volvo 5.7 tbi RPM

[duststang]

Anyone know the redline RPM for a 99 Volvo 5.7 TBI? My boat shows 5000RPM as ideal WOT but nothing about redline RPM of the motor. Currently I have a duo prop and the motor will go to 5600RPM WOT. The gauge might be wrong but just trying to understand what RPM I should not exceed?
thanks,

 

[Don S]

Re: volvo 5.7 tbi RPM

The first thing to do is check the tach. 5000 is max WOT rpm for the TBI engines. 5600 is way too fast.
You say currently on your Duo Prop, was it replaced? Is it the right gear ratio?

 

[QC]

Re: volvo 5.7 tbi RPM

There are no published "redlines" on Marine engines. Since the max RPM is controlled by propeller load it is not necessary. No way to exceed it except in neutral

 

[Tail_Gunner]

Re: volvo 5.7 tbi RPM

As above your tach is off the ecm has a rev limiter built into it and cuts off fuel for a nano second. It will allow the engine to trun to 4900 and some change but takes over from there. When you are running at WOT do you ever hear a very slight miss..its very slight but if you do stay away from wot you are burning lean and that's very bad and more than probably need a larger prop. Duo's are very expensive it might not be worth dropping one pitch just keep your hand out of the throttle..As Don said post your gearing and your true rpm when you get your tach sorted out...along with the prop size...

 

[duststang]

Re: volvo 5.7 tbi RPM

ok so if it was over 5000 RPM the computer will cut it down and I should notice the engine would start missing? My tach must be way off because 5600 RPM is way over 5000 RPM. I have not noticed any changes in performance when it goes above 5000 RPM. How do I tell the drive ratio? I bought the boat used so not sure if the prop was ever replaced. Is it possible to only replace one of the props or do I have to replace both?

 

[Don S]

Re: volvo 5.7 tbi RPM

Here is a copy&paste from the service manual on the operation of the rev-limiter.

RPM Limiter
The RPM limiter is not a switch or sensor, but rather a
function of ECM circuitry. The ECM monitors engine
speed on the distributor’s IC “REF HI” line. If RPM exceeds
the upper end of the engine’s RPM range by 200
RPM or more, all injector operation immediately stops.
Injector operation returns to normal at the moment RPM
drops back into the operating range.

For your drive gear ratio, you can look for a tag on the upper gear box, just in front of the top cap.
You can also remove the props, and the anode and the ratio should be stamped in the carrier.

 

[duststang]

Re: volvo 5.7 tbi RPM

thanks I will look.
actually had the boat out this weekend and now it is bogging at WOT but runs good 3/4 throttle 4200RPM's.

 

[Bondo]

Re: volvo 5.7 tbi RPM

thanks I will look.
actually had the boat out this weekend and now it is bogging at WOT but runs good 3/4 throttle 4200RPM's.

Ayuh,... Check the fuel filter for Water, 'n replace it....

 

[duststang]

Re: volvo 5.7 tbi RPM

So the RPM gauge is off. Actually I tap on it and it moves around so I guess it is not actually over revving. the drive is a 1.95.
replaced dist cap, rotor, fuel filter, air breather, and plugs. Put Seafoam in gas then took it out yesterday and it still bogs WOT. I noticed all the plugs had a lot of gas and #3 was more black than the rest. The back of the boat still had black on it like it is running rich.