HELP!! 7.4L/330HP with Issues!
#1
Registered
Thread Starter
Join Date: Mar 2002
Location: Lake Winni, NH
Posts: 81
Likes: 0
Received 0 Likes
on
0 Posts
![Unhappy](/forums/images/icons/icon9.gif)
HELP!! A friend of mine just sent this to me. Its a 7.4L 330 Fuel Injected motor.
When I run the boat at full speed (4200 RPM's) it could take anywhere between 15 and 45 minutes before the engine cuts out. I can watch the tach go from 4200 rpm's to 0 and then spike back up to 4200. It will keep doing this sporadically. If it is not doing that, while at full throttle I can watch the tach drop from 4200 rpm's to 3800 and remains there. If I keep running it, it will drop to 3200 RPM and stay there. During both of these occurrences the boat will no longer idle it will stall. If I let the boat sit for 15 minutes or so the problem goes away and I have to wait another 15 minutes or so to see it happen again. I can run the boat at 3200 RPM's and never see the problem. The marina has run a fuel pressure check and that was OK , replaced the coil and replaced the computer I think he called it the ECM. The error codes the computer originally gave him was a knock sensor and the ECM. Any Ideas???????
When I run the boat at full speed (4200 RPM's) it could take anywhere between 15 and 45 minutes before the engine cuts out. I can watch the tach go from 4200 rpm's to 0 and then spike back up to 4200. It will keep doing this sporadically. If it is not doing that, while at full throttle I can watch the tach drop from 4200 rpm's to 3800 and remains there. If I keep running it, it will drop to 3200 RPM and stay there. During both of these occurrences the boat will no longer idle it will stall. If I let the boat sit for 15 minutes or so the problem goes away and I have to wait another 15 minutes or so to see it happen again. I can run the boat at 3200 RPM's and never see the problem. The marina has run a fuel pressure check and that was OK , replaced the coil and replaced the computer I think he called it the ECM. The error codes the computer originally gave him was a knock sensor and the ECM. Any Ideas???????
#2
Registered
Join Date: Oct 2002
Location: Cincinnati, Ohio
Posts: 1,477
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
As a test diconnect the tach, I have heard of two boats with the identical problem you described and it ended up being the tack causing problems with the ignition system. It might be worth a try. The fact that it runs fine after it cools sounds like a ignition module problem.
#3
I hate the winter!!
![](https://www.offshoreonly.com/forums/images/icons/platinum_member_star.gif)
Join Date: Jul 2001
Location: long island, new york
Posts: 2,707
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
When the motor died on you, did you check for spark and fuel? You have to determine which is droppping out on you before you change parts.