slgr24

I was summerizing my boat today (2000 272 Boss w/ 502 Mag) and thought I may have heard a bit of engine knock when I ran it. In the summerization process I always change the engine and lower unit oil. I have done my own winterization/sumerization now since 98 with no problems in the past. When I pulled the boat out in the fall it was running fine with no knocks. I can hear it more in the exhaust than in the engine compartment. What might this be and how could of it happened over the winter. The boat was stored in a shop that never got below 45 deg. besides being winterized for colder temps.

jpclear

Are you running this on "earmuffs" out of the water with the unit trimmed way up or turned far left or right? If so this is just normal noise that you will hear from overtaxing the universals and gimble brg.when out of the water. If you trim down and straighten the drive and the noise goes away, put her in the water and enjoy your summer. Do hope it's just this simple. --- Jer

Crazyhorse

It could be a collapsed lifter.

slgr24

That could be it. I was running it with the earmuffs and the lower unit turned to one side and not near all the way down. Would this noise happen w/out engauging the drive? I never put it in gear out of the water. I'll keep my fingers crossed.

US1 Fountain

iTrader: (1)

Just another tid bit. Never let it run with the drive turned fully to one side. This will overheat and fry your ps pump and boil the fluid, not to mention the fire like smoke. Don't ask how I know!

If the drive was higher than the trim range (up into the trailer range) probably very well the u-joint as mentioned. Yes, the drive is always turning, wether in gear or not.

Griff

Also, you said you could hear the knock in the exhaust. Some exhaust tip flappers make a ton of noise at low rpm. Mine do and sound just like an engine knock. Put your hand on the exhaust hose near the transon where the tip connects and see if you can feel the knock.

DJW

I had a 98 272 and experienced the same noise. Mine also had Corsa quick and quiet II. The noise on mine was the exhaust internal flappers. It was nothing to worry about.

Lee

iTrader: (4)

Some of the better quality exhaust tips have flappers with a stainless counter weight that make some serious knocking noise at idle speed, You can use a yard stick and insert it into the exhaust tip to hold the flapper open to confirm this.

blue thunder

I have the tips with the counter weight flappers. They do sound like a bad knock when on the hose. Not enough water flow to keep them from banging. I would use a long screw driver or other suitable device as a listener. Press one end of it to your ear and the other end to different areas of the engine. When you hear the same noise through the listener that you hear without it you found the area generating the noise. If it is low on the block, it's a rod or main bearing.

If you have a rod/main bearing knocking, often the oil pressure will read low. How is yours?

BT

slgr24

Took it to the mechanic to be sure it was the flappers and sure enough it was. They sure do sound like a engine knock! Oh well worth the trip, ends up the thermostat was stuck open. Thanks for everyones input!!