SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: 1978southwind on April 21, 2011, 08:15:38 PM
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OK so first off i am new here and currently a new boat owner of a 1978 southwind jet. I just built a 460 and put it in the boat an it runs great except the fact that it wont run over 3,500 Rpms. Now im not expert but im sure a 460 big block in a boat should run higher than that right ??? I have a 460 preformer manifold with a holly double pumper carb. mallory distributor with MSD coil. The guy that i bought the engine block from told me to run a tourqer manifiold and i didnt cause at the time i was just trying to save money. So if you guys could give me any hints to as what i am doing wrong or doing everything wrong just call me a dumb ass i am fine with it i am new to this so work with me here :o either reply back on here or email or text me 805-453-4217 i would be verythank full for all the advice i could get
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Welcome to SCJB ;D
First thing I would recommend is try a different tach. The original tach in my boat was way off.
If you're still getting the same rpm range you need to look deeper into the engine build and/or combination of parts.
Giving us some more details about the build will help us determine if there is something wrong or just a small problem (cam numbers, pistons, approximate compression ratio, cylinder head numbers, carb size...).
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What GPS speeds are you running at 3500? What is the engine doing at 3500? Cutting out? Shutting off? Or is that all she's got?
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Crewchief: off the top of my head i can tell you carb size i think is a 730. The heads I think are just stock, ill check on the rest today.
Brendella: It wont gove over 3,500 and its acts like thats all shes got but whats werid is when i have the boat out of the water just running on a hose ill rev out to 5,000 rpms easy so i dont know whats going on
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Check pump for duct tape....
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sounds like you are down on power! had the same issue with my bbf...would only rev out to 4200 or some shit like that! Your impeller is holding the motor back...It could be possible that your pump has an aa impeller or something
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HDriderTH: The pump in the jet?
Nordie: i dont know what is in it. its a berkeley jet not sure what kind of impeller is that something i could find out if i called manufacture. If it is a aa impeller what new impeller would you recogmend. An should i put the tourker manifold on?
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What is you timing set at? And do you have a different carb you could try?
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i think im set at 10 ? i would have to ask my friend who timed the engine for me. um sadly no i dont have a diff carb. You think its to big for that engine ? i think im going to have to get a better manifold to work with the carb and the rest of the engine. My engine builder told me to get the tourker to run on the boat but i didnt have the money at the time nowim starting to think i should just get it.
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I'd recommend checking the timing while running in the water to see what the total advance is. You should be around 34-36 degrees total.
Verify that you are getting full throttle. The engine will free rev on the trailer with a lot less effort than it will under load.
A mild build should be able to pull into the 4000-4500rpm range without much trouble. It's that last 1000-1500rpm that starts to cost a lot of money ;)
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All the things you mention help the engine to run more effeciently, however you need parts to make more HP, such as heads,cam comp ratio etc. Again not being familuar with jet pumps and what HP they demand, I would say as you explain your motor I would say you are closer to 300-325 hp .
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Check pump for duct tape....
HDriderTH: The pump in the jet?
Some people call the the whole assembly a pump because it's a water pump more than a true jet.
Look up into the intake area from the bottom of the boat for debris. Rocks and junk can (and will) get sucked up inside and cause loss of thrust and sometimes vibrations.
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Thank you all for the advice. crewchief i will take a look in the pump because i was just at lake san antonio and there was stuff floating everywhere.
Should i be looking into bigger heads anyone?
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Ford casting numbers are visible on the outside of the cylinder heads (will be something like D0VE-A...).
Post the casting numbers and one of the Ford guys will give some opinions about what you have.
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Ford casting numbers are visible on the outside of the cylinder heads (will be something like D0VE-A...).
Post the casting numbers and one of the Ford guys will give some opinions about what you have.
exactly were on the heads are they located
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Heads.....Irrelevant.
Carb.....Irrelevant.
Manifold....Irrelevant.
Impeller cut....Irrelevant (to an extent).
Need to knows; Ignition timing at 2500+ RPM, actual tach reading at a confirmed (with a dwell/tach meter) 2500 RPM, fuel pressure at 2500+RPM under load, throttle blade position at WOT (engine not running), Compression check on all cylinders (not looking for a specific number, just consistency), firing order (don't laugh, they will actually run pretty good with the wrong order)...
These are all free to check if you or someone you know knows how. :thumbup:
I would be willing to bet it will be something silly, IMHO if it does not run to at least 4300-4500 RPM it will be something fairly obvious. Even if the boat weighs 10,000 pounds you should be able to see that RPM.
GT
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I'm no expert on here like the rest of these guys, but I had the exact same issue but mine wouldn't go over 3200. I was running a vacuum advance distributer and my secondaries were never opening due to not enough vacuum, basically it was starving for fuel and running like a 2barrel.
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exactly were on the heads are they located
Casting #s are on the exhaust side of the head over the #2 and #7 cylinder exhaust ports (just below the valve cover rail).
Can you contact the builder and get a part# for the cam he put in it ? Thats what everyone is going to ask for next. ;)
Like GT posted, check to make sure you are actually getting full throttle at the carb (primary and secondary sides are fully open at full throttle). Check timing at 2500+ rpm. Something screwy is going on here, even if theres a AA impeller in that pump. 3500rpm with an AA impeller is only right around 160hp. Even a stock truck motor should do better than that. :sly:
Check pump for duct tape....
::)
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All good suggestions are waranteed, however you would be most benifited to be sure the engine you have is runing the best it can. That would be correct timing, all vacumn accesories are working properly, dist and carb. Correct jets in carb. I would run a single wire HEI dist simple, work well.
When all that is correct than you can advance to different heads, manifold,exhaust, bore size etc. All the accesories you mention don't amount to more hp only to help in obtaining the above. When the engine is runing the best then what it has to push,turn pull will come into play. EX. disconnect all compentents and turn the engine to any rpm you want, hook it up its a different story. Everything componet on or hooked to the engine is relevent to its performance.