Logo
FULL SITE MENU

OMC Cobra 4.3 making noises above 3700rpm.

M

Matt Rose

New member
As the title says i have a 4.3 cobra, its an 88 with the 2bbl rochester carb. has always run well for me up until recently when i started getting noise at high speeds when i trimmed up. took it to the mechanic, said it was the gimble bearing so i replaced it, now i can trim it, but after about 3700 rpm it will start making like a clicking type noise, its hard to describe, but i cannot attain full rpm even if i jam the throttle down. these kind if make me think its some sort of ignition problem since it will not rev up any higher than about 4000rpm. But the noise is so hard to tell whatit is at 40 mph......
 
Ayuh,... It's goin' Lean, 'n Detonatin',...

Check the contents of the fuel filter for water....

Fix it, or you'll burn up the motor, in No time...
 
The boat running hot ? Think a second what else is happening ? You asked what else. Check the plugs.

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

The oil dipstick is good no water in the oil ?

Here give this a read.

http://www.secondchancegarage.com/public/186.cfm

Compression test with all the plugs out on a warm engine with the throttle fully down.

All the cylinders are firing ? With the engine running to get warm for the compression test pull one spark wire off at a time and install back the wire move on to the next one, the engine should sound different, when you get to a wire and pull it the engine doesn't sound different the cylinder isn't firing.

We await your reply. You should after performing all the tests above have narrowed it down.
 
Matt Rose said:
making like a clicking type noise, its hard to describe,
Click to expand...
might be a good idea to take an experienced technician or even someone just familiar with boats and i/o drives for a ride. I'm sure most of us could tell you what that noise is in a few minutes of riding a long with the doghouse cover off, but words typed on a forum may just send you chasing your tail.
 
Back
Top