Mercruiser 165 noise

M

mabshire

Cadet
Joined
Dec 8, 2004
Messages
9
I have a 1978 165hp 4.1 l mercruiser. <br />Head redone.<br />Block redone and bored.<br />New Pistons, New Bearings, New Camshaft, New Lifters etc.<br />Crankshaft turned.<br /><br />Here is the problem. The motor makes a loud ticking or tapping noise comming from around the distributor oil filter area. When I tighten down the Exhaust or Intake rocker arm in cylinder #1 (so that the valve stayes open) the noise stops, but i have no power from that cylinder and the engine runs rough. It only does that for that cylinder.<br /><br />Can anyone please help
 
Dunaruna

Dunaruna

Admiral
Joined
May 2, 2003
Messages
6,027
Re: Mercruiser 165 noise

mabshire, welcome to i-boats!<br /><br />I can remember an exact same thread a while ago, rather than go through all the likely causes again and the eventual fix I'll try and find the thread for you.<br /><br />Aldo
 
B

bigbrownbuku

Master Chief Petty Officer
Joined
Sep 17, 2004
Messages
885
Re: Mercruiser 165 noise

lifter could be nfg mab. also pull the pushrod and check the lube gallery is free and open. check the underside of the rocker for deformities around the pushrod contact area.
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Mercruiser 165 noise

Did you check the fit of the bearings (Main and rod) to the crankshaft with Plastigage. If one of the rod journels was machined wrong and there was too much gap between the crank and the bearing, it would "Tap". But when you relieved the compression by over tightening the valves you may not get the noise.
 
M

mabshire

Cadet
Joined
Dec 8, 2004
Messages
9
Re: Mercruiser 165 noise

I have new pushrods lifters rockerarms etc.... whole new valve train....<br /><br /> This is what happened the first time i took the boat out it made this noise after about 5 or 10 <br />minutes of running... <br /><br />I think i will check the bearings...
 
M

mabshire

Cadet
Joined
Dec 8, 2004
Messages
9
Re: Mercruiser 165 noise

Well, I think i found the problem....<br />I went ahead and pulled the piston in cylinder #1<br />and It did not look too good. On the left side of the piston was eaten up, some of the piston was melted on the cylinder wall, but on the bright side most of the damage was on the piston and I was able to remove the aluminum on the cylinder wall. The deposits of aluminum on the cylinder wall was when the piston was at its lowest point on the stroke and all on the left side, the right side of the piston looked new with almost no ware what so ever. The engine might of had about 150 hours on it.<br /><br />I honed the cylinder and it looks good.<br /><br />What might have caused this problem?<br /><br />Thanxs
 
tommays

tommays

Admiral
Joined
Jul 4, 2004
Messages
6,768
Re: Mercruiser 165 noise

mab<br /><br />it could be a few things<br /><br /> a perfect motor will have a meltdown if the prop is to big theres so much engine cover its hard to here it ping like a car<br /><br />the timeing can have to much total advance and do the same thing<br /><br />or the motor can be to lean and also melt<br /><br />i have had a lean condition before but it showed up on the temp guage before any damage was done and i was just luckey if it had run a littel longer i would have had a meltdown<br /><br />tommays
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Mercruiser 165 noise

Since the engine was bored and new pistons installed, are you sure there was enough clearance for the piston. If it was too tight, it will seize like that.<br />Another problem is if the bore job was done off center the cylinder wall could be too thin and it will flex and also cause a seizure.<br />Once they start seizing and galling heat will build rapidly and cause some melted spots
 
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