RPM SURGE
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Elder User
Joined: Jul 2010
Posts: 610
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From: Sequim. WA
RPM SURGE
I have twin 7.3 IDI engines in my boat. Each engine has about 3500 hours on it. I normally run at 2600 rpm but also idle a lot for trolling.
The boat sits inactive for the winter in cold weather. I usually only operate it in the summer.
This last season I had a new problem. When bringing the boat up on step I set the throttles at 2000 rpm to start with then move them up to 2400 to 2600 rpm for cruise.
The problem is that the port engine will surge to 2200-2400 rpm after I set it to 2000 rpm. If I bring it back to 2000 rpm it will stay there and I can advance it up to cruise rpm when I am ready.
It does this every time I took it out last season.
At first I thought that it might be a transmission slipping but these are new gear boxs (ZF 250 units, rated at up to 450 hp) with less than 300 hours on them.
I suspect that it is the injection unit/gov and have planned to remove it and send it to a shop for testing and repair as necessary.
I am wondering if any one out there has any other ideas on this problem before I go through the work of removing the injection unit/
Thanks.
The boat sits inactive for the winter in cold weather. I usually only operate it in the summer.
This last season I had a new problem. When bringing the boat up on step I set the throttles at 2000 rpm to start with then move them up to 2400 to 2600 rpm for cruise.
The problem is that the port engine will surge to 2200-2400 rpm after I set it to 2000 rpm. If I bring it back to 2000 rpm it will stay there and I can advance it up to cruise rpm when I am ready.
It does this every time I took it out last season.
At first I thought that it might be a transmission slipping but these are new gear boxs (ZF 250 units, rated at up to 450 hp) with less than 300 hours on them.
I suspect that it is the injection unit/gov and have planned to remove it and send it to a shop for testing and repair as necessary.
I am wondering if any one out there has any other ideas on this problem before I go through the work of removing the injection unit/
Thanks.
Posting Guru
Joined: Dec 2012
Posts: 1,065
Likes: 2
From: western washington
is your throttle oil or cable? if it is cable you may have to re rout the cable on the affected engine, may have a spring affect when advancing the throttle, when you advance the throttle the engine vibration may make the cable move a tiny bit more after you stop advancing the cable, cable Creep.. the rpms you are pulling are low in the engine's power curve, and the throttle can be very sensitive right when the engines, start getting the fuel they want.
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