Does prop slip increase or decrease with speed? Top speed less than expected.
10-30-2014, 10:46 AM
#61
Would the blue pump suffice for my application? I see it comes with a regulator - does that require a return line plumbed back to the tank? What's the difference between the standard and the marine version, besides the overflow fitting?
10-30-2014, 10:54 AM
#62
In regards to the drive ratio / prop issue, I feel like I pretty much covered that one years ago with my 454. I swapped to a 1.5 drive with a 23 M+, and saw no difference in speed. I really don't think that's the problem here.
For comparison, my buddy is running the identical hull with an HP500 clone with Lightning headers, 800 Holley, Dart intake, etc. He is running a 1.5 Bravo 1 with a 25 Mirage Plus, and is seeing around 71 MPH. That is the range that I was expecting this combo to run in.
For comparison, my buddy is running the identical hull with an HP500 clone with Lightning headers, 800 Holley, Dart intake, etc. He is running a 1.5 Bravo 1 with a 25 Mirage Plus, and is seeing around 71 MPH. That is the range that I was expecting this combo to run in.
10-30-2014, 11:25 AM
#63
Thanks, I appreciate the good thoughts. At this point I just want to get it running right, and will be happy with upper 60's / lower 70's. Never was my intention to go for max speed on this thing - hell, the argument could be made that I should have just built a stock motor for this particular boat. Motor is probably worth more than the boat.
10-30-2014, 12:40 PM
#64
Lastly, I feel the 1.36 drive and a 23" prop is a less than desirable combination. The blade tip speed at WOT for a 23" Mirage and 1.36 gears will be excessive in my opinion and inefficient. I know it's not cheap but 1.5 gears starting with a clean 21" Mirage + and working up to a 23" might be a better solution.
10-30-2014, 12:54 PM
#65
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Bud, easy way to tell if you have a fuel delivery issue is run it wide open for a mile or so and then back of the throttle a little. If you feel the power come in when you back off the throttle there is a delivery issue. The stock pickup in the baja tank where it 90's out of the tank has a hole smaller than the one in the end of my PP. when I put the 496 in my baja and held it wide open for any amount of time the motor would literally shut off. I put a 5/8 pickup in it and never shut off on me again...
10-30-2014, 01:26 PM
#66
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I cant help myself looking at this thread it is the same issue i had. The only constant is slip irregardless of power applied or speed aside from a small bump at mid wot then falling back at high wot. Hull issue aka dirty...hook...something etc....prop hub a simple grease pen mark takes that issure away...and last prop those are the constant's that create slip...and bad coupler would being smoking Not???..The engine still has enough power to push to 4600. Put the slip into something acceptable say 12% and you get 65 mph now scale that up to 5400 you get 74 again. I know this may sound borish but how high was the hull riding at wot. IT would take a lot of drag to pull down both that engine and a mirage prop and it reads just like that.
I dont understand if your running lean why she has not popped thourgh the carb..now if you were rich then it makes sense. Or the timing is very retarded.
I dont understand if your running lean why she has not popped thourgh the carb..now if you were rich then it makes sense. Or the timing is very retarded.
Last edited by Pliant; 10-30-2014 at 01:30 PM.
10-30-2014, 01:28 PM
#67
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A couple of observations. Looking at your dyno run you are only making around 520 HP at 4600, so you're leaving around 70 HP on the table by not getting the rpm up to 5500. Second, I've built and dyno'd many engines both in and out of the boat (I have a prop shaft dyno) and my engine dyno can run wet exhaust. I have found you lose 20-30 HP going from dry dyno headers to the wet lightnings. So, that combination puts you about 100 HP less than your dyno numbers. I have always found engines to run richer in the boat than on the dyno. Generally about .5 A/F numbers. The wet exhaust will richen it up some too. I've dyno'd engines on the engine dyno, then installed them in the boat and re-dyno'd them at the prop. They always got richer. They also lose right at 10% power from the drive. Another thought, if you have any mufflers on your boat, that could cost some HP. You really need to get an 02 sensor and tune it in the boat.
Bob Lloyd
Bob Lloyd
10-30-2014, 02:27 PM
#68
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i think we are missing the fact, that this boat ran very close speeds to what it is now, with the engine it had in it! Which if I remember, was a 330HP 454 with a couple tricks? He didn't buy the boat without power, he didnt change x dimensions, gear ratios, any of that. He simply built up his engine.
The engine made power on the dyno, 585hp...and his torque was also very respectable thruout the range. What changed from the dyno? Well, he wasnt running that fuel pump, he wasnt sucking thru the baja tank pickup, the filter assembly, nor the fuel lines that are in the boat. Any of those things could present an issue.
