SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: drogers87 on August 14, 2016, 07:48:04 AM
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Hi guys,
New to motors here (first boat, learning all the in's and outs). Just got back from a week on the water at lake Powell, what an awesome place. Ran the boat all week and ran well except a flutter and occasional pop at high rpm.
1982 Carrera 20.5
454 BBC
High performance heads
All stock to my knowledge beyond that
Anyone had a similar problem with a flutter and/or popping at high rpm? Whether I was coming out of the hole or on plane fls
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Fuel pressure?
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...The flutter stayed the same. (sorry baby grabbed phone and created post too soon!).
Thought maybe it was a valve sticking but I just had the valves done... Worn cam loab? Lifter?
I thought I was an air/fuel problem at first but messed with the carb, distributor, boat sounds great from idle to 4300/4500 rpm... I'm stumped. Any thoughts, troubleshooting ideas, suggestions are appreciated. Any help is appreciated!
- Dan
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floating the valves possibly, ignition issue xould be anything
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Fuel valve? Sucking air at higher rpms? O rings in fuel valve?
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Kona - havnt checked pressure yet. Simple as putting in an inline gauge at the fuel rain?
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You can do that ... Is it manual or electronic fuel pump?
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I should have stated... This was happening before I had the valves done and I thought it would take care of the problem...
In talking with a guy who said he had a similar problem, he had a cam lobe wear and wasn't opening completely. Possibility?
Sounds like I need to go back in the heads 😡
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Manual pump
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I'll be at Riviera weekend after next 8/26-28 if anyone is there and wants to hear for themselves. Just throwing it out there
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Kona - manual and brand new as well
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Kona - manual and brand new as well
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I would still check fuel pressure and volume
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Should there be a vacuum attached the carb? Power valve? It's a holly 750 marine carb. Disconnected the secondaries and it didn't solve anything. If the power valve isn't opening could it be in line with a fuel volume/ pressure issue at high rpm? There is a vacuum port on carb with a rubber cap on it under the secondary side... ???
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...The flutter stayed the same. (sorry baby grabbed phone and created post too soon!).
Thought maybe it was a valve sticking but I just had the valves done... Worn cam loab? Lifter?
I thought I was an air/fuel problem at first but messed with the carb, distributor, boat sounds great from idle to 4300/4500 rpm... I'm stumped. Any thoughts, troubleshooting ideas, suggestions are appreciated. Any help is appreciated!
- Dan
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Where do you hear the popping?
How was the valve guide clearance set up?
Fuel pressure?
What is the spark plug gap and distributor cap condition?
GT
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Should there be a vacuum attached the carb? Power valve? It's a holly 750 marine carb. Disconnected the secondaries and it didn't solve anything. If the power valve isn't opening could it be in line with a fuel volume/ pressure issue at high rpm? There is a vacuum port on carb with a rubber cap on it under the secondary side... ???
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Why are you saying power valve? Do you suspect an issue? Only reason I ask is that it is a total possibility.
If you do replace it, don't put back in a 6.5, drop it down to about a 5 or 5.5.
Has it always done this?
You said high performance heads, what do you mean by that?
Is the tach stable when it shits itself?
Does it have a Rev limiter?
What ignition?
GT
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I suggested the powe valve because I noticed a vacuum line was not connected. My understanding that it works off of vacuum...? I did disconnect secondaries and had the same problem.
Only had the boat for 2 months and always had this problem.
Didn't see the heads, just told by the motor guy it has larger ports...
Electronic ignition
New plugs and wires within the last 6 months.
GT - the number of the power valve correlate to the amount of fuel passing through? Lower number - less fuel?
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I suggested the powe valve because I noticed a vacuum line was not connected. My understanding that it works off of vacuum...? I did disconnect secondaries and had the same problem.
Only had the boat for 2 months and always had this problem.
Didn't see the heads, just told by the motor guy it has larger ports...
Electronic ignition
New plugs and wires within the last 6 months.
GT - the number of the power valve correlate to the amount of fuel passing through? Lower number - less fuel?
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Don't worry about the plugged vacuum port it would be for a vacuum advance if it were a car.
As for the power valve, the number notes the vacuum level the valve begins to open. So it would open starring at the number on the valve in inches mercury vacuum.
By dropping the number it keeps it out of the picture until later in the rpm range, allowing you to tune the mid range more effectively.
The power valve is in the primaries btw.
GT
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Thanks for the helps guys, I really appreciate it. You all are awesome, I have some work to do.
Thanks
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GT - could wire gauge be a factor? Wires were replaced before I bought the boat and seems the guy I bought it from made some Mickey Mouse repairs. Just wondering if he hooked up the wrong size wire...? Just a thought, I'll have to look at the wires closer and figure out what is on there versus what should be on there
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Well, being as you weren't too specific.
Voltage drop is the most detrimental thing in a boat. Voltage drop causes increased amp draw and heat.
If the voltage going to the ignition coil is allowed to get too low, it could certainly cause what you describe.
You could probably check it with a volt meter or by using a jumper wire at the coil to the battery at the engine.
In answer to your question, totally, undersized wire or a sketchy splice can cause all sorts of goofy stuff to happen.
GT
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Awesome thank you, I think that is where I'm going to start. Much appreciated GT!
