hitting rev limiter at 3/4 throttle.

[fixnfly]

I believe this is a prop issue. I'm hitting the rev limiter at 4400 rpm and only at 3/4 throttle. Factory manual says WOT range is 4400-4800. I primarily cruise and pull a knee board. Looking the change to a SS prop anyways.


2004 Monterey montura 190ls
4.3l GXI-D 225hp
SX-M1 1.79 ratio
stock aluminum 3 blade prop 14.5x19

dry weight of boat 3200 lbs + 220 lbs fuel + 800 lbs people = 4220 lbs
average top speed 35-38 mph

Looking for a better whole shot and a few more mph, nothing crazy. I just hate being at 3/4 throttle and hitting the rev limiter.

I would appreciate some opinions before I purchase a new SS prop.

 

[Don S]

Re: hitting rev limiter at 3/4 throttle.

I moved this to the Volvo forum, a prop is not going to make your rev limiter lower.

You need to check your engine temp first. Does it show 160? or below? It shouldn't.
If it's showing normal temps (160+) on the gauge, you will need to get the engine hooked up to a diagnostic tool and check the ECT sensor (Engine Coolant Temp) to find out what it's showing.
The ECM on your engine has a cold rpm rev limit that reduces the rpm if the ECT shows too cold.
As an example, at 68? the limit would be 4000 rpm, at 104? the rpm would be 4600.

Note: The ECT and the gauge sender are not the same unit.

 

[fixnfly]

Re: hitting rev limiter at 3/4 throttle.

I was unaware of that. I recently removed the thermostat cause it was stuck closed. Water temp around here is about 65 degrees. The engine is running cooler around 120-125. That would also explain the rev limiter hitting at 4200 earlier in the morning with cooler water temps.

Why does the ECM have a cold rpm rev limit in cooler engine temperatures?

Thank you!

 

[aerobat]

Re: hitting rev limiter at 3/4 throttle.

Why does the ECM have a cold rpm rev limit in cooler engine temperatures?
Thank you!

to prevent excessive wear and damage when you force the cold engine to very high rev,s .

 

[Don S]

Re: hitting rev limiter at 3/4 throttle.

Why does the ECM have a cold rpm rev limit in cooler engine temperatures?

Because Volvo wanted it that way. It protects the engine from the higher rpm and low temps and probably a bit about the fuel mapping.

If you had an old carbed engine, it wouldn't be a big deal (other than being hard on the engine).
Put in a new thermostat and fix it right.

Do you half azz systems on aircraft?

 

[fixnfly]

Re: hitting rev limiter at 3/4 throttle.

HaHa, never, but when I overheated it got me home last week. With the warm weather fast approaching its hard to stay off the water. I bought the boat late last year and have been wanting to take it out all winter.

Thanks for the help.

 

[Don S]

Re: hitting rev limiter at 3/4 throttle.

Once you get the thermostat fixed and the overheat cured, then run it and see if you still want another prop once the engine works.