I personally, would never begin chasing prop issues, gear ratio changes, prop depths, and a whole bunch of other things, without positively verifying that the engine, is in 100% state of tune.
A simply fuel pressure verification, would rule out fuel delivery starvation issues. I would go there before doing anything else. I've have seen many times, where fuel delivery issues dont always result in backfires, or things of that nature. I've seen pistons get melted with giant holes, without one indication that something was amiss. I would not risk melting an engine down, based on "it should be getting enough fuel, or it should be jetted ok", or "I think the timing is where its supposed to be", and go chasing prop slip issues and things of that nature first.
I agree that installing a wide band would make his life easier, and really tell a good story on whats going on.
The engine made power on the dyno, 585hp...and his torque was also very respectable thruout the range. What changed from the dyno? Well, he wasnt running that fuel pump, he wasnt sucking thru the baja tank pickup, the filter assembly, nor the fuel lines that are in the boat. Any of those things could present an issue.
I personally, would never begin chasing prop issues, gear ratio changes, prop depths, and a whole bunch of other things, without positively verifying that the engine, is in 100% state of tune.
A simply fuel pressure verification, would rule out fuel delivery starvation issues. I would go there before doing anything else. I've have seen many times, where fuel delivery issues dont always result in backfires, or things of that nature. I've seen pistons get melted with giant holes, without one indication that something was amiss. I would not risk melting an engine down, based on "it should be getting enough fuel, or it should be jetted ok", or "I think the timing is where its supposed to be", and go chasing prop slip issues and things of that nature first.
I agree that installing a wide band would make his life easier, and really tell a good story on whats going on.
10-30-2014, 03:59 PM
#69
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i think we are missing the fact, that this boat ran very close speeds to what it is now, with the engine it had in it! Which if I remember, was a 330HP 454 with a couple tricks? He didn't buy the boat without power, he didnt change x dimensions, gear ratios, any of that. He simply built up his engine.
The engine made power on the dyno, 585hp...and his torque was also very respectable thruout the range. What changed from the dyno? Well, he wasnt running that fuel pump, he wasnt sucking thru the baja tank pickup, the filter assembly, nor the fuel lines that are in the boat. Any of those things could present an issue.
I personally, would never begin chasing prop issues, gear ratio changes, prop depths, and a whole bunch of other things, without positively verifying that the engine, is in 100% state of tune.
A simply fuel pressure verification, would rule out fuel delivery starvation issues. I would go there before doing anything else. I've have seen many times, where fuel delivery issues dont always result in backfires, or things of that nature. I've seen pistons get melted with giant holes, without one indication that something was amiss. I would not risk melting an engine down, based on "it should be getting enough fuel, or it should be jetted ok", or "I think the timing is where its supposed to be", and go chasing prop slip issues and things of that nature first.
I agree that installing a wide band would make his life easier, and really tell a good story on whats going on.
The engine made power on the dyno, 585hp...and his torque was also very respectable thruout the range. What changed from the dyno? Well, he wasnt running that fuel pump, he wasnt sucking thru the baja tank pickup, the filter assembly, nor the fuel lines that are in the boat. Any of those things could present an issue.
I personally, would never begin chasing prop issues, gear ratio changes, prop depths, and a whole bunch of other things, without positively verifying that the engine, is in 100% state of tune.
A simply fuel pressure verification, would rule out fuel delivery starvation issues. I would go there before doing anything else. I've have seen many times, where fuel delivery issues dont always result in backfires, or things of that nature. I've seen pistons get melted with giant holes, without one indication that something was amiss. I would not risk melting an engine down, based on "it should be getting enough fuel, or it should be jetted ok", or "I think the timing is where its supposed to be", and go chasing prop slip issues and things of that nature first.
I agree that installing a wide band would make his life easier, and really tell a good story on whats going on.
Opps's missed that:" i think we are missing the fact, that this boat ran very close speeds to what it is now" That's intresting since the gearing is the same i assume the slip was the same...18%?? If so another constant.
Last edited by Pliant; 10-30-2014 at 04:22 PM.
10-31-2014, 12:06 AM
#70
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Budman, as I'm chasing similar problems as you my first problem was the Holley red fuel pump that came with my boat that spec'ed out at 97gph, but in fact I was getting 4psi at idle and could watch it dip even further with a blip of the throttle. Went back to the OEM mech pump and gained 6mph right there. Electric pumps have been flogged to death here, and in collective experience they just can't handle the crap that comes through the fuel tank of a boat.
I'm just sharing my experience.
I'm just sharing my experience.
