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| RPM question http://mudmotortalk.com/mmt_v2/viewtopic.php?f=3&t=2763 |
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| Author: | SmokeEater829 [ Tue Jun 23, 2009 3:49 pm ] |
| Post subject: | RPM question |
I am wondering if anyone on here can tell me what RPM's i should be getting out of my motor. I have a 35 GDSD with the EVT exhaust, and EXT intake/mikuni setup. I'm getting around 3950 rpms when I'm running. Wanted to know if this sounds right to you guys that know what ya'll are talking about. Also, I'd say my prop is about 90 - 95%. Had the GD 3 blade put on last year. I have about 65 hours since the prop was installed. |
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| Author: | aucoin [ Tue Jun 23, 2009 4:22 pm ] |
| Post subject: | Re: RPM question |
sounds about right.......if you could get a lil more that would be better, just try to stay under 4300 so you dont float a valve |
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| Author: | HuntingRDR [ Tue Jun 23, 2009 5:15 pm ] |
| Post subject: | Re: RPM question |
Sounds good. That is about what I am getting |
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| Author: | Gigafowl [ Tue Jun 23, 2009 6:35 pm ] |
| Post subject: | Re: RPM question |
GD 3 blade prop - measure across the blade - 3 1/2" wide new - under 3" - it's gone ! Prop wear has a bigger impact on holeshot and top speed than RPMs for me anyway. I'll turn an extra 100 or 200 RPMs and run 3 to 4 mph slower doing it. |
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| Author: | deadbird8 [ Tue Jun 23, 2009 6:37 pm ] |
| Post subject: | Re: RPM question |
With a carb and exhaust I would expect higher RPM. What were you running before you put them on? |
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| Author: | Gigafowl [ Tue Jun 23, 2009 6:49 pm ] |
| Post subject: | Re: RPM question |
PS - at 3950 RPMs solo my GDSD 16x48 is running over 30 mph with a good prop - and at 4100 RPM only 28 mph with a blade under 3 1/4" wide using the GD 3 blade props. Only about a 1/8" to 3/16" blade width difference in those two props ! ! ! At least those are the GPS speeds I ran this weekend while prop testing a totally stock 35hp GDSD on my 16x48 GDSD boat. |
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| Author: | SmokeEater829 [ Tue Jun 23, 2009 9:42 pm ] |
| Post subject: | Re: RPM question |
Before the updrades, i was running about 3580-3600. In my 16x54 i have seen 29.5 mph on the GPS, but the boat was porpsing so bad that i could barely keep the prop in the water. I can't get it to stop. Gas tanks are all the way in the bow under the deck. Only thing left in the back is me and the battery. |
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| Author: | rebbeer [ Wed Jun 24, 2009 7:35 pm ] |
| Post subject: | Re: RPM question |
Looks like it's time for some wedges. |
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| Author: | deadbird8 [ Wed Jun 24, 2009 7:52 pm ] |
| Post subject: | Re: RPM question |
| Author: | Gigafowl [ Wed Jun 24, 2009 8:22 pm ] |
| Post subject: | Re: RPM question |
Deadbird, I know what you are thinking - however the way that GDSD floats the transom angle is a non issue -unless the submersed fins are bent up excessively it never even touches the trim stop at those speeds - Coco puts that rear transom cut into his boats to help with pushing them backwards and you have to add some nose weight to get a smooth ride over 25 mph on several GD hulls... If SmokeEater adds a winch and moves his batteries up front - he will find the cure. Or carry a bigger ice chest up there - my GDSD 16x48 did it too - some SO cables and battery relocation did the trick on mine. Smooth as silk now over 30mph with stock 35hp GDSD. Was hoppin at 24mph and up till I found the balance needed. Wedges - bad idea in my book, just pure drag. |
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| Author: | rebbeer [ Wed Jun 24, 2009 8:32 pm ] |
| Post subject: | Re: RPM question |
Correct me if I'm wrong, but from what I understand wedges don't create drag, they actually pick up the back of the boat and help you stay on top of the water. |
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| Author: | Gigafowl [ Wed Jun 24, 2009 8:40 pm ] |
| Post subject: | Re: RPM question |
So do hydrolic trim tabs - but I would not want them on a mudrig - I'd rather look for a way to balance the stuff I am already haulin around instead. |
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| Author: | craig [ Sat Jun 27, 2009 5:56 am ] |
| Post subject: | Re: RPM question |
| Author: | marsh bandit [ Sun Jun 28, 2009 9:53 pm ] |
| Post subject: | Re: RPM question |
I have hit 32 multiple times with my rig and it has never wanted to porpuse. Hopefully I'll have the same luck with the new hull |
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| Author: | A5Mag12 [ Mon Jun 29, 2009 9:32 am ] |
| Post subject: | Re: RPM question |
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