what gives?

[oilfieldtrash]

I'm guessing the 700 had some issues the 850 doesn't have. The motor wouldn't run like shit with the 700, it might lay down a little around 6500 if it were truly starving for fuel. The 850 seems to run better because the extra fuel is crutching the motor, simular to a manual choke on a Chevy 6 while cruising at low RPMs......As mentioned, alot can be said for ignition timing, camshaft location, compression ratio, etc etc etc......Again, IMO, 850 is too much fuel for a 460 turning under 5K.............However, IF the 850 makes the boat drivable, and you're having fun, go for it, enjoy..........MP
thanks man i am goin to have to take another look at the 700. i guess i am going to have to find a better combo to go with i just figured that i would see more out of the combo i put together this winter. anybody have any ideas or a recipe for a good combo that will build good power and turn some r's. please help im really disappointed with my present situation.

[gbelt]

How old is the distributor? Does it have a solid 12v source? I know when I've done that swap in a car I always use a 10 gauge wire to feed it because they draw a lot of power, if you have something smaller it may have worked with your old setup since you were only running 4300 or so, maybe it needs a little more. Are the contacts on the module and those conecting to the coil clean? Any wobble to the shaft? Stock modules seem to be good for about 5000-5500 rpm, if you had a spare I'd throw that in and give it a try. Me personally would try bumping the timing to 34 or 36, clean off all the connections that have to do with the ignition, just remember to check the plugs because I doubt you'd hear any detonation with the OT pipes.

[oilfieldtrash]

How old is the distributor? Does it have a solid 12v source? I know when I've done that swap in a car I always use a 10 gauge wire to feed it because they draw a lot of power, if you have something smaller it may have worked with your old setup since you were only running 4300 or so, maybe it needs a little more. Are the contacts on the module and those conecting to the coil clean? Any wobble to the shaft? Stock modules seem to be good for about 5000-5500 rpm, if you had a spare I'd throw that in and give it a try. Me personally would try bumping the timing to 34 or 36, clean off all the connections that have to do with the ignition, just remember to check the plugs because I doubt you'd hear any detonation with the OT pipes.
cool thanks for the info. i was thinking about buying a new msd or dui distributor. the one that is in the boat is old and it is a car one any suggustions on a new one?

[gbelt]

You can buy a brand new Mallory HEI from Summit for about 150, it's not a marine unit but then again neither is the one you have now. I have a Unilite in my boat, it's been reliable, only had to replace the module once in 15 years and that was because of a bad ground, but to be honest I'd rather have the HEI just to clean up the wiring. A good thing about the HEI is you can get parts for them reasonably priced just about anywhere, I'd have to hunt to find the Unilite rotor that my distributor takes (so I carry a spare). You can't go wrong with MSD, I don't have any experience with DUI systems. For the price that Mallory is going to be hard to beat since it's complete with coil. Good luck, your combination looks sound and reliable, probably just needs a bit of tweaking on the spark and fuel to get some more out of it.

[squirt]

What size impeller are you turnning and what pump??????? There is no way to know if 4500rpm is a good number for your motor without knowing just how much load is on the motor. It could be ok for a AA, not so good for an A, and piss poor for a B. Also make sure your tach reads right. I'd bump the timming like suggested to 34-36 deg. It takes about 340 hp to spin a good A impeller to 4700 and it looks like you have a little more cam than a stocker. Somethig is not right here.
Don

[oilfieldtrash]

What size impeller are you turnning and what pump??????? There is no way to know if 4500rpm is a good number for your motor without knowing just how much load is on the motor. It could be ok for a AA, not so good for an A, and piss poor for a B. Also make sure your tach reads right. I'd bump the timming like suggested to 34-36 deg. It takes about 340 hp to spin a good A impeller to 4700 and it looks like you have a little more cam than a stocker. Somethig is not right here.
Don
i have a berk 12JG with an A impeller. the cam is not huge but it is bigger than stock. i will try bumping up the timing and see what happens. would rebuilding the pump and installing a place divertor help the situation?
thanks for the info. o-ya how would cheak the tach to make sure it is reading right?
casey

[BrendellaJet]

i have a berk 12JG with an A impeller. the cam is not huge but it is bigger than stock. i will try bumping up the timing and see what happens. would rebuilding the pump and installing a place divertor help the situation?
thanks for the info. o-ya how would cheak the tach to make sure it is reading right?
casey
Might want to talk to some of the resident desktop dyno gurus and see if we can get an estimate on the power you are making. Jet pumps take horsepower to turn. FYI, guys running jetboat specific motors with 700 hp turn their pumps in the6000-6200 range, that gives you an idea of how hard they are to turn...
If you want more speed, gotta make more power. Rebuilding the pump will probably lower RPMs some, but may produce more speed. Definitely go with a place diverter if you dont already have one, They are great for trimming your boat and are fun to play with too.

[squirt]

i have a berk 12JG with an A impeller. the cam is not huge but it is bigger than stock. i will try bumping up the timing and see what happens. would rebuilding the pump and installing a place divertor help the situation?
thanks for the info. o-ya how would cheak the tach to make sure it is reading right?
casey
No rebuilding a pump usually tightens things up and will decrease rpm further but if ya need a rebuild ya need one. A place diverter is a good thing but won't effect how your engine spins the pump. RPMs are low for a BBC and that impeller I would think 4800-4900 would be closer, even if you were running 8-1 flat tops and closed chambers. You can check the tach with a know source, a verified tach/ dwell meter, an old dist machine for curving dists., a MSD ign tester, or a speedo shop. Did you check to see that the secondaries are opening all the way at WOT on that carb?????

[oilfieldtrash]

Might want to talk to some of the resident desktop dyno gurus and see if we can get an estimate on the power you are making. Jet pumps take horsepower to turn. FYI, guys running jetboat specific motors with 700 hp turn their pumps in the6000-6200 range, that gives you an idea of how hard they are to turn...
If you want more speed, gotta make more power. Rebuilding the pump will probably lower RPMs some, but may produce more speed. Definitely go with a place diverter if you dont already have one, They are great for trimming your boat and are fun to play with too.
who on here is handy with the desktop dyno? how much hp does it take to turn an A impeller to 4500-4600 rpm?

[oilfieldtrash]

No rebuilding a pump usually tightens things up and will decrease rpm further but if ya need a rebuild ya need one. A place diverter is a good thing but won't effect how your engine spins the pump. RPMs are low for a BBC and that impeller I would think 4800-4900 would be closer, even if you were running 8-1 flat tops and closed chambers. You can check the tach with a know source, a verified tach/ dwell meter, an old dist machine for curving dists., a MSD ign tester, or a speedo shop. Did you check to see that the secondaries are opening all the way at WOT on that carb?????
ya i know if i rebuild the pump it will make it more efficant and harder to turn more power needed iam going to order a new distributor and check the tach i figured i would make 400 - 450 horse with set up i am running. is that out of the question?