WTF is that loud wisssssss sound (motor)help
#1
Registered
Thread Starter
Join Date: Aug 2009
Posts: 460
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
twin built up 302 motors in my older boat. Edelbrock Alum heads, Scorpion roller rockers Edlebrock performer intake, speed Demon 650's MSD dist, ign box, blaster coils, Comp chain and gears and Comp Cam. Max timming at 36.
Kodiak Alum exhaust and risers.
At max throttles I get a loud hissing sound that comes in at about 4400- to 4800 rpms port motor only. Sounds like a turbo blowing off. Still runs good but loud... then when you pull back throttles this one seems to back off harder. Any ideas?
I swapped carbs that didn't do it.
No hissing from idle up through the rpms so can't tell if there is a vac leak.
Kodiak Alum exhaust and risers.
At max throttles I get a loud hissing sound that comes in at about 4400- to 4800 rpms port motor only. Sounds like a turbo blowing off. Still runs good but loud... then when you pull back throttles this one seems to back off harder. Any ideas?
I swapped carbs that didn't do it.
No hissing from idle up through the rpms so can't tell if there is a vac leak.
#4
VIP Member
![](https://www.offshoreonly.com/forums/images/icons/prop.gif)
Join Date: Nov 2008
Location: Bend Oregon
Posts: 503
Likes: 0
Received 0 Likes
on
0 Posts
#5
Registered
Thread Starter
Join Date: Aug 2009
Posts: 460
Likes: 0
Received 0 Likes
on
0 Posts
#6
Registered
Thread Starter
Join Date: Aug 2009
Posts: 460
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
I checked to see if the secondaries would open freely by opening the throttle and moving the linkage. Seems to move real easy.. Now the motor wasn't started.... I guess I'll check that next with motor running. Just hard to do on the water with hatch open etc..
I just don't know what else can cause such a loud shhhhhhhh sound at open throttle... And not open throttle from a dead stop.. Only at the highest RPM...
I have all my timing coming in at 1500.. Maybe 36deg is too much. But plugs look good and no pinging..
I just don't know what else can cause such a loud shhhhhhhh sound at open throttle... And not open throttle from a dead stop.. Only at the highest RPM...
I have all my timing coming in at 1500.. Maybe 36deg is too much. But plugs look good and no pinging..
![Hitit](/forums/images/smilies/more/hitit.gif)