What fuel pump for a 502 making 600+hp.
 

I have a 502 I punched 10 over making 600+ on the dyno. We made many pulls to 5500 rpm with more to go but I would not let the shop owner keep going since I was not going to be running more then 5250 max. OK so on the dyno we used his fuel system (electric pump). I came home and put the stock bravo raw water pump on the motor with the mech fuel pump. No mater what prop I put on I could not get over 4700-4800. Well I always change the impeller every year and found gas in the pulley oil this year. So time for a new fuel pump.

Sorry to be long winded so here is the point. Now I was thinking of what if I was not getting enough fuel on the top end keeping me from getting the R's? What pump would you guys suggest I run. I have found other stock pumps for not much money 55 bucks but at 40 GPH are they pumping enough fuel for me? Should I go electric? I am open to ideas and am not looking to brake the bank since I might have to sell the boat soon. Until then I would like to use it and once I start using it I wont want to sell it.

I should add I have a worked 950QF carb opened up a bit.

Looking for advice and or if you think going larger on the fuel GPH will help me brake the wall I seam to have hit at 4800. Thanks in advance.

Motor started life as a 1994 502 mag gen V. This is the pump I have found from looking on this site others have used for stock motors. Airtex 60932

some gas in the oil cavity is not uncommon.the lube should be changed when you do the engine oil change.i did a 600 hp 518 cu in engine and used the stock 502 pump with great results.

I was told if gas was in that oil then the fuel pump was bad. I had no issues when it was running. Just could not hit the R's I wanted in the water. I was hoping I found the lucky fix. LOL

So is there a way to know if the fuel pump is bad? It has 500 hours on it and is 22 years old. I will say it was a lot of gas in the oil. Mostly gas. But then again I have never changed it. I will admit I had no clue it had oil in it. Some boater I am.

So do you think my fuel pump is bad?

May be cheap insurance to change it, however as Mike T said, those stock fuel pumps will support your need. I know several that are over 600 on the factory pump. If it's not bypassing fuel like the diaphragm is punctured, I doubt that the pump is the issue.

Add a fuel pressure gauge if you're nervous, they're a sound investment.

I ran the stock pump at 600 hp and 5500 rpm all day no issues.... you have another issue somewhere or a bad pump... be careful you can burn it up easy....

Thanks guys I will get a new pump cant hurt. I think it just needs more carb but who knows.

500 hours 22 year old it has to go.These pumps support 525sc also (600sc I believe) that use as much if not more than what a 600hp NA motor would.

one possibility is the dyno exhaust was far superior to the manifolds you have on the engine in the boat. does 502 mag use 454 mag exhaust or gils? gils should be fine. 454 mag exhaust runs outta gas around 400 hp.

What about the rest of his fuel system? I have a lengthy thread on here devoted to the supply lines and tank pickup to support my NA 489 that is making similar power. I had similar symptoms as his with Lightning headers, and the fuel pressure gauge confirmed that I was not getting a steady supply of fuel to the carb. I was advised that the stock 3/8" lines are not adequate for power levels approaching 600+ HP, although some OSO'ers had run stock lines with no issues. Sac Solutions, does your tank pickup still have the stock anti-siphon fitting on it? These can malfunction and be a source of restriction.

But Derek makes a good point - if he is trying to run a motor like this with stock Merc exhaust, he is going to have plenty of trouble getting it to make power on the top end, not to mention the possibility of reversion.

I am running EMI Thunders with the 16 inch ss tops. After that there is a short run to the back of the boat(7inches). Its wide open in the back. I am dumping a ton of water and was thinking it could be choking off my exhaust?! I do have stock stuff in the tank as far as I know. I do have a fuel pressure gauge on the duel feed line to the carb. I think it is saying 7.5 ish if I can remember.

At the dyno last year we did the brake-in runs and after the first two pulls the shop owner pulled the exhaust off and switched it out for a brand new set of headers. He claimed no way that motor made that HP from what I told him was in it. :blahblah: After tell him the work into it and not just bolt on parts and an exhaust change we pulled again. Loads of tuning a day later we got her dialed in and I got a handshake. Good job son that is one heck motor for your first one.

So after searching on OSO and finding that guys said this AIRTEX 90632 worked I have to say that its not TRUE. I looked it up and it only has 1/4 inch threaded lines in and out. I have 3/8ths. What pump do I need? The old one is a carter 0-2208? This is driving me nuts.

CV products makes a complete pump.. SPIN-MP-2600

Or use a Mercruiser or Airtex top half and change out the bottom half with a CV products one or a KE...

http://www.cpperformance.com/p-12460...6-engines.aspx



I used a CV Bottom half I got used from a Winston cup team... Looks like the part number is cv5505-2
http://i130.photobucket.com/albums/p...e/P1030827.jpg

Is that a steady 7.5 PSI at sustained full throttle? Pressure at idle or even cruise doesn't tell you much. You need to know if you are starving it for fuel while under sustained load. You might have to crack the hatch and have someone keep an eye on it. Or you can do what I did and mount a GoPro camera aimed at the gauge, if you don't have a remote gauge.

Thank you for the good idea. I am going to toss in my gopro and put the old crap back in for a fast test run. Since I am three miles from the ramp a quick spin will reveal all. Fuel pressure and see if the pump seals are weeping.

You can download an app for your smartphone which will allow you to use your phone as a remote monitor and start / stop recording. :cool:

Or use some of that extra -whatever hose you have and move the gauge?

What RPM's did it turn originally, and what prop were you running? Are you running the same prop? Why did you stop the dyno before you found peak power? I believe you should prop your boat for peak HP. ( where the engine wants to run) By over propping and loading the engine you are more prone to detonation. And a 6000+HP 502 you should be spinning close to 6000RPM. What heads did you use and cam now? The boat is the only true dyno.

1/4"npt vs 3/8" hard line, also the number is 60932. It does infact work, bolts right in...I own one.

One thing we never talk about because I don't think anyone has checked, I'm suprised I haven't either, is since the sea water/fuel pump is belt/pulley driven, what it is driven vs crank speed.

A regular block mounted pump is 1/2 engine speed because of being driven off a cam lobe.

If the sea wwater pump is driven faster than 1/2 crank speed, we'll get more pumping action.

Anyone wanna measure crank pulley diam and sea water pump diameter to come up with fp driven speed ?

Interesting point, SB. I would assume that there is a limit to how fast you can operate these pumps. Otherwise you would get issues with the arm floating on the cam. However, not having a heavy pushrod to move the arm probably helps. So I guess the moral of the story may be that you can still get the job done with a smaller pump - you just have to pump faster! :lolhit:

lol !!!!!!!!!!!

Say you have a normal pushrod set up good to 8k rpm. Remember 1/2 crank speed. Fuel pump is at 4kstrokes per minute.

Sea Water pump: Say 6000rpm engine, .659 x crank speed = 4k strokes per minute. No pushrod for fuel pump. Should be safe for non floating.

Anyway, if you look at a mech fuel pump flow graph, rpm is everything for max volume.

what pump do they use on the bravo raw water pump? i hear it isn't a 454 block mount pump.

What about fuel line size? What is the smallest choke point size?