SoCal Jet Boats
Tech Talk => Jet Pumps => Topic started by: YumaJet on May 12, 2009, 09:57:51 AM
-
I finally took out my gps this weekend and It "only" went up to 50mph @ 4200rpm. I could only imagine my pump is hurting for a rebuild. It has a "A" impeller, split bowl (12jb) with diverter. Whats the average price to pay for a pump rebuild? I'm sure it will need a few upgrades to hit 60plus mph. The pump sounds good, so I don't know why it doesn't want to squuze out a few more mph's. The motor is a fesh 454 bbc. topics are worthless without pics, so here are a few.
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi270.photobucket.com%2Falbums%2Fjj114%2Fro69rag%2Fuse1.jpg&hash=23ba407d6c21e936ef4f9da8e465c5d305085e5a)
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi270.photobucket.com%2Falbums%2Fjj114%2Fro69rag%2Fuse2.jpg&hash=bc9adde75bde61455d6b9494bf649f4d5cad5d09)
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi270.photobucket.com%2Falbums%2Fjj114%2Fro69rag%2Fuse3.jpg&hash=8400646f13bddd3705319eac81c82ebe48f696bb)
-
Hey Yuma
you can give Tom at JBP a call. i believe he has the rebuild kits. you can also get the rebuild kits from Berkeley. cant remember teh price from berkeley but you can find on their website.
good luck on the rebuild.
oh yeah look up JBP on here to get Tom`s number or he might even jump on here with it.
-
Here's Tom's number 805-466-4718 (My blackberry might have them mixed up, but if this is your personal number Tom, forgive me)
Doubt if the pumps the problem though. I'm not an expert, but sounds to me like you're either have too much impeller or not enough motor. Topping out at 4200 rpm is NOT ideal for a jet boat as I understand the charts and curves. 5000 rpm seems to be the baseline for max impeller effectiveness. More speed, smaller impeller, makes sense, BUT, much more HP involved to turn that impeller at speed. It's not as simple as adding 50 HP and dropping from a "B" to an "A". The "A" impeller takes more HP than most advertised engine hp make to make it work properly . The engine HP needs to be aimed specifically at 5000 rpm. That's quite a bit different than a street or drag engine. Tom will chime in and correct me on this if I'm way off base, but that's my understanding of it.
It's an exponential computation that I think not many of us (Me included), other than Crewcheif, could not get a handle on anyway. Use the charts and be realistic, not optimistic, about your estimated HP.
I have a similar problem in my cruiser, and am working on changing out the intake, carb and ignition to grab a few more horsies and rpm as I beleive that is the problem. Probably gonna get more involved such as a cam, springs, etc. This winter the cruiser may see a new engine geared for what it should be.
Just my .02
Ray
-
sounds like your pump is loading...otherwise more rpms and less mph...my boat only turns 4300 no gps number but probably not far off from your speed...i see you got all them there wedgies for a cool guy roost...from my understanding that can hurt your rpm and mph...there is so many factors that can play and someone much smarter then me will chime in on this...i see you are running a stock rock grate what about trying a loader?
-
Call desert yacht in yuma and ask for vic. Couldent hurt to at least call since he is in the same city as you!
Desert Yacht Performance Marine
3191 W 5th St, Yuma, AZ 85364-2638
Contact Phone: (928) 783-9441
URL (web address):
Business Category: Repair Services in Yuma, AZ
I have a lot of friends who drive all the way from san diego to get work done by him.
-
are you sure you didnt pick up the only 2 rocks in yuma?
wait, sorry, someone else already did ;D
-
are you sure you didnt pick up the only 2 rocks in yuma?
wait, sorry, someone else already did ;D
That's funny shit right there!!
-
Ditch the wedges. Or better yet, ditch one of them and put the other in so it wedges down (fat side up) Get a good loader and make sure your impeller isn't all chewed up. Good luck.
-
Albert One thing I see is that your Step/trim tabs are likley "fighting you boat speed " With 4200 rpms (assumably an "A"?) your down on power a little and thats likely a "tune" issue (should be closer to 4800 assumingg your tachs correct) at this point any aggressive loader beyond a rock grate is going to aggravate your issues IMO Call me later and I"ll roll thru this with you Tom
-
4200 with an "A" is about 300 hp +/-. Without any details on your 454, that can be very realistic - not a problem with your pump, but you need more power. Check and see your secondaries are opening all the way (if vacuum you need to do this under load on the water not in your driveway). I was stuck at 4200 b/c my secondaries did not open. Once fixed WOT was shy of 5k.
You need to pull your impeller out to see what size it is... you can't tell by looks.
