wont reach WOT

[coolair]

Happy thanksgiving to everyone!
I am looking for ideas as to the cause of my problem. The boat is back in the water, shafts aligned and everything running great at the dock. Not so much when we put a load on her. I can not get either engine to go above 37/3800RPM and when you try and push them they actually start to fall off.
From idle to 32/3400 RPM run great.
Ford 460 big blocks with aftermarket EFI systems. both motors do the identical thing.

First thought is fuel, but my fuel pressure does not drop off, it actually goes up based on the vacuum.

[scenarioL113]

What was your RPM the last time all was working properly? What RPM should you be getting?

Has anything changed since then? Weight wise, Prop wise?

Are you getting your speed? knots/mph...did you change the tachometers? or Alternators or something that may be affecting the tach signal

Both engines are performing the same so my gut tells me they may be OK so something possibly in the props or added weight or drag.

Gives us more of a rundown of what was done when she was out of the water


Happy Thanksgiving

[Tony Meola]

Matt

Sounds almost like it is a fuel/air mixture issue. Props not set right would just make you top off, RPMs would not drop. Maybe the fuel filters need to be bigger, or perhaps the fuel lines are not sized right. Or it could just be the EFI system not running right.

Hopefully Bruce will have an idea for you.

[Bruce]

It sounds like your using a vacuum controlled fuel pressure regulator. What's the regulator set at?
Are you throttle body or mpi injection. If mpi, what lb injectors are you running?

What size fuel lines are you running and are you running a return to the tank or recirculating system.

Does the efi control timing, or are you base static with a mechanical advance?

Have you popped some plugs to check them. Most aftermarket efi are learn type, most run rich to prevent lean and damage and easy foul plugs till they learn especially if they don't have an O2 sensor. Do you have Air/fuel ratio guage?.

[MikeD@Lightningshack]

My 454 used to do this occasionally and usually late in the season. She had carbs and the carbs had screens where the fuel enters. For some reason they would get plugged with a plaque like film, never figured out why. You could barely see it because it was the same color as the mesh. I'd clean or replace them and she'd be fine.

Sure sounds like it is being starved of fuel, especially because it is happening on both engines. The question is why and where. I'd check all filters, separators and any screen or strainers between the tank and Injectors.

Good luck,
Mike

[coolair]

The weather has been bad last few days so I have not had a chance to get updated and exact numbers.

Previously I was getting close to 4500rpm, I honestly don't remember exactly. But I dont think the weight has changed drastically. I did add a generator and more electronics, but the deck is now composite which weighs less. My props have not changed.
I was sorta thinking it could be props, but I dont think enough has changed in weight and horsepower that would effect the props.

I have about a half tank of fuel right now. I was making 24.5 knots around 3000 to 3200 rpm.

I am running FAST EFI which uses one O2 sensor and is a throttle body system. It does Not control timing. It has a hand held controller that tells you air/fuel ratio among many other things.

Fuel lines are 3/8" id and I have a return line that comes out of the regulator and goes back to the tank.

I have racor fuel filters between the engine and the fuel pump. I am not sure what size they are. I do know they are 1/4"npt fittings though.
But probably wouldn't hurt to go a head and change them.

The regulator does work off of a vacuum, and it is set at around 43PSI per the manufactures recommendations.

I have not pulled any plugs yet.

Timing is static plus mechanical advance, which I am thinking is part of my problem. I am using a MSD ready to run distributor.

I have the timing set to 5°btdc based on what the Chrysler service manual says(though these are fords they were marinized by Chrysler originally) and the MSD distributor is set up to provide 21° of advance. Which would give me a total of 26°

NOW based on the Ford service manual my timing should be at 10°btdc and I would have a total of 31°
what I have been reading on other forums they are setting the 460s around 12 to 14 base timing and shooting for 36° total timing.

But is that timing issue a enough to cause the engine to loose power or not produce full power.

[MikeD@Lightningshack]

Are the fuel valves at tank accessible and verified to be fully open?

The drop off makes me think it is not timing, as I would expect lower power but I would not expect the power to fall off if it was a pure timing issue. The fact that it is falling off still sounds like fuel starvation.

[scenarioL113]

Just for troubleshooting purposes you need
To see what your “all in” timing is and what rpm it is when it gets there.
This may not be a timing issue but timing being correct is extremely important for Power and fuel economy.

