Well u probly have the same nasty fiberglass tanks as the other Halletts
I'm getting new tanks as we speak ordering new aluminum ones from imco
I changed all lines to larger fuel selector and have two filters didn't help
Mine would bog every once in a while shit hitting the pick up the tiny pickup
How did the fuel system look before u cleaned it I had to look into my tank in the garage with a maglite to see the crap inside

How old is the pump and wear ring

If its worn out its like driving a car with a slipping tranny

Is the tach correct?
51 mph @ 2900 doesn't add up

Daniel

I had the same problem last summer, turns out i somehow had 2 plug wires in the wrong position. it wouldn't get above 3000 rpms but idled good and ran good. a buddy of mine rechecked the plug wires and found it. after that it ran better than ever!

I had the same problem last summer, turns out i somehow had 2 plug wires in the wrong position. it wouldn't get above 3000 rpms but idled good and ran good. a buddy of mine rechecked the plug wires and found it. after that it ran better than ever!

That's actually one I wouldn't have thought of right off the bat, but does kinda fit.

I'm also in agreement with Daniel that 51 MPH at 2900 RPM is an incredible crazy number!! Tachometer HAS to be jacked up, IMHO. Hearing it run, does it SOUND like 2900 RPM? 2900 RPM is a bit over what most cars cruise at, at say, 75MPH, on the freeway.

Ray

Do the secondaries open

Are they mech or vacuum

Just making sure u rechecked the fuel and fire

Msd with proper coil.  Its not 180 out

What Carb is it is it a new huge arb with stock tiny fuel lines

I'm a Chevy guy but even a blue oval will spin more than that stock

It's a holley 750, possibly an 850, mostly stock motor.  Secondaries open and they are vac. MSD R2R with a blaster SS coil, no balast resistor.  I doubt it is 180 out because it doesn't run bad at all, sounds really good actually.  I'm gonna check fire order in the morning.  I have 3/8" fuel line, it goes:

Tank pick ups to manual selector valve
Selector valve to fuel/water separator (1 week old)
Separator to mech fuel pump with new filter inside

I need to replace the fuel lines from tanks to the selector which I will do tomorrow, have new Gates reinforced fuel injection lines already. Coworker suggested if the lines are old or not the right quality they can suck themselves shut and restrict flow, and that is why all boats have upgraded fuel lines from automotive applications.  I won't be able to get it on the water again until sunday though.

If it was 180* out you would know it. A couple plug wires in the wrong place, that's one I wouldn't have thought of, but worth a check. Seen that on U-Haul trucks in the past.

I'm going with the concensus that the tach is snafu. Or it's incompatible/not set up correctly with your ignition, something. 51 MPH out of a pretty heavy 19' Hallett does not equate to 2900 rpm on a stock 320 HP engine. Just not buying into that.

Also, on the hose, remember you are not loading the motor. A Jet Drive, IN the water, acts, for the most part, the same way a dynamometer does to measure crankshaft HP. The jet drive, for the most part. (I know, some of us are hitting them with 6-7-800 HP and a few well beyond that, but that is an entirely different matter). The motor is gonna quit before the jet drive does, if the jet is in decent shape. More RPM, more resistance to the engine at an exponential rate. This is why you can almost look at a Berkeley Impeller chart and find your impeller, and your max RPM, and be pretty darn close to what a dyno would tell you your max HP is AT that RPM.

A standard, marine 460 is a 320 HP deal, and usually an A impeller in the pump SHOULD let you spin up to 4600 or so RPM. My old 21' Biesemeyer had a fairly fresh, new, Harmin Marine 460 and JC-A and would spin to 48-4900 with no problem. A whopping 50 MPH.........Mind you....... Only mod was an 800 CFM carb.

I'm not saying your boat is as heavy as that old tank was, but if you're pulling 51 MPH at 2900 basically stock, we are ALL doing something WRONG!

Running the boat on the hose, you are only trying to cool the motor, and hopefully you're stuffing a hose both up the intake and up the wazoo to lubricate the pump while doing this! What is going to happen doing that is the motor is free-wheeling and will spin up to whichever gives up first, the ignition or the valvesprings.  Means nothing about where the power is, or where the problem may lie. Particularly with a Vac Sec'y carb (Which I am in the minority of being a fan of). 

Keep these things in mind playing with this thing. 

Ray

I was just trying to keep it simple

Even if the tach was wrong ur GPS should show u some more speed.  Tach wrong or not not ur issue keep on the fire and fuel path till u know neither one are wrong

Same ignition just different Carb before???

55 with a loaded boat probly not too far off there

Why did u change carbs

Although I had a 20 foot Tahiti minday and had a stock 454 iron manifold and all only thing I had was a 750dp and loaded down 4 peeps icechest ski ropes jackets anchor she ran 56 on GPS and that thing had a Panther jet.

Even bone stock u should be mid 50

His Hallett I would liken to my Charger. VERY heavy, well laid up boat! I can almost taste 60, consistently (It's done 67 downriver......with a tailwind.......) with my Charger now that it has an energized YJ, Diverter with a mild 455. But that is a lot of pump work to make that happen.

In Vegas's case, he has a pump/engine combo rebuilt maybe, what, 30 years ago?

No, 51 is a very respectable number, and enjoyable! Obviously, some tired hardware there, IMHO.

The "non-working tach" comment caught my eye though. Is this the SAME tach?

Ray

Check the back of tach to make sure it is set on 8 clyinders not 4 or 6 cylinders. if its not missing or anything the motor, could be that tach.

Sorry what I meant was keep looking if the motor is done revving at 3000 grand watchingtach or not if it runs flat while u have throttle left sounds funny.