shut off. any one thats had this problem and can tell me whats making this noise, i sure would be thankful. waterdog

From your posting several things could have occurred:
1) Engine ran lean from fuel restriction damaging a wrist pin or rod bearing
2) Lean mixture damaged lower bearing
3) Lower unit has a problem

The play in lower unit if 1 inch is a problem but up to 3/8inch in/out play is normal. Check the lower unit oil to see if it has water intrusion or metallic fragments as a chipped gear can lock up engine and transfer noise up driveshaft so it sound like lower bearing/cylinder problem. If the oil check out ok run a compression check on all cylinders, you should have 100psi or better and all cylinder shoul be within 10 psi of each other.

thank you very much, for taking the time to respond to my problem. I checked the compression, while the engine was cold. all three cylinders had 130 psi. after christmas i'll warm it up and do it over for a better reading. but does this only tell me if it a ring problem only. or will it tell me if it's a rod bearing problem. is their any way to know if it's a rod bearing without tearing the engine apart. also would a bad water pump make a pecking sound. the water pump is peeing a full stream. i don't have a water pressure gauge. thanks for reading this and have a very merry christmas.

The compression reading will tell us if any sudden damage has occurred to piston & rings, such as a loose bearing/metallic debris has went down side of piston. A bad water pump will not make a noise as it is rubber with brass hub, check the gear oil as in previous post. If not the gearcase the bottom bearing on crankshaft could be bad.

i went out and started my boat motor, using the water hose. i let it run for about 10 minutes, until the water stream was warm to the touch. while it was running, i pulled each plug wire off. one at a time. it never stopped pecking. i shut it off, pulled the kill switch. took the plugs out, and checked the compression, on each one. the readings were the same 127 psi on all three. and standing right beside the motor, while it was running, the picking sounded like it was in the middle of the motor. and as i gave it a little fuel, the picking speeded up.

Please check the gear oil in lower unit as a bad gear can cause noise to travel up driveshaft giving the impression of a engine problem. If oil is ok then you have a internal problem with engine.

the gear oil is clean, the knock is loud enough to hear. but not really loud. do you think a light knock, would get the rod out of round. where it bolts to the crank. the rings are still good, all three cylinders had 127 psi. so i was thinking of using new rod bearings, and new bolts. with the original rod and crank. do you think this will work. I've never done this before, but i think i can do it. i haven't tore the engine apart yet, I'm waiting on a repair manual.

Usually if you have a rod bearing fail the crank will usually be damaged from the rod bearing "hammering"(knock) on the journal surface. I would not order parts till you disassembled engine and found what has failed and been damaged, and you may get lucky and it be the lower bearing(cheap)that has failed.

I tore my engine down. on the 2006 mercury 90 hp 2 stroke that i have. the only way to see the top of the pistons, is to pull them out on the crank side of the block. the head side of the block is sealed up except for the spark plug holes. anyway the bottom piston skirt was scared up real bad. the other two looked like new. so i ordered, one piston, rings for all three pistons, a wrisk pin and bearings,rod bearings and bolts for all three pistons. a gasket kit, the piston failed due to lack of oil on the piston walls. this motor has about 80 hours on it and had to be tore apart. when i get it back together, i'm going to bypass the auto oiler. and mix the oil in the tank myself. i think it would still be running, if i had bypassed the auto oiler from the start. i know it will smoke more while ideling, but thats better than having to rebuild a engine with very low hours. ps any one out their that has a self oiling engine, you might want to think about. mixing your oil and gas your self. thats my 2 cents worth.

This is a common misconception that the "oiler" failed... If the "oil pump" had any problem it would not cause a single cylinder to fail, as mixture is sent to all the carbs,thus all cylinders would suffered lack of oil failure. Most likely you have a swollen inlet needle(from ethanol) or debris in high speed jet of lower carb.