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View Full Version : WOT RPM for '91 351W Indmar


davekro
08-02-2007, 02:43 PM
What is the recommended Wide Open Throttle RPM range for the 1991 351W Indmar motor? I think I need this to determine the proper Acme size/pitch prop to replace my OJ Legend 4 blade 13x13.

In my '91 PS 190, I am thinking of making the jump from OJ Legend 4 blade to new Acme CNC 3 blade prop. TRBeng (thanks for all your input!) notes he noticed a significant improvement from his OJ 4 blade to Acme CNC 3 blade.

Have others also seen significant improvement from OJ 4 blade to Acme 3 blade (in similar 240? HP engines)

Thanks, Dave

pram
08-02-2007, 02:45 PM
I changed from a 3 blade and went to a 541 this year and couldn't be happier. Flattened the wake, improved hole shot, no loss in top end, smaller rooster tail. Over all a much better prop than the stock OJ 13x13 that I had on it.

davekro
08-02-2007, 02:56 PM
Prambold,
Interesting. I never thought of a change to the wake. I don't recall if I had one many years ago when I went from OJ 3 to OJ 4blade. Like your change, I noticed much better hole shot, w/ no noticeable top end loss (maybe from 43 to 42MPH). So how did you decide on the #541 (13x12)?

Anyone with '91 - '93 PS 190 hulls notice a slalom wake improvement with Acme?

Dave

TRBenj
08-02-2007, 03:03 PM
The PCM and Indmar 240hp 351w's should be almost identical internally, and PCM's recommended max RPM is 4400. I believe that has more to do with the powerband of the motor than it does with reliability, as the stock headed 351w runs out of breath pretty quick. There is no difference in the block of the HO motor (285/300 hp) to justify the higher RPM rating (4800), the GT40 heads simply allow the engine to breathe better. Personally, I have no worries spinning my motor to 5200+ (which was originally a 240hp PCM).

When I added the 3-blade Acme to my stock motor, I gained 200 RPM due to the lower pitch (4600). Overall performance improved: holeshot, midrange responsiveness and top end.

davekro
08-02-2007, 03:10 PM
TRBenj,
Very glad to hear your Acme 3 blade improvement comments wee based on your stock engine (prior to engine mods)! I had assumed you added the Acme after going to your much higher HP mods.

We do have different hulls, but did you happen to notice any wake change going from OJ 4 to Acme 3 blade?

dave

TRBenj
08-02-2007, 03:40 PM
TRBenj,
Very glad to hear your Acme 3 blade improvement comments wee based on your stock engine (prior to engine mods)! I had assumed you added the Acme after going to your much higher HP mods.

We do have different hulls, but did you happen to notice any wake change going from OJ 4 to Acme 3 blade?

dave

I knew the Acme was the single best upgrade I could do (and the best bang for the buck), so I did it first. No regrets there.

I only skied the OJ a few times before switching and I didnt notice a difference. I dont remember there being a difference when we went to the 4-blade Acme from the OJ on our previous boat either.

butter
08-02-2007, 06:31 PM
The recommended max RPM is 4600.

(According to the '91-'93 owner's manual available here... http://www.mastercraft.com/manuals/1991-1993_OwnersManual-PS190-PS205-ProSport205.pdf)

davekro
08-02-2007, 08:39 PM
Butter,
Thanks for the PDF. I just got back from a test drive for max rpm and speed. With my '91 PS 190, OJ Legend 4 blade, driver only,
Perfect Pass: 4270 rpm, 42.4 mph
Analog gauges: 4200 rpm, 40 mph
I didn't think until I was out there I should have brought the GPS. ;o)

I rarely run flat out, and only for a few minutes, if I do. It has 1650 hours so I like to take it easy as far as not running flat out much. I wonder if a new prop allowed higher rpm's if that would improve low, mid range and higher end performance? This must be essentially what happened for TRBeng going from 4 blade OJ to 3 Blade Acme CNC where he got 200 more rpm's at the top end on his (stock) 351W.

