4.3 RPM Question

Rick on another thread you mentioned the following?

?.A WOT RPM that's too low can damage the engine.?

I have a 4.3 and very seldom run at WOT. I grit my teeth when I look at the RPMs above 4000. I would never run a car engine at this speed except for passing/
Are these standard blocks from GM or are they designed to run at much higher RPMs than the car engines?

Everyone's thoughts are welcome.

Thanks for another Ricky

Re: 4.3 RPM Question

They are designed to run at high revs for long periods of time...

The way you set the engine up is to run it at full throttle (with normal load and trim) and see what RPM it is making. It should be making 4400-4800rpm. If it's making less, then you are overloading the engine (not just at full throttle, but the complete rev range) and need to get a smaller prop (in inches of pitch)... Or you will end up detonating pistons...

I have my engine propped so I am actually over the top end if I run wide open. Fortunately (or unfortunately) the weather here rarely allows such high speed. That said, when the weather does suit, I am 'balls to the wall'. If I push it all the way with the 17" prop, I hit the rev limiter at 5100, I just back it off to 5000.... Happy camper!!!! 39.5 knots!

If I know the weather will lend itself to that sort of abuse, I throw my 19" prop on, and get her purring along at 43.2 knots, pulling 4600 rpm.... I'm happy to do that all day, just the fuel bill at the end of the day (and my spine) that hurts....

Chris.....

One more thing... Stop gritting the teeth above 4000, smile man.. That's when the fun starts....

Re: 4.3 RPM Question

The "too low WOT rpm" term usually means that the engine cannot get into the proper top rpm range, not that it is harmful to run it at lower than redline. You need to see what RPM's the engine can attain at WOT to make sure it is propped correctly. If the engine cannot reach top RPM's then it could be overpropped and that is hard on an engine.

Re: 4.3 RPM Question

Thanks for explanation. When I get her good and broke in I will open her up to see what happens. What is the rev limiter suppose to be set at on a 4.3?

Re: 4.3 RPM Question

Lots of different configurations thru the years for that engine. I have no idea, but if you post the serial number of your engine then someone may look it up and respond.

Re: 4.3 RPM Question

Depends on your ignition setup, you may not have a rev limiter. The prop is what prevents the engine from going to fast. Merc gives a range of what your WOT rpm should be in. To low, you are lugging the engine (NOT Good) to high an rpm and you are just over reving and not using the full potential of your engine.

Re: 4.3 RPM Question

Found these specs in "Ether" world.
Mercury MerCruiser 4.3 TKS (190-hp) (Inboard) Specifications


Fuel Type
Gasoline

Horsepower
190-hp

Warranty
3 Years

Displacement (cu/cc)
262.00 cu / 4,293.41 cc

Number of Cylinders
6 Cylinders

Configuration
V6

Cooling System
Raw Water

Weight (lbs/kg)
848.00 lbs / 384.65 kg

Charging System
65 A

Length/width/height
28 in / 30 in / 21 in

Full Throttle RPM
4800

Thanks everyone for your help!

Ricky

Re: 4.3 RPM Question

Do you have the serial number off your engine, have no clue what this "Ether" world is.