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| Did my boat come with the wrong prop? https://www.smwebhead.com/phpBB3/viewtopic.php?f=3&t=13445 |
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| Author: | simonj [ Thu Sep 04, 2014 8:38 pm ] |
| Post subject: | Did my boat come with the wrong prop? |
2014 H180 with the 4.3TKS First chance I've really had to open it up to WOT. 2 adults, 2 small kits, 3/4 tank of gas. Bimini top installed...but wasn't extended at the time. Not much gear on board beyond the standard safety kit. At WOT - i was seeing about 42mph on the speedo (didn't have my GPS with me) at just over 3000rpm. I know the 4.3 is supposed to rev up to around 4400? The prop is a BlackMax 14x23P. Its a pretty course pitch...which I understand is responsible for the lower revs at WOT - I'm happy with the top speed, as I mostly go out with my young family....but that aside, would there be any advantage to going to a lower pitch prop like a 19 or so? |
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| Author: | rpengr [ Thu Sep 04, 2014 10:25 pm ] |
| Post subject: | Re: Did my boat come with the wrong prop? |
Yes. 3000 rpm at WOT is so extremely low, that you may have a bad tachometer. One possibility is that your tachometer is set on 8 cylinder instead of 6 cylinder. That would make it indicate 25% low (meaning your 3000 rpm is really 4000 rpm). Another possibility is that the tach is just malfunctioning... not uncommon. If you are really only getting 3000 rpm, then you could be doing serious damage to your engine. This $35 multimeter with tachometer from Harbor Freight could tell you your real RPM http://www.harborfreight.com/lcd-automotive-multimeter-with-tachometer-kit-95670.html or something from your local auto parts store. Short of that, you can download a free app for your phone which can act as a tachometer based on sound (and telling it how many cylinders your engine is). So I would start by making sure your tach is correct. Even if you are only getting 4000 rpm, you should strongly consider a lower pitch prop. (21P) |
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| Author: | simonj [ Fri Sep 05, 2014 5:03 am ] |
| Post subject: | Re: Did my boat come with the wrong prop? |
Thanks for that....The tach settings is the first thing I'll check. I'll report back with what I find. BTW, the boat is brand new - only 14 hrs on it....I'd be a little miffed if the tach wasn't set properly from the factory. |
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| Author: | LouC [ Fri Sep 05, 2014 5:42 am ] |
| Post subject: | Re: Did my boat come with the wrong prop? |
It might be hard to see but on the back of the tach there is a button (small thing the you can put a small screwdriver in) the switch is marked for each engine type. Go on the Faria website and look in their tech section they probably have some pix of it in the instructions. Having the Bimini up will slow the boat down for sure. You want to get this right, if the max rpm for wide open throttle is not right it puts a big strain on the engine. My boat came with a 14.5x19 prop, it would only reach 4200 then, when I tried a 15x17 it pulled 4800 like it should. |
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| Author: | simonj [ Fri Sep 05, 2014 6:41 am ] |
| Post subject: | Re: Did my boat come with the wrong prop? |
Ok, so I checked the tach and it was on setting 4 - which according my FW manual...is for 12 pole applications (outboard engines?) So I switched it to setting 2 for 6 cyl. I'll report back to with the changes. Thanks all. |
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| Author: | rpengr [ Fri Sep 05, 2014 7:45 am ] |
| Post subject: | Re: Did my boat come with the wrong prop? |
That's great that you found the incorrectly set tachometer. 23P still sounds high for a boat that goes 42mph, but that depends on gear ratio. You will want to confirm speed with a GPS. (most boats I have heard of with 23P props are in the 50-70 mph range) Now that I looked it up on Harbor Freight, I am going to get one of the multimeter/tachometers, and that will be the multimeter that stays on the boat: http://www.harborfreight.com/lcd-automotive-multimeter-with-tachometer-kit-95670.html $35 We look forward to hearing your next results. |
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| Author: | babbot1 [ Fri Sep 05, 2014 11:07 am ] |
| Post subject: | Re: Did my boat come with the wrong prop? |
I bought one of these to validate my tachs. You can use it on anything. All you do is stick a piece of reflective tape on a rotating part and aim the laser at it. http://www.amazon.com/gp/product/B006V4WNYU/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1 Works great! I use it on everything from my electric drill press to lawn mowers to big engines. Just stick a piece of tape on the flywheel and your done, no need to worry about how many cylinders you have. I also have a tiny tach that I leave on my 9.9 outboard. It has been really handy but that has to be setup just like your tach on the boat. It can be used for many thing so a slightly off reading is possible and you wouldn't know without validating. |
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| Author: | simonj [ Sun Sep 07, 2014 5:10 pm ] |
| Post subject: | Re: Did my boat come with the wrong prop? |
Happy to report that everything now seems normal after the tach adjustment. With my family on board, full tank of gas, beach stuff etc...topped out at 46mph (Navionics GPS on my tablet) at about 4200 rpm I would say that sounds about right?? Odd that the tach would come from the factory like that? Oh well, quick fix...no harm, no foul. PS - eating up the last days of summer while they last!! 
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| Author: | LouC [ Mon Sep 08, 2014 5:58 am ] |
| Post subject: | Re: Did my boat come with the wrong prop? |
That's still a bit low, I'd want to see more like 4600-4800, each 1" drop in pitch gives you 200 rpm usually. I'd try a prop with 2" less pitch. On mine the 19 pitch prop gave me 4200, the 17 gives 4600-4700, I probably could have even gone to a 15 pitch.... |
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| Author: | simonj [ Mon Sep 08, 2014 6:15 am ] |
| Post subject: | Re: Did my boat come with the wrong prop? |
I agree Lou. But at least I'm now in the ballpark  The boating season is wrapping up in my neck of the woods and I'm planning on investing in an SS prop next year. I also plan on getting into skiing and wakeboarding, so I'll be looking for something to help with the holeshot. |
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| Author: | rpengr [ Mon Sep 08, 2014 9:59 am ] |
| Post subject: | Re: Did my boat come with the wrong prop? |
My guess is that with a 21P SST, you will top out around 50mph at 4700-4800rpm AND get better hole shot for towing. |
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