Thanks all, I'll let you know what happens.
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Too add to what GT states. What ignition system do you have. What is your timing at. What is your total advance. Sounds like the same thing that happened to me when I had a fresh motor I built (N/A) and put an MSD pro billet in. I would accel like and animal but at a certain RPM like around 4000 if I rememeber it would sputter and spit. I could however drive through it. I was not reading the MSD instructions correctly for the colored eccetrics as well as the springs. It hit me right before I fell asleep one nite. I had it fixed the next day by changing the color of the eccentric. I had way too much advance in it (like 44 degrees all in at 3800rpms). I think I bought it down to 36 total all in at 3400RPM or something like that. I threw this all out the window when I went blown EFI back then.
Hope this helps.
T.J.
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Just to wrap this up for all that helped:
Ran the boat out of Mcntyre weekend before last and ZERO issues with flutter at high rpm. Ran the boat to about 5000-5100rpm and sounded clean and smooth.
Looking back at the chain of events, at the end of the Powell trip 3 weeks ago I had (what I thought) ran out of fuel on the water. Actually had fuel just only drew from one tank. Between the Powell trip and Mcntyre I pulled out fuel pickups and noticed I had a check valve in the side that wasn't drawing. All I can guess is that check valve was limiting the fuel flow (and then finally quit working at Powell) and I wasn't getting enough fuel to the motor. I wish I had paid more attention to the different levels of fuel when filling the boat. Looking back I remember putting more fuel in the one side... 😁🔨
Drilled out the valve and removed spring, reassembled pickups and ran great at the river. Still havnt put a fuel pressure gauge on the line but I bet it is where it should be now! Just glad I don't have to go back into motor looking for a ghost...
Thanks again all the help, had I given that info from my first post this probably wouldn't have been such a big deal. Thanks!
Dan
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I'm going to say this and I want you to know that this is not an attack, just an awareness and a warning so bad things don't happen.
Drawing off both tanks simultaneously is silly. Absolutely no reason to do so.
That being said, you know what that valve was for?
It's called an anti siphon valve. The reason it's there is to prevent the draining of the tank in the chance that you have a fuel leak below the fuel level in the tank. This could be anything from a cracked fuel fitting, bad hose, failed fuel pump, anything. Those check valves in my opinion, need to be in there. What I would recommend is replacing both tank siphon valves with new brass ones (don't waste your time with the aluminum) and buy two, full port ball valves and install them on the tee. Run both valves open if you want, but throttle the "fast" tank. This way, when you are running low on fuel, you can ensure getting back to the beach. You just shut the empty tanks valve.
Do you have dual level senders?
There was a burned boat just the other day that someone had video of, that right there is reason enough to do it right (not to mention legal).
You nearly blew up the engine running lean if the previous information isn't enough.
Be safe and have fun, you can do both at the same time. Trust me.
GT
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Thanks for the advice, I wasn't sure what the valves purpose was (possibly to keep the line primed...?) now I know. Being safe is fun and now that you explained it I will get new valves installed. That little girl in the picture I posted is priority #1.
Hypothetically speaking, if I still have problems not drawing enough fuel through the check valves, is it as easy as upsizing the pump or going electric? Running a basic gm manual pump currently.
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Thanks for the advice, I wasn't sure what the valves purpose was (possibly to keep the line primed...?) now I know. Being safe is fun and now that you explained it I will get new valves installed. That little girl in the picture I posted is priority #1.
Hypothetically speaking, if I still have problems not drawing enough fuel through the check valves, is it as easy as upsizing the pump or going electric? Running a basic gm manual pump currently.
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It shouldn't be a GM pump, to my knowledge they never manufactured a marine accepted pump, it's likely either a Carter marine mechanical or similar, most of these mechanical pumps can support in excess of 600+ hp with little or no drama.
You have a closed engine, meaning every single thing on the engine should be USCG approved with an SAE Marine spec number.
You could always upgrade all the fuel lines to 1/2", but it shouldn't be necessary.
Beautiful daughter BTW.
JMO
GT
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It is a brand new fuel pump at that. When I ran out of fuel on the water I switched my tank selector over and couldnt pull fuel through the valve... Sound like a bad valve to you? I imagine they have a lifespan on them.
The boat sat for some time between the previous owner and when I bought it...? Just a thought
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It is a brand new fuel pump at that. When I ran out of fuel on the water I switched my tank selector over and couldnt pull fuel through the valve... Sound like a bad valve to you? I imagine they have a lifespan on them.
The boat sat for some time between the previous owner and when I bought it...? Just a thought
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Which valve? A black plastic deal?
If so, toss it. Lol
GT.
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Ok I will do some research and look a little closer. I love having my boat garaged but hate that it is 30miles away!
I appreciate the help and yes she is beautiful. First child... She's not spoiled I swear...
Dan
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Chrome box tank selector. Brass anti-syphon valve. Wasn't a ball, spring and "piston" design.
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Ok I will do some research and look a little closer. I love having my boat garaged but hate that it is 30miles away!
I appreciate the help and yes she is beautiful. First child... She's not spoiled I swear...
Dan
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Lol, you won't know how spoiled until you have a second. My "little girl" just graduated UC Santa Cruz.
Sure miss them when they grow up.