Does prop slip increase or decrease with speed? Top speed less than expected.
11-25-2014 | 05:41 PM
#151
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From: Northport N.Y.
If you have the bypass pluged and running a short oil filter with no bypass that is very bad. My buddy's shop gets blown up motors all the time from the non performance oil filters. Put a wix racing equal to a hp6 remote mount with the bypass.
Last edited by 14 apache; 11-25-2014 at 05:44 PM.
11-25-2014 | 08:36 PM
#152
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Apache, I saw some people running the Baldwin 1441 filter that is supposed to have a bypass. Guess I'll have to get the WIX catalog out and look for the largest filter I can fit under there that has a bypass built into it.
And yes, some of the pleats were pushed together.
And yes, some of the pleats were pushed together.
11-25-2014 | 10:21 PM
#154
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From: On A Dirt Floor
Cut filter open, and no sign of bearing debris. Going to try to find a way to wedge a larger oil filter in there, as the stringer location had limited me to one of the short filters. What WIX / NAPA Gold number are most of you all running? Looking for something that is not more than about 5 inches long, as I don't think a bigger filter will wedge in there.
Beta Ratio : 2/20=6/20
Filter O.D. (Inches) : 3.66"
Flow Rate : 9 - 11 gpm
Gasket I.D. (Inches) : 3.1"
Gasket O.D. (Inches) : 3.444"
Height (Inches) : 5.178"
Media Type : Glass Enhanced Cellulose
Micron Rating : 21 Micron
Style : Spin-On Lube Filter
Thread Size (Inches) : 13/16 - 16
Burst Pressure : 270 psi
Filter O.D. (mm) : 93 mm
Gasket I.D. (mm) : 79 mm
Gasket O.D. (mm) : 87 mm
Height (mm) : 131 mm
11-25-2014 | 10:23 PM
#155
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Posts: 14,090
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From: On A Dirt Floor
Here are specs of that one.
51060R
Product Line: NAPA Gold Filters
Features & Benefits
High Performance Racing Filter w/ T-71 Racing Media That Lowers Restriction & Increases Horsepower; Use For Racing Applications Only - Not For Street Use; Contains Anti-Drain Back Valve - If No ADBV Required, Use # 51061R
Attributes
Filter O.D. (Inches) : 3.6"
Flow Rate : 28 gpm
Gasket I.D. (Inches) : 3.1"
Gasket O.D. (Inches) : 3.44"
Height (Inches) : 5.17"
Media Type : Glass Enhanced Cellulose
Style : Spin-On Lube Filter
Thread Size (Inches) : 13/16 - 16
Filter O.D. (mm) : 91 mm
Gasket I.D. (mm) : 79 mm
Gasket O.D. (mm) : 87 mm
Height (mm) : 131 mm
51060R
Product Line: NAPA Gold Filters
Features & Benefits
High Performance Racing Filter w/ T-71 Racing Media That Lowers Restriction & Increases Horsepower; Use For Racing Applications Only - Not For Street Use; Contains Anti-Drain Back Valve - If No ADBV Required, Use # 51061R
Attributes
Filter O.D. (Inches) : 3.6"
Flow Rate : 28 gpm
Gasket I.D. (Inches) : 3.1"
Gasket O.D. (Inches) : 3.44"
Height (Inches) : 5.17"
Media Type : Glass Enhanced Cellulose
Style : Spin-On Lube Filter
Thread Size (Inches) : 13/16 - 16
Filter O.D. (mm) : 91 mm
Gasket I.D. (mm) : 79 mm
Gasket O.D. (mm) : 87 mm
Height (mm) : 131 mm
11-26-2014 | 06:57 AM
#156
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I think I'm going to break the oil filter discussion off into another thread, as I think it might benefit some other folks who have their bypasses plugged. Going to look through Arctic Friends' thread first to see if it was addressed. If not, and we get some good info / discussions, maybe the mods would want to tack it on.
11-26-2014 | 08:16 AM
#157
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From: Chicago
Thinking my plan at this point should be to put that 6-valve mechanical pump on there with a 1/2" line feeding it, along with a new 1/2" pickup in the tank.
Two questions - anyone running the composite fuel pump rod on a billet cam?
Anyone have a good source for a tank pickup, or should I plan on having one fabricated from aluminum tubing?
Two questions - anyone running the composite fuel pump rod on a billet cam?
Anyone have a good source for a tank pickup, or should I plan on having one fabricated from aluminum tubing?
I thought the baker pump was a really nice piece yet I was running out of fuel pressure at 6000rpm but on that pump only.. take those results with a grain of salt however because one of my tanks was out of commission so I was sucking out of a single tank. Possibly too much fuel going out not enough vent. But then why was the Holley on the other motor fine? Ill figure that out next year.
Had I known about the light weight rod I would have used it.
I found my pickups at one of the custom aluminum fuel tank manufacturers but can seem to find the link now..
