200 EFI knock

[Double 0]

I took my boat with 1998 200hp EFI Merc. & less than 100 hrs. in to the dealer after being stored for the winter to have him change the water impeller, filters, plugs etc. When I put it away last fall I had fogged the cylinders and left fuel in the lines. Everything was running good and quiet last summer. I had it running for half a minute at home (with water connected to intakes) before I took it to the dealer. It sounded fine at that time, however the cowl was on.<br />After he did the work the dealer called and had me go look at the motor . With the cowl off it was making a fairly loud knocking sound coming from the powerhead. He said that he had checked the driveshaft and it was connected OK. He suggested that maybe a rod was loose or bad bearing on the crank. The dealer suggests installing a new long block as it may be the most economical way to repair the problem vs. teardown and rebuild but he doesn't know what the cause could be. Without tearing it down, any ideas what may be wrong? Could a bearing or connecting rod be the problem? Could a defective spark plug or ignition problem cause the knock?

 

[profish00]

Re: 200 EFI knock

check the spark plugs,decard the engin

 

[vinney]

Re: 200 EFI knock

A lower unit can make sounds of a knock (broken pinion gear). If you have ruled out the lower unit. Its the power head. Most common knock is conn. rod to crank. You can pull the heads and deterimine which hole is the cause of the noise. To rebuild or not is based on whether the crank is junk. Its a great engine to rebuild.

 

[TampaTom]

Re: 200 EFI knock

I had a knock sound that seemed to come from the powerhead but actually sound was coming up from the lower unit (which oil had leaked out of.) The sound I had was intermitent which was a tip it wasn't from the powerhead which would probably produce the sound every revelotion.

 

[Double 0]

Re: 200 EFI knock

Originally posted by vinney:<br /> A lower unit can make sounds of a knock (broken pinion gear). If you have ruled out the lower unit. Its the power head. Most common knock is conn. rod to crank. You can pull the heads and deterimine which hole is the cause of the noise. To rebuild or not is based on whether the crank is junk. Its a great engine to rebuild.

 

[Double 0]

Re: 200 EFI knock

I took the boat home and checked the plugs and they were OK. Then I took the boat to another repair shop to have it checked out. That mechanic listened to the motor and said that he bet anything that a rod was loose. I left it with him and he called me back the next day and said that the flywheel was loose and that was causing the knock. The says that he has never seen that happen before on a 200 Merc. engine. So I am very happy that the fix is easier and much less expensive than expected and I can get back on the water soon. I guess that it pays sometimes to get a second opinion.

 

[vinney]

Re: 200 EFI knock

You found a good guy. We have seen that a few times. It will usally take the flywheel out or the crankshaft splines. The problem was the factory didn't torque the flywheel nut to spec. I would check the nut/flywheel at the end of your boating season. I would make sure they install a new flywheel nut and maybe some locktight 271 on the splines.