EJ OJPROP
08-03-2007, 08:08 AM
Davekro - Has your current propeller been repaired? A stock OJ 13 X 13 LC 1" FORCE 4-blade should allow the motor to turn 4600 RPM. Increase in speeds are relative to pitch changes and number of blades. 3-blades are faster than 4-blades, regardless of who makes them. Lower pitch propellers will have better low end than higher pitch propellers.

123src
08-03-2007, 07:35 PM
Dave,

I just returned from the prop shop with a shiny new Acme 541in my hands! I have a 92 PS 205 and currently have the good ole repaired OJ 13X13 on it. I am going to spend a week on a lake starting next Monday, so I will fill you in on what changes I noticed. I will put the new prop on after the first few ski runs of the trip, so I can better judge any difference. If you don't see me post back on this in a week or so, PM me to remind me.:)

TCrate
08-03-2007, 09:02 PM
Keep in mind higher RPM's equate to more fuel consumption.

T-Rager
08-03-2007, 09:21 PM
I have a 1990 ProStar 190. I switched to the Acme 541 three years ago and experienced the same benefits that Prambold listed. Many others have reported the same findings on this forum. I believe that this prop switch is the single best and most cost-effective performance upgrade that you could make to your boat.

I have not actually tested WOT rpm on my boat as it's either idling or running 36 MPH.

davekro
08-11-2007, 02:34 PM
EJ OJPROP,
Yes my current 4 blade OJ Legend 13x13 has been repaired.
I would assume the rpm a given prop 'should' produce would depend on the HP of the engine driving it (assuming compared to the same or similar hull). Additionally, wouldn't a bigger or heavier boat, affect WOT rpm of a given size/pitch prop for a given HP engine?

So my engine being (1650 hr.) 240 HP, may not have the ponies to get the OJ 4b 13x13 up to 4600 rpm, whereas as a newer 300+ HP may get that??

Dave

123src
08-11-2007, 07:42 PM
OK>>>> Back from a week on the lake with the 541. All I can say to sum it up is "OUTSTANDING"! Better hole shot, faster top end, nicer wake. Best upgrade I have made on my boat!

davekro
08-11-2007, 08:21 PM
123src,
Thanks for the report!
What HP is your engine?
Was your (old) 13x13 OJ a 4 blade? If so, I am looking forward to testing with a friend on his '87 PS 190 with a brand new 351 GT40 engine just broken in. He ordered a 541 (3b 13x12.5), a 209 ( 4blade version of the 541), and a 475 (3b 13x12.625). Propellers on line thought the slightlt higher pitch would be better suited to his new higher HP (≈280 I think??).

It sounds like I will be buying the 541 off of him, having your comment replicate TRbeng's earlier. We'll be swapping/testing next week end. My friend is having a hard time 'believing' the 3 blade Acme does not lose any smoothness or drivability (his word) over the 4 blade.

He 'thinks' he will actually like the recommended 13x2.625 (475). So I may get my 541 this week end. :o)
Dave

davekro
08-11-2007, 08:24 PM
123src,

I forgot to ask... did you happen to notice your WOT rpm and speed (gauge or GPS)? Or what your old prop WOT rpm/speed was.

tks, Dave

123src
08-11-2007, 09:43 PM
OK, here are the answers to your questions.
Regular 351, not HO.
Old prop is a freshly repaired 3 blade OJ 13X13. (I have 3 of these if anyone is looking for one to buy!)
WOT (like you, not something I do very often) this weekend, at elevation (2,600 feet, though I live at sea level or so), 3 people in boat, RPM:
OJ ~3900
Acme ~4300

Speedo's not very accurate (they have both been cleaned out, but they read differently... I need to zero them in), but reading at least 3-4 MPH faster with the ACME.

And, don't forget, the hole shot is noticably stronger. :D