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Volvo Penta 50GL knock

M

mitchmagee

New member
"I have a 2006 VP 5.0 GL-F w/

"I have a 2006 VP 5.0 GL-F w/ SX-M sterndrive now with 115 fun filled hours. About a month ago, it started to infrequently have a "hard knock" on acceleration when pulling a skier out of the water. The first time I heard it, I thought the ski rope had broken. It does not happen but maybe every 10th time on acceleration and it does not sound like the "traditional" knocking that I am familiar with on car as it goes up a hill. When it occurs, there is one, two or sometimes 3 hard hits (once a thought I had lost power for a second). I took boat to Marina first thing in morning this week and of course could not recreate sound. It seems to appear more often after I had been running for a while. I have just run through a tank of premium, changed the oil (marina was grasping for straws and offered speculation that "lifter valves cavitating/not getting oil"???), I have acclerated much slower (to chagrin of some of my skiers). (I also cleaned out the stern storage to make sure no objects were slidding or hitting anything). I have used my Marina to do annual checkups (oil changes) and storage. Boat is on a lift out of water when not in use.

Sporadic knocks continued this weekend. I would appreciate any ideas on what else to look for or "data to collect" to help problem solve. Thanks"
 
"Mitch,

Some thoughts to co

"Mitch,

Some thoughts to consider. I have a volvo penta 4.3 GL that appears to "knock" some times. However I have found it to be some water in the fuel water seperator. On hard acceleration the fuel and water are both pumped into the carb. On slow acceleration it does not. The "knock" I hear is really a pop when the water hits the cylinder. Check and see if you have water in the separator, put in a clean (dry) glass jar and look for water on the bottom. Also if you have not yet checked your cap/rotor, I have found that mine will misfire at hard throttle (high rpms) due to corrosion on the cap pickups. Both are an easy fix. Good luck and hope some of this helps."
 
Mark-
Thanks for feedback. W

Mark-
Thanks for feedback. We have not had a chance to get back on the water (kids off to college etc.) but will post results on separator investigation as soon as I get a chance to check it out.
 
"We took the boat out of the w

"We took the boat out of the water in late October and winterized it couple weeks ago. I could not find any evidence of water in fuel filter/ seperator. Also did not experence problem through the Fall (although we did not run it nearly as much or as hard as when we were on a week long vacation in August). I did fill the gas tank this winter (I left it half empty last year). If I come across any other data/info observations, I will post. Again, thanks"
 
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