11-26-2014 | 12:51 PM
#158
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From: Beaverton Or
I ran my boat Sunday for what I was planning to be the final run for the season and finally had a chance to really crack on it before it went on the trailer. Seems like I always had a crapload of people on board every other time I had it out this year, so I went easy on it for most of the season. Top speed was considerably less than anticipated. I plugged in some numbers into the go-fast.com prop slip calculator, and I got the following slip calculations:
I am running a 1.36 Bravo 1 with a Mirage Plus 23. Boat is a 1988 Baja Force235 with a 489 running AFR heads, Holley 800, Lightnings, etc. This build has been pretty well documented on other threads here, so most of us are familiar with it. I had the engine dynoed and saw 585 HP at 5400 RPM and between 575-600 ft lbs of torque all the way from 3000 RPM up to peak HP.
At 3000 RPM I was seeing about 39 MPH on GPS. Theoretical MPH at this RPM is 49, so I have a slip factor of around 19% at this speed. Fair enough, there is a lot of hull in the water at this speed.
At 3500 RPM speed was showing about 48 MPH on the GPS. That equates to a slip factor of 14%, which is pretty much as expected.
I ran it on up to WOT, and was only able to make it to 61 MPH. RPM was only 4600, and that comes out to a slip factor of 18%. Something seems amiss here, both from the higher slip number and the fact that I wasn't able to spin this thing faster. I played around with trim and tabs, but did not seem to make a difference on top speed. Why would my slip number go up, unless I had it over trimmed?
It seems to be making plenty of power at lower speeds, getting up to 50 MPH is pretty effortless, so engine seems to be running OK. Did not note any miss or notice that it seemed to be running poorly, but it just wasn't bringing the power. Dyno runs were made with dry dyno headers, and A/F numbers were around 13 from 4000-5000 RPM, so I would expect it to run a little richer with the wet exhaust and muffler tips on it. I have yet to check the easy stuff like throttle opening all the way (it was with the other engine, and nothing changed in this regard), timing, etc. I was running speeds like this with a 454 that made less than 400 HP, so I would have to be dropping at least 100 HP if it is an issue with the engine.
Anyone want to take a stab at it? Maybe my boat is just a pig!
I am running a 1.36 Bravo 1 with a Mirage Plus 23. Boat is a 1988 Baja Force235 with a 489 running AFR heads, Holley 800, Lightnings, etc. This build has been pretty well documented on other threads here, so most of us are familiar with it. I had the engine dynoed and saw 585 HP at 5400 RPM and between 575-600 ft lbs of torque all the way from 3000 RPM up to peak HP.
At 3000 RPM I was seeing about 39 MPH on GPS. Theoretical MPH at this RPM is 49, so I have a slip factor of around 19% at this speed. Fair enough, there is a lot of hull in the water at this speed.
At 3500 RPM speed was showing about 48 MPH on the GPS. That equates to a slip factor of 14%, which is pretty much as expected.
I ran it on up to WOT, and was only able to make it to 61 MPH. RPM was only 4600, and that comes out to a slip factor of 18%. Something seems amiss here, both from the higher slip number and the fact that I wasn't able to spin this thing faster. I played around with trim and tabs, but did not seem to make a difference on top speed. Why would my slip number go up, unless I had it over trimmed?
It seems to be making plenty of power at lower speeds, getting up to 50 MPH is pretty effortless, so engine seems to be running OK. Did not note any miss or notice that it seemed to be running poorly, but it just wasn't bringing the power. Dyno runs were made with dry dyno headers, and A/F numbers were around 13 from 4000-5000 RPM, so I would expect it to run a little richer with the wet exhaust and muffler tips on it. I have yet to check the easy stuff like throttle opening all the way (it was with the other engine, and nothing changed in this regard), timing, etc. I was running speeds like this with a 454 that made less than 400 HP, so I would have to be dropping at least 100 HP if it is an issue with the engine.
Anyone want to take a stab at it? Maybe my boat is just a pig!
https://www.daviscoltd.com/Engineeri...ler_course.pdf
To avoid cavitation, first reduce the RPM of the prop. This requires higher pitch and perhaps a
different gear ratio. Reduced RPM may also require a propeller too large to fit under the boat. In
this case, increase the loaded area of the propeller by increasing blade area ratio or the number of
blades. Finally, cupping acts like increased pitch, but also acts to suck the cavitation bubble.
This is exactly what i ran into with the Mirage i just never gave it any thought. The original dive was a alpha on with a 1.32 which had a small run in with a rock...Replaced it with a SEI 1.47 ratio and a 23p 4blade prop two thing's happened slip went to 10% and the boat was much smoother..which i know assume was the old props cavitating badly.
19p @ 5000 with 1.32 =prop rpm
[email protected]=3787......actual prop rpm
3787 div 60=63
63x4= 252 ft per sec
23p @ 4400 with 1.47 = prop rpm
[email protected]= 2993....actual prop rpm
2993 div 60=49
49x4=200 ft per sec
That's some meatball calc's but show's a big drop in prop rpm about 20% slower in rotational speed. 15" diameter prop.
Need to get a calc..
https://www.youtube.com/watch?v=N3WwQKZ05Uk&feature=player_detailpage
Last edited by Pliant; 11-26-2014 at 02:24 PM.
11-26-2014 | 09:20 PM
#159
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Joined: Apr 2006
Posts: 977
Likes: 25
From: Palm Harbor, FL
Just a wild guess but I'd think the replacement drive and prop you tried was a 1.36 as well...change the ratio and use your current prop and you will be close. Just for giggles run the prop calculator with same prop number with the 1.5 ratio and see what your estimated numbers are.
