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| RPM's https://www.smwebhead.com/phpBB3/viewtopic.php?f=3&t=9196 |
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| Author: | Dmoe103 [ Sun May 06, 2012 8:02 am ] |
| Post subject: | RPM's |
I have a Four Winns H200 w/ volvo Penta 4.3 SXi. What should be my max RPM's at full throttle. I ran it yesterday and was at 3400 rpm and 45 mph full throttle. 3 adults in the boat. I am trying to make sure that my throttle is setup properly and that I am getting max power. |
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| Author: | LouC [ Sun May 06, 2012 9:23 am ] |
| Post subject: | Re: RPM's |
That's about 1000 rpm too low, you have to find out why. Could be a fuel system problem, or the wrong prop. Most V-6/V-8s run 4200-4800 full throttle. If you don't reach that level, then you run the risk of straining the engine and overheating the valves. They are designed to hit a specified rpm at wide open throttle. When I got mine it had the wrong prop on it. It had a 14.5 diameter by 19" pitch and it needed a 15" diameter by 17" pitch, that put it right where it should be. |
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| Author: | Dmoe103 [ Mon May 07, 2012 6:08 am ] |
| Post subject: | Re: RPM's |
What is the best way to determine the proper prop for my boat? |
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| Author: | LouC [ Mon May 07, 2012 7:02 am ] |
| Post subject: | Re: RPM's |
I would look in the Volvo Penta owners manual for your boat as a starting point. What prop does it have on it now? The usual procedure is to make sure the engine is in a proper state of tune, that there are no fuel system problems (fuel filter not clogged, fuel vent not clogged, anti-siphon valve not sticking) and make sure the ignition system is functioning properly (late models with electronic ignition, you can check and replace the plugs if needed). Then do some test runs. For each 1" drop in pitch, you will pick up 200 rpm. Yours is way off, either something is wrong with the fuel system, or someone put the wrong prop on it. Post up what year engine you have and what prop you have and then people with the same boat/engine can tell you what prop they are using. The only other thing that can cause this problem, and it can happen, is if the outdrive was ever replaced, and they put one on that had the V-8 gear ratio instead of the V-6 gear ratio. Because the V-8 has more power it can pull a higher gear ratio (lower numerically) and that would put the V-6 rpms too low. |
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| Author: | ric [ Mon May 07, 2012 8:41 am ] |
| Post subject: | Re: RPM's |
It's on the four winns spec page what prop it came with |
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| Author: | Dmoe103 [ Tue May 08, 2012 7:56 am ] |
| Post subject: | Re: RPM's |
The boat is a 2008 H200 with 90 hours on it. I bought it new. It came with a 14.5 x 21 3 blade alum prop. I put a 14.5 x 19 3 bladealum on it hoping for more hole shot. I am going to put the original 21 prop back on and see what the rpm's are. |
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| Author: | RotaryRacer [ Tue May 08, 2012 8:03 am ] |
| Post subject: | Re: RPM's |
21" pitch will lower the RPMs more. We have to make some assumptions. You are trimming the drive once on plane to get the maximum RPMs and speed correct? You don't have an unusually heavy load correct? Since you bought the boat new, it would seem that you have put all 90 hours on it. Has it always performed this way? Has there been any change in the performance? |
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| Author: | ric [ Tue May 08, 2012 8:20 am ] |
| Post subject: | Re: RPM's |
Well the question has to be asked....What is the total combined weight of the 3 people? Are we talking about 3 average males @ around 550lb total or 3 healthy American's @ 1000lb with a full tank of gas, cooler, etc? If it's the latter... the H200 with a 4.3 isn't going to do it. |
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| Author: | SeriousRob [ Tue May 08, 2012 8:27 am ] |
| Post subject: | Re: RPM's |
Rotary Racer has a good point. The trim will affect the RPMs as well. Max RPM is at the proper trim level. The other weekend I was out and the RPMs veried by nearly 1000 when I properly trimmed the boat. Rob |
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| Author: | Dmoe103 [ Tue May 08, 2012 8:36 am ] |
| Post subject: | Re: RPM's |
I tried trimming the boat as high as I could to get the rpm's as high as I could at WOT. 2400 was it with the 19 prop. Total combined weight of riders was 550 lbs with a full gas tank and an ice chest (built in). Before I replaced the 21 prop with a 19 I did not pay attention to the max rpm. I know that the boat had about a 10 mph faster top end with the 21 prop. I am after more hole shot and don't care too much about top end speed. Just don't want to hurt the motor. |
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| Author: | ric [ Tue May 08, 2012 8:50 am ] |
| Post subject: | Re: RPM's |
At this point it's safe to say.... Your tachometer is broken. |
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