5.7L Engine Problems

[Chris611]

Today on the river I was running my boat with a 5.7L Mercruiser at WOT (4600). It got to 4600 and the RPMs stayed there for about 60 seconds then the RPMs began to drop and I could hear a ticking noise from the right side valve cover area. I slowed and stopped. The noise continued. I shut off the boat and let it sit a minute or so and then started it and the noise was gone. Again hit WOT and same thing happened. And shut it down and went away. I cruised the rest of the way at about 4000 RPM and had no problems. Any thoughts on what this may be? The noise is a tapping noise, sounds like a loose rocker or exhaust leak. The engine has otherwise been running well. I do have oil pressure and there is the proper amount of oil in the engine.<br /><br /><br />Thanks<br />Chris

 

[Don S]

Re: 5.7L Engine Problems

Recheck your oil, if it's too full you could have the crankshaft hitting the oil and causing it to aireate (sp) which will cause the lifters to get a little noisy.

 

[Chris611]

Re: 5.7L Engine Problems

Thanks Don. It just happened that Friday night I had check the oil on the dipstick and it was above the full mark. I didn't think anything of it. I always worry about being too low, but sounds like too full is bad also. When the engine was making the tapping noise I noticed slight fluctuations in the oil pressure gauge, but it still had pressure. I supppose this was the foamy oil. What is the oil capacity for a 5.7L merc?<br /><br />Thanks<br />Chris

 

[Chris611]

Re: 5.7L Engine Problems

I also talked with the boat mech. and he suggested "Sea Foam" that may help clean out the hydraulic lifters. Has anyone used that? I asked about there being too much oil and hitting the crank and he seemed that it would be unlikey. Says the oil pan is baffled pretty well and unless the waters were very rough, didn't suspect that. I am going to recheck the oil at home though. How long do you guys run your engines at WOT? <br /><br />Thanks<br />Chris

 

[Hog Wild]

Re: 5.7L Engine Problems

Just FYI, my lifters/cam went bad at 1760 engine hours and when they started going bad they did exactly as you are describing (sorry to mention). I chased my tail around with Sea Foam, adjustments like oil, timing, compression, etc. But it just got worse and worse no matter what I tried. Wish I knew more about your motor's current life status before I comment much. The oil would have to be grossly over filled to cause what you're mentioning. WOT certainly has a lot to do with engine life. I have to admit I'm so excited to have a new engine now and everything in great shape, yeah, it cost me a few thousand but how nice now. I run lots of WOT and I'm sure my engine will not last long. but should go another 2000 hours. I had an 1986 5.7L that I got used. I put on 300 hours a year which added up in 4 years over the previous owners 80 hours a year ave. I put a whole new vortec power plant in over a rebuild to get all new parts (old alpha drive still). So nice. Haven't technically fully disassembled the old engine yet. After about 50 hours from what you are posting now I found metal "sand" under the valve covers. Thats how I'm thinking lifters/cam. My oil filter never would get any metal trapped in it that I found (I cut it open). but once the knock got bad enough and I started loosing power I replaced it. Mostly my advice is try some cheap/easy things, run it long as you can and just keep tabs on it's progress. You maybe able to run a couple years like this but I think you'll see it slowly get worse.