-
4200 with an "A" is about 300 hp +/-. Without any details on your 454, that can be very realistic - not a problem with your pump, but you need more power. Check and see your secondaries are opening all the way (if vacuum you need to do this under load on the water not in your driveway). I was stuck at 4200 b/c my secondaries did not open. Once fixed WOT was shy of 5k.
You need to pull your impeller out to see what size it is... you can't tell by looks.
FWIW a stock 454 without any major work makes 330-350 HP right out of the box.
Also FWIW, you do not have to "pull" the impeller, but rather the bowl (which is only a couple steps short of pulling the impeller) to check is size (betting an A). simple verbal clarification, no offense intended ;) That being said, I agree that the carburetor is a good starting point. If you don't already have one, go pick up a cheapie vacuum gauge. :sly:
Totally agree on removing or cancelling out the wedge. I would also be careful puting that much strain on the steering cable attatchment bolt and tiller arm, as it sits you need a swivel... 8)
Assuming that pump has never been apart, there has been a lot of sand/gravel passed through that badboy looking at the condition of the intake. :-\
IMHO you need to verify your RPM's with a trustworthy tach, then get the most HP possible tuned into your motor and go from there...Have you looked up through the grate at the impeller?
You may see something obvious....
A loader at this point would be a step backward if your info. is correct (like Tom says).
Another little "tid bit" that is sometimes overlooked, have you had the boat/trailer weighed? Sometimes these old boats get water logged and we don't even know it......Just sayin'.
One more thing, I find it odd that we put on some Step and Trim's, but have the nozzle wedged like a MOFO O0, I think someone was trying to make a NHRA roost, on a SCCA budget ::)
(meaning nothing more than they cancel each other out).
Good luck!
GT
-
Thanks for all of the replies. Here are a few motor specs:
1. Blueprinted and Balanced Motor (Bored .60 over and balanced within 2 grams)
2. Two-Bolt Main with Steel Crank
3. MSD Ignition (Distributor, 6A Box, Coil,Wires)
4. Edelbrock Air-Gap Intake (w/ 1” Spacer)
5. Holley 750cfm Carburetor
6. Flat Top Pistons (8:1 comp)
7. Comp Cams Mild 280 Cam
8. Comp Cams True Roller Rockers with Rail Kit
9. Steel I-Beam Rods with cc's push rods
10. Eight Quart “Hamburger” Oil Pan
11. High Volume Oil Pump
12. Uses 20w50 Valvoline Racing Motor Oil
13. Holley 7-9psi Mechanical Fuel Pump
14. Comp Cams Double Roller Timing Chain
15. GM heads (ported and polished)
I do not use a vacuum on my carb, and have often thought since the carb has never been rebuilt, it could be plugged up alittle. I've known Vic for a good 17 years and has a new full time mechanic job at bp that limits him alittle on working on jet boats. He was going to charge me a grip just for labor to work on the pump ($700 plus.) My motor should be pushing an honest 400-450hp. In no way, does my motor sound strained when it hits 4300, so im sure the pump is loading up. I used a digital rpm reader when I maxed out the rpm's, so the rpms are true and correct. I cleaned out the bowl and intake.
The wedges give me the "cool points." Yet, I know, you can have speed or a cool rooster. I didnt have the the gps when I had to wedge, so i dont know if the wedges effect it much. Common sense, says they would effect it alittle. I have never taken off a pump or grate, but am handy with the tools.
I figured I was going to find a good hull with pump before summer, but have't found the "right one" yet, so this hull has been it so far.
-
GT, no offense taken. Thanks for the clarification.
-
Help me out on this,,, you guys usually do! In my mind the worse the pump
condition the higher the engine rpms will be.
True or false?
If true he needs a Ford engine for that doggie ;D
-
Help me out on this,,, you guys usually do! In my mind the worse the pump
condition the higher the engine rpms will be.
True or false?
If true he needs a Ford engine for that doggie ;D
that's my understanding. a tight pump will turn less than a loose one.
-
Help me out on this,,, you guys usually do! In my mind the worse the pump
condition the higher the engine rpms will be.
True or false?
If true he needs a Ford engine for that doggie ;D
Unless it has a 15# Booger in it :-* ;D
GT
-
A properly built , clearanced , installed ,and operating jet (mixed flow) will act like a "water dyno" and limit your (assumably good running engine) to its actual horse power. The "impeller charts are seldom wrong" Althought "they" (worn and damaged jets) will work ,they usually exibit higher than normal RPMs vs speed . .... goin' to the lake!
Yuma the only thing I might question (later when time) is the cam vs the compression ratio , I'll research when time permits
HYDRAULIC-Jet boat with A impeller. Skiing Hyd. Hyd. 2400 to 6400 11-314-4 280AH 280 288 232 237 .547 .547 110°
and pleasure use, good performance.