Lets say the timing was a bit off but was close, now you add a little weight (generator) and it is just at that point now where she just isnt creating enough power to get that top end.

Its possible and ez to check. You can ck timing at the dock.

Let us know

[scenarioL113]

According to your post regarding timing you need to play with timing advance for your engine. Sounds like you do not have enough advance.

100% not enough timing will def give you less power.
It will not cause it to drop off tho.

When weather is better you can just play with the advance and drive the boat. Just leave hold down bolt loose enough that you can still turn the distributor and move it amlottle at a time and see how it effects the performance.

An aftermarket distributor may react differently than the oem one and dialing it in may see better results.

Like i said get timing correct first then troubleshoot other areas. Thats what i would do

[Carl]

Read the plugs.

1/4" fittings sound too small, plenty of fuel when loafing along but push the throttles forward and your lines are being sucked dry starving motor of fuel loosing power.

Also check the flow rating of your fuel filters.
Make sure fuel valves completely open
Intake screen is not clogged
Vent screen is not clogged


I saw it once and that was enough to keep me from running my ol 440's hard. Yes flowscans show the gph...at least till I pegged them when 4 barrels kicked in. Yes, I read what 440' are rated to burn at WOT. Yes, I know what the fuel bill was when I hit the fuel dock after a hard run.
What I did not expect to see and left a lasting impression on me is when I was having an problem and mechanic had me go out and run the motors to the pins with an open carb. What you need to understand is I drive standing on my motor box, which for him to see was removed so I was standing on the motor looking straight down the carb barrels...

I was used to seeing fuel being sprayed in...once I got motor to the pins it looked like a garden hose at full blast, that was my holy sh$t moment that I see every time I pushed those motors. I guess I'm exaggerating about garden hose full blast, but it's the impression I got.

Anyway, 460's have to be thirsty creatures and I'm thinking fuel starvation.


If not getting full power, I'd say timing, but you said drops off.


Or it could be the EFI, but when talking about that I am out of my element and why I choose not to answer earlier.

Super quick way to try if it's fuel restriction....big hoses into jerry jugs to the fuel pumps. Boat goes full bore or it don't.


I think this is where the warnings about running from a jerry jug come into play.

[Tooeez]

Are these the same engines you had before? It's a real longshot, but a restriction in the exhaust will produce exactly what you describe; normal operation until the motor can't breathe anymore, than an even reduction the more the throttle is opened. If the new engines have more displacement or breathe more efficiently they may have pushed your exhaust system to its limit. You can check with a vacuum gauge--if the reading starts to fall as the rpm's drop off it means no more air can go through the carb because it can't get out the other end.

[coolair]

The fuel filters I have worked when I was running carbs, I think they are rated at 60GPH but I am going to verify that tomorrow as well as everything else.

Same engines. but new exhaust manifolds, risers. WHICH I am alittle worried that the exhaust is part of the problem. I was very limited on my exhaust options as the 460 is not very popular and at the time I was being cheap, the money canon was running low on ammo and I was in a hurry so I didnt want to order the high dollar racing stuff and didnt want to wait for the custom copper manifolds. The riser does start out at 3" which maybe alittle small, but then goes to the original 4" exhaust.

[coolair]

Timing seems to have helped alot. We are still falling short of 4500RPM and still having it fall off a bit. but we made it to 4200RPM on the tach doing 30knots burning 49gph. I have one size smaller bushing I can put in the distributor to advance the timing a little bit further, which I probably will do.

On the EFI computer the most I got was 4050 RPM. Not sure which is off, the tach or EFI computer.

at 4050 I had a load of 98% and a AF ratio of 12.8 and a target of 12.8 and a 41% duty cycle on the injectors.

I think those numbers are in the realm of need the props adjusted...

[scenarioL113]

Just so you know if you are not sure, you can check timing at the dock in neutral to see how much advance you are getting. The engine does NOT need to be under load.

You can also set it to where you want to and just make sure when the engine is hot that you can still start it without the starter laboring to turn her over which would be a symptom of too much advance.

Great news tho and this may be one of a few minor probs that are contributing to this issue.

[Carl]

The 98% load tells me you should be looking at props.

Provided the rest of you drive train is right on...alignment, shafts turn free, no vibration.