SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: iloveitloud on March 28, 2011, 06:48:39 PM
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My question is pretty much, Is a 3/8 rubber line from the tank to the pump,-9 feet, limiting my fuel supply at high rpm? Boat is a high compression 454, with a 750 holley. Top rpm is about 47-4800, and it just feels like the motor has more in it, but just can't rev up any more.
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Do you have a rev limiter, fuel gauge, A impeller.....
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No rev limiter, no fuel pressure gauge, do have A impeller. Just barely got boat running last year, and was happy just to have that, so i did not get much time to tune it before winter. Summer is comming here, so I will be getting the boat out soon to start working on it.
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I would get a fuel gauge...that way you know. Have you done a tune up....all filters, plugs, wires, cap/rotor/dizzy, carb...ect. Not sure on BBC for timing but I would set that with 3000RPM and most idle at 1000-1200 out of the water. Under load in water your rpm will drop about 200rpm.
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Fuel gauge is the first thing I will do. Has newer Mallory Unilite distributer, and Taylor 8mm wires. I have not even checked timeing,--I just put the distributer back in where it was when I re-built the motor, and it ran the same as it did before the motor spun a bearing. I'll be getting it out soon, and have more info.
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When I was carb'd. I ran -10 lines and then -8 lines to the bowls. I now run -12 lines out of the tanks including 3/4" ID custom made pickup tubes then from the pump to the fuel rails -10.
T.J.
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I'm a bit fuzzy on -line sizes. Are they measured in milimeters?... So a -10 would be 10 mm, -20 twenty mm, and so on?
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http://www.gre6.com/ansize (http://www.gre6.com/ansize)
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Fuel gauge is the first thing I will do. Has newer Mallory Unilite distributer, and Taylor 8mm wires. I have not even checked timeing,--I just put the distributer back in where it was when I re-built the motor, and it ran the same as it did before the motor spun a bearing. I'll be getting it out soon, and have more info.
Setting the ignition timing is critical to performance and engine life.
3/8" fuel is -6 in AN line size, and adequate for a regular 454... AS LONG AS THE LINE IS NOT SOFT AND ABLE TO COLLAPSE.
I actually ran a 632 cu in engine on the dyno with two carbs fed with a single -6 (3/8") fuel line from the fuel pump to a -6 tee that fed two 850 cfm Quick Fuel carbs, to 6300 rpm. I had plumbed it with a -8 but had a bad tee fitting, and had to use something else to be able to run the engine, no drop in pressure or signs of fuel starvation.
Based on that, I would say your 3/8" line is fine for a 454 running 5000 rpm.
For a forced induction engine (blown or turbo), I would normally use larger lines, and agree with the -12 feeds from the tank into a tee,, allowing the tanks to equalize.
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It is my humble opinion (and I like the sound of my own voice :P) that the line sizes depend on what type of fuel pump.
You can run smaller fuel lines with an electric gear pump, but a diaphragm mechanical sometimes requires a bit more line size because of the pulse of the fluid.
I think 3/8" is adequate in most cases, I would totally advise using USCG approved fuel hose though.... ;)
GT
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It is my humble opinion (and I like the sound of my own voice :P) that the line sizes depend on what type of fuel pump.
You can run smaller fuel lines with an electric gear pump, but a diaphragm mechanical sometimes requires a bit more line size because of the pulse of the fluid.
I think 3/8" is adequate in most cases, I would totally advise using USCG approved fuel hose though.... ;)
GT
I'm with Glen on this. Again........ I doubt very seriously that a 3/8 fuel line is the problem. Soft or not, ( it would act like it's out of gas at speed, or hiccup like crazy, if it were soft or not big enough ;) )
I've seen a 3/8 rubber fuel line feed a blown twin dominator deal! So forget that BS! :P
You forget to mention what dizzy you have. I'd be more apt to beleive a vacuum advance, or another substandard unit. If the HP is there to drive an A to 5000-5500 RPM, then only the ignition, or remotely, possibly, the valve springs, are limiting you, all else being equal.
Get yourself a good Dizzy (Prior, PRE-TDRSALES days, these guys would say go MSD..........I say go Mallory Unilite) A good CDI Box, If you go Mallory, no better than their Hyfire 6AL.
At worst, if I'm wrong, you have a solid ignition for the right combination. All this provided you have the HP to turn an A to 5000+ RPM, mind you. THAT is paramount...........
Ray
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If you are in doubt go with a fuel return system it works great , keeps the fuel supply charged all the time.
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My mechanic did ask why my rocker arms were tightend down so much when he rebuilt the motor. He asked if I was doing it as a rev limiter. I did not know they were "tight", as I never had the motor apart before. Anyway, he put them back the way they were, so that could be part of the problem.
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IMHO! Wherever you are, find an engine guy that is willing to help you with the basics. A couple of hours tuning could really help you. Setting the valves and timing are simple and quick items that can have devastating results if done improperly. I am in Vegas and would be willing to work for food. A little help will go a long ways.
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Is it worth the extra cost of buying marine fuel line over just fuel line for cars?
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Is it worth the extra cost of buying marine fuel line over just fuel line for cars?
Technically, USCG fuel hose is a requirement.....And yes, worth the dough IMHO, I am addicted to breathing and allergic to fire.... :sly:
GT
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Technically, USCG fuel hose is a requirement.....And yes, worth the dough IMHO, I am addicted to breathing and allergic to fire.... :sly:
GT
I like how you put that Glenn! :thumbup:
This is the factory hose on Moo, but I haven't seen any USCG rating on it....... :sly:
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi673.photobucket.com%2Falbums%2Fvv95%2FIrrebel%2FMoo%2520build%2FFuelvalve.jpg&hash=33922dc35fb49e17568d6035df86774e99f9490c)
Ray
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I like how you put that Glenn! :thumbup:
This is the factory hose on Moo, but I haven't seen any USCG rating on it....... :sly:
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi673.photobucket.com%2Falbums%2Fvv95%2FIrrebel%2FMoo%2520build%2FFuelvalve.jpg&hash=33922dc35fb49e17568d6035df86774e99f9490c)
Ray
I believe the red stripe gives it away, does have an SAE number on it? Like J1527 or similar? Fuel hose has gone through somewhat of a metamorphoses since the addition of MTBE, so labeling may have changed...
GT
Rechecked...MPI=Marine Products International..... :sly:
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If I remember correctly back in the days when I worked at the Phoenix Sea Ray plant then the red stripe is the marine stuff. Just wondering and the boat I bought just has the vehicle fuel line in it.
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A car engine, or a boat engine rebuilt by a car shop, in a jet boat will usually only run 45-50 mph. Car engines have smaller valves, less compression, and even the most popular "RV" cam used by the car guys is much smaller than the stock jet boat grind. As far as dists go, read my post in the need "copper wires", it may explain a lot. A boat also needs less fuel line and pump than a drag/ street car because the tanks in a boat are even with or in front of the engine and much closer, so the fuel doesn't need to be pulled foward against the "G" load of the launch for 12 feet. Check the cam and dist. TIMINATOR