Runs Great Out Just Not In Water

[capt.murph]

Newbie Jetter Please Help!!! Runs Good Out Of Water On Garden Hose.idles Good In Water But When U Hit The Throtle It Screams To 4000 Rpm Then Falls On It Face.455 Olds&berkley Pump. Good Compresion New Cap& Distr.plugs Wires,fuel Pumpany Other Advice For Process Ofelimanation(sorrygot Long Winded)thanks In Advance

[El Prosecutor]

Newbie Jetter Please Help!!! Runs Good Out Of Water On Garden Hose.idles Good In Water But When U Hit The Throtle It Screams To 4000 Rpm Then Falls On It Face.455 Olds&berkley Pump. Good Compresion New Cap& Distr.plugs Wires,fuel Pumpany Other Advice For Process Ofelimanation(sorrygot Long Winded)thanks In Advance
I am pretty new at this too, but wanted to offer a couple friendly thoughts.
First off, I have a 455 Olds in my boat and thought I'd warn you about oiling problems in the 455. Seems that oil moves up faster than it flows down in the Olds, so if you run it at WOT longer than a minute or two it will pump all the oil into the valve covers and out the breather. Pumped a quart out the breather myself about a month ago. Fortunately I shut it down before anything got ruined.
I am not sure what you meant by "falls on its face" - do you mean that the RPM drops suddenly, RPM stays the same but the boat stops accelerating, RPM hits a ceiling at 4000, or what? Jet Drives will limit the RPM of the engine based on the impeller size. Larger impeller = lower max RPM, which IMHO is a good thing if you are running an Olds.
Anyway, I am sure if you give some more details on the problem you will get some informed opinions on what the problem is.
I would also suggest using the search tool to search the forums for "Olds Oiling Problems" and "Impeller size comparison". There is also some great Olds specific info at www.realoldspower.com
Good luck with your problem - summer is just about here!

[poncho-pwr]

We need more information by what you mean when you said "it falls on it's face". Do you mean that once the boat is off the trailer and in the water running that it will rev up to 4000rpm when you hit the throttle and then drop way back down and not turn as many rpm? And for God's sake as well as your own PLEASE quit running your jetboat out of the water. Even with the garden hose hooked up you are killing your pump, it is not designed to be run out of the water and sticking a hose up in the jet pump isn't going to help much. A lot of first time jet boat owners (myself included) don't or didn't know you aren't supposed to run them on the trailer out of the water because you see so many people doing it, so don't feel bad just don't do it again.

[centerhill condor]

poncho is right about the don't run the pump without water... usually, when an engine races to a certain power level and can't do any more fuel shortage is the problem... my boat tops out at 4200 rpm @ 55 mph indicated ( non gps)... depending on your impeller (wheel) you may be at the max! best of luck!

[Knucklehead]

Out of the water it's not under a load correct, In the water it is...

[1975sleekcraft]

when your boat is on the trailer you cant get on it for long. when it's in the water you can hit 4000 for more than a second.your running out of gas .check your float levels-fuel pump pressure-etc.

[Devilman]

Sounds like it may be running out of fuel? Friend of mine bought a boat with a freshly rebuilt 455. It would start, idle, & rev up fine. But, when he would take off, just about the time it would get on plane, it would die. Did this several times getting back to the ramp. Turned out to be the electric fuel pump the previous owner had installed. It was some cheesy little universal-type & basically couldn't keep up. Took it off & put a factory type manual pump back on the motor & it ran its ass off the rest of the weekend. :cool:
This being said not knowing what kind of fuel pump you have.... :rollside:

[toad polumsky]

Thats what my boat does. It turns 8000 rpm on the trailer, and as soon as it gets in the lake it only turns 5250 rpm. We must have the same problem going on.

[Legal Chemistry]

Maybe this will help. My car will do 0-60 in < 2 seconds up on jack stands.... but will "only" do it in 6 seconds on the streets. So with resistance from the water you can only move that size impeller so fast w/x HP. Damn Toad, I have the same problem too!

[toad polumsky]

So what are you saying? That I have to take jackstands to the lake with me.

[Legal Chemistry]

You don't bring your jackstands with you to the lake? I keep my boat strapped to the trailer w/jackstands connected. Extra 500 rpm's every time -keeps the boat out of the water more. lol

[capt.murph]

when i say falls on its face i mean it will take off and just about as itwould get on plane it will die.starts right back up.put new mechanical pump on and checked fuel pressure it was good.played with the timing too. PULLED MOTOR TODAY (PREVIOUS OWNER POORLY INSTALEED)A DRAIN VALVE IN OIL PAN TO MAKE CHANGING OIL EASIER&CLEANER. CAME LOSE THOUGH AND WATER GOT IN SIDE PAN DIDNT NOTICE TILL CHECKING OIL BEFORE PRE LAUNCH .TOOK PAN DOWN (LESS THAN A QUART OF MILKY OIL) CAM APPEARS TO HAVE LIGHT BLUE TINT(LACK OF OIL).PULLED ONE CAM BEARING LOOKED FINE. FIND OUT MORE TOMMORROW . (P.S WONT RUN PUMP OUT OF WATER BETTER TO BE SAFE THAN SORRY)thanks alot for the advice will keep everyone posted on my luck

[speed freak]

Had simular problem with my boat. Pick ups in both tanks gummed up over the winter. Ran fine until the carb bowls ran out of fuel.

[twowheeledfish]

Had simular problem with my boat. Pick ups in both tanks gummed up over the winter. Ran fine until the carb bowls ran out of fuel.
This is along the same lines I was thinking. A buddy and I just fixed a centurion with the same problem. The carb was brand new, but evidently the fuel filter/water separator does not filter small particles from the fuel and the inlet screen in the carb where the fuel line enters was plugged with fine sediment. Both screens on the fuel bowl needles were plugged too. The boat had sat for awhile and sucked some junk from the tank when first started. We cleaned everything out and it ran fine. For certain you are draining your bowls and it is causing the engine to fall flat. Could also be a collapsing old fuel line, fuel pump, etc.