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WOT-What RPM for 4.3 GL?
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Author:  Nubby [ Thu Jun 26, 2008 7:34 pm ]
Post subject:  WOT-What RPM for 4.3 GL?
My manual says WOT is 4400-4600 for my 190HP 4.3L GL and I believe up to 4800 WOT for the EFI motor. I'm not positive if those are exact without looking up the numbers again. I called the FW dealer today about something else and he asked how the Solas prop he sold me two weeks ago was working out. I told him it was great (19P 14.5inch) for holeshot but I was hitting 5K RPM and had plenty of throttle left. He told me those motors can go 5,500 RPM and as long as it's not hitting the rev limiter I shouldn't worry about running WOT. The boat came from the factory with a 23P 14.25 prop and had the 19P when I bought it so that's what I put back on it. I don't need to run wide open and can still hit about 40MPH keeping it around 4,500 RPM but have PLENTY of throttle left. Does 5,500 RPM sound ok? It definately is more than the manual says but I figure the FW dealer should know what is "ok" to run at.
Author:  M3eater [ Thu Jun 26, 2008 7:50 pm ]
Post subject:  Re: WOT-What RPM for 4.3 GL?
Unless you need the extra punch of the lower pitched prop, due to a heavy load, etc., I would seriously consider adding more pitch. While that engine will turn 5500 RPM without blowing up .... you are giving it a real workout running above 4000 all the time. I would rather run lower RPM ..... as long as there is not a problem getting up on plane .... or pulling watersports.
Author:  robbo3 [ Thu Jun 26, 2008 9:34 pm ]
Post subject:  Re: WOT-What RPM for 4.3 GL?
If you've only had it a couple of weeks, see if they have a higher pitch that you can try out because you're uncomfortable with the high RPMs that it is running at.

I've never come close to hitting 5k. Usually we run around 3k.
Author:  Walt [ Thu Jun 26, 2008 10:20 pm ]
Post subject:  Re: WOT-What RPM for 4.3 GL?
A marine engine is a Truck engine. They are designed to tow.. that is low RPM torque, and none of this high RPM crap. Above 5k rpm you will start floating your valves, and reducing the life of your valve train, plain and simple. Your best performance should be in the 3500-4500 rpm range, with good torque below that. On my last boat (with a merc 4.3) I avoided prolonged running above 3500 rpm. Think about your car.... how hard do you push that????
Author:  Aussie_Horizon_190 [ Fri Jun 27, 2008 12:07 am ]
Post subject:  Re: WOT-What RPM for 4.3 GL?
I find with mine around 4500rpm is max. With the original 23 pitch prop it is doing right on 50mph (by GPS) at those revs. 19 pitch prop will get you out of the hole quicker, but you lose top end and it will make the engine rev harder as you have found (and me!).

IMHO sustained revs at 5500rpm with this engine (cast crank, cast pistons, balance shaft etc.) is flirting with disaster... Also, I don't believe there is a rev limiter on the 4.3GL, it simply stops revving any harder when the valves begin to float or it runs out of air... :shock: Probably OK to rev it that hard for a few seconds, but not continually.
Author:  Nubby [ Fri Aug 15, 2008 9:59 pm ]
Post subject:  Re: WOT-What RPM for 4.3 GL?
So do you still use the factory 23P prop? I know I'd be where I'm supposed to if I went back to the 23P it's supposed to have but question how the holeshot would be for wakeboarding. If you're not using a 23P what do you have? If you ARE using a 23P, how's the holeshot...can you live with it? I'd like to run about 50 once in a while but am fine with 40 and good holeshot right now. Just curious what my options are. Dealer told me now to mess with a 21P because "you may as well go with a 19P then." but now I'm wondering if a 21P would be a good medium.

Aussie_Horizon_190 wrote:
I find with mine around 4500rpm is max. With the original 23 pitch prop it is doing right on 50mph (by GPS) at those revs. 19 pitch prop will get you out of the hole quicker, but you lose top end and it will make the engine rev harder as you have found (and me!).

IMHO sustained revs at 5500rpm with this engine (cast crank, cast pistons, balance shaft etc.) is flirting with disaster... Also, I don't believe there is a rev limiter on the 4.3GL, it simply stops revving any harder when the valves begin to float or it runs out of air... :shock: Probably OK to rev it that hard for a few seconds, but not continually.
Author:  Walt [ Sat Aug 16, 2008 8:01 am ]
Post subject:  Re: WOT-What RPM for 4.3 GL?
Have you tried this link yet? It's all over in these forums.....

http://www.go-fast.com/Prop_Slip_Calculator.htm

Hope that helps!
Author:  LouC [ Sat Aug 16, 2008 9:57 am ]
Post subject:  Re: WOT-What RPM for 4.3 GL?
I don't think I'd want to push that motor over what the manufacturer said it can do, keep in mind that these are old school low tech engines that were not intended to run at high revs continually like a double over head cam engine. I'd make sure that it can hit the manufacturer's max rpm range at WOT, too low on the rpm and the engine is laboring, too high and you risk over-revving unless you watch the tach carefully. As an example, my 88 FW with the 4.3 4-bbl carb came with a 14.5x19 pitch prop. It only pulled 4200 rpm at WOT which is too low (OMC said 4400-4800). I changed to a 15x17 pitch and it now gets 4650 at WOT which is right were it should be. It jumps up on plane much quicker and does not strain to accelerate. I still cruise at 3500 or so because that is a comfortable RPM for them to run at continuously.
Author:  Aussie_Horizon_190 [ Sun Aug 17, 2008 6:35 pm ]
Post subject:  Re: WOT-What RPM for 4.3 GL?
I am running the stock aluminum Volvo prop FW shipped the boat with and IMHO it is a real good combination (I imagine that FW would have spent some time sorting this package out during the design stage). Absolutely no problem at all pulling wakeboards up even with 5 adults on board, and at 4500rpm it is doing right on 50mph by my GPS (2 adults, full tank of fuel).

If in doubt, buy the genuine 14.25" x 23" Volvo prop that shipped with the boat (Volvo P/N 3817470) - I paid around $140 for my replacement at:

http://www.getaprop.com/content-product_info/product_id-6762/volvo_penta_sx_propeller.html
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