merc 1972 165 barely runs after 1/2 hour

m keen

Recruit
Joined
Jun 16, 2012
Messages
5
Hi guys, newbie here. have had a problem for the last couple of seasons with the engine slowly cutting back to a very rough idle after a hard run ( 1/2 hr to an hour @ 3000 rpm). have to limp back to port and sounds like th engine will barely stay running on slow rpm, very rough. could this be a distributor problem? on shorter runs there is not a problem and boat runs well. any suggestions would be appreciated.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,464
Re: merc 1972 165 barely runs after 1/2 hour

Hi guys, newbie here. have had a problem for the last couple of seasons with the engine slowly cutting back to a very rough idle after a hard run ( 1/2 hr to an hour @ 3000 rpm). have to limp back to port and sounds like th engine will barely stay running on slow rpm, very rough. could this be a distributor problem? on shorter runs there is not a problem and boat runs well. any suggestions would be appreciated.

Ayuh,... Welcome Aboard,... Is this 165hp, a 4 cylinder, or 6 cylinder,..??
 

a1nowell

Chief Petty Officer
Joined
May 12, 2009
Messages
437
Re: merc 1972 165 barely runs after 1/2 hour

m keen,
This is what happened with my 470:

In early April I was out for the first time this spring and after about 20-25 minutes of running just fine, my 470 started to run like crap. Nursed it back to the dock checked everything over, all good (new plugs & wires the previous week, Petronics ignition). The engine cooled down, fired right up and I went out again, in 20-25 minutes it started to miss something terrible. A friend suggested the coil, I went to NAPA and got a $14.00 universal 12v coil and installed it. Problem solved. I have probably been out 6-8 times since then, runs like a top.

Just my $0.02 worth,

Larry
 

cr2k

Captain
Joined
Mar 19, 2009
Messages
3,730
Re: merc 1972 165 barely runs after 1/2 hour

If the engine is not overheating, I agree it could be the coil. This is bad coil behavior. Changed fuel filter? Fuel pump problems?
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,464
Re: merc 1972 165 barely runs after 1/2 hour

fuel system seems to b good and new filter

Ayuh,.... "Seems" ain't quite tested, 'n confirmed....

There ain't no Easy Button,... You gotta fix it, it won't do it by itself...
 

m keen

Recruit
Joined
Jun 16, 2012
Messages
5
Re: merc 1972 165 barely runs after 1/2 hour

yep. yr right. will grab a new coil as well just to b sure. thanks guys. will run it next weekend and let u know
 
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