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james_lloyd
07-09-2008, 01:36 PM
Hi,
Before i brought my 1994 prostar 190 the EFI was taken off and the engine had a carb put back on. Apparently this was something to do with the boat being put on to LPG.
Anyway my boats top speed is 50kph and will not go any faster. I am sure that it should be going faster.
Could this be due to the efi being taken off?
is there anything i can do to try and increase the top speed?
I am wanting to barefoot behind my prostar and cannot do it at this speed.

Thanks!!:confused:

shunra
07-09-2008, 01:52 PM
The speedometer is likely in mph not kph. Are you sure you are only going 50kph? If so what are you RPMs at when at top speed? You might need a different prop. Are you still running LPG?

james_lloyd
07-09-2008, 01:57 PM
Hi, It is definately KPH and it tops out at around 3000 rpm. i got a 13inch 4 blade prop on it and the boat is on dual fuel. Doesn't matter if you run it on lpg or petrol it will only reach 50kph. Have tried a different prop and gained an extra 4kph.

Thanks

BrianM
07-09-2008, 02:04 PM
You should be able to turn about 4800 rpm with that motor. You have some sort of a problem. Someone around here ought to be able to give you some advise on what to check.

NU-skier
07-09-2008, 02:06 PM
Verify that the throttle cable is able to open the carb all the way to the stop.

Muttley
07-09-2008, 02:11 PM
50 kph = 30 mph. You should be doing over 70 kph (45 mph)

I don't think that too many people on this side of the pond have much experience with propane, but on my old truck the difference was nominal. The carb itself should not make a difference over the EFI, but it could be something to do the propane calibration. I know there were some vehicles that had an issue with the jets freezing.

Perhaps a propane expert will chime in.

james_lloyd
07-09-2008, 02:26 PM
The throttle cable does open the carb all the way to the stop.
It does run fine on both petrol and lpg but like i say on both fuels it will top out at 50kph.
there are some linkages on the one side of the carb that do look slightly dodgy! these linkages are to the two top flaps on the carb. Not sure what sort of carb is on mine. Will take a photo and put it on the thread so you can see for yourselves.

Thanks again:confused:

rob935
07-09-2008, 03:52 PM
i would check the throttle cable for sure as it sounds like the carb isnt being opened up fully ...

rob935
07-09-2008, 03:55 PM
you probably have a holley 4160 , another possibility would be that the secondary part of the carb isnt opening up and this is what would give you the extra grunt and rpms at the higher throttle end ....

james_lloyd
07-09-2008, 04:02 PM
Have checked the flap on the carb for the throttle cable and that is definately opening fully. The secondary flap i am not so sure of. will have a look and try ang get some photo's of it on also.
Have seen some photo's of a holley 4160 carb but not sure if it looks the same as mine.
Thanks for the advice guys!

GuitsBoy
07-10-2008, 08:42 AM
Carb??? I thought it was a GM based 5.7 with EFI (throttle body injection???)

6ballsisall
07-10-2008, 08:53 AM
Have you taken a look at the ignition components? I.E. Distributor cap, rotor, wires, plugs, coil, etc.....

east tx skier
07-10-2008, 11:05 AM
Carb??? I thought it was a GM based 5.7 with EFI (throttle body injection???)

His post says EFI was swapped to carb for LPG conversion.

GuitsBoy
07-10-2008, 11:16 AM
His post says EFI was swapped to carb for LPG conversion.

WOW, how in the world did my eyeballs miss that. Sorry bout that.

james_lloyd
07-10-2008, 01:04 PM
Yes have checked all the usual things - plugs leads points etc. It does seem like a carb problem though as it just gets to that speed and just stops going any faster so does seem like the second flaps not functioning correctly. Will have a good look at the weekend.

Thanks

randyb
07-10-2008, 04:54 PM
Have you called someone at either Acme or OJ props to verify that what you have on there will allow the motor to get up to top rpm's?

Jim@BAWS
07-10-2008, 05:29 PM
Not a PROP problem

FUEL delivery problem

Consult your local MC dealer accross the pond
He should have some working knowledge of this

Jim@BAWS