can't plane or maybe another issue.

[Familyman1981]

i have an inboard ski boat with a 454 engine it feels as i have no power. the tach at full throttle is roughly 3200 but it will not "get up and go" im not sure if maybe my propeller is improper for my boat or maybe the engine is not adjusted properly does 3200 rpm sound right for such a big motor? anyways super new to owning a boat i dont have any friends or family who own or have owned a boat to ask. so i'm hoping the collective wisdom of the community can help give me some ideas to help me enjoy my boat with my family. oh and should there be a neutral on my boat because when i have the boat in what should be neutral the propeller still turns slightly.

 

[Familyman1981]

Re: can't plane or maybe another issue.

oh and another thing when i have the throttle fully open i get a backfire from the carb and ideas what that means?

 

[Bondo]

Re: can't plane or maybe another issue.

Ayuh,.... Wecome Aboard,...
It sounds like the motor is atleast runnin' lean, by the backfires at throttlin' it...

Without Any history, I'd think a general Tune Up, 'n Service is in order,...
Throw in a Compression Test, just to find out the general Health of the motor...

I'd think you should be seein' around 4600/ 4800rpms at Wot...

 

[RobbyA]

Re: can't plane or maybe another issue.

I'd think you should be seein' around 4600/ 4800rpms at Wot...

On a big block? Of course I don't know, but in the auto world if you see that on a stock 454 for any length of time, I think you would see 4600/ 4800 pieces flying off the motor.

 

[waterinthefuel]

Re: can't plane or maybe another issue.

On a big block? Of course I don't know, but in the auto world if you see that on a stock 454 for any length of time, I think you would see 4600/ 4800 pieces flying off the motor.

Didn't we already decide that a 454 in a car and in a boat are two separate engines with separate purposes thus comparing performance numbers on them was futile?

 

[RobbyA]

Re: can't plane or maybe another issue.

Didn't we already decide that a 454 in a car and in a boat are two separate engines with separate purposes thus comparing performance numbers on them was futile?

That's why I said I didn't know.

but a quick google search showed me this:
454 MAG MPI Specifications


Propshaft Horsepower: 385 (287 kw)
Displacement (Liter/CID): 7.4/454
Cylinders: V-8
Bore (in/mm): 4.25/108
Stroke (in/mm): 4.00/102
Compression Ratio: 8.6:1
Fuel Requirements: 87 Posted Octane (R+M)/2
Full Throttle RPM Range: 4600-5000
Ignition Type: Digital
Alternator: 65/917
Length (in/cm): 39/991
Width (in/cm): 32/813
Height (in/cm): 22/559
Weight (lbs/kg): 1177/534 (Weight with Bravo One Drive)

all I can say is WOW!

 

[KC4YIN]

Re: can't plane or maybe another issue.

The little 3 liter Mercruiser135 I had would turn up 4800 WOT all the time. One day I saw it hit 5000 going with the wind. Course we did not run WOT all the time, but yes that big block 454 should turn more than what it is now.
I'd start with a compression test and or tune up.

 

[JetBote]

Re: can't plane or maybe another issue.

Make sure the secondaries are opening.

 

[JetBote]

Re: can't plane or maybe another issue.

On a big block? Of course I don't know, but in the auto world if you see that on a stock 454 for any length of time, I think you would see 4600/ 4800 pieces flying off the motor.

You're kidding, right?

 

[Familyman1981]

Re: can't plane or maybe another issue.

Secondaries?

 

[RobbyA]

Re: can't plane or maybe another issue.

You're kidding, right?

No I wasn't kidding. My friend had a late 90's 3/4 ton Chevy that red lined at about that and it sounded like it was red lining!!!!! I am a import man where 5000 rpm is just getting started. I pull my boat with a 1/2 Chevy Suburban and I know if it ever saw 5k rpm I would be parking it on the side of the road, especially if it saw that for any length of time. I never realized there is that much difference between marine motors and auto motors. I was always told as a kid i/o were the devil and to stay away from them so I truly don't know. I guess thats why I have only owned outboards

 

[Sharp Shooter]

Re: can't plane or maybe another issue.

No I wasn't kidding. My friend had a late 90's 3/4 ton Chevy that red lined at about that and it sounded like it was red lining!!!!! I am a import man where 5000 rpm is just getting started. I pull my boat with a 1/2 Chevy Suburban and I know if it ever saw 5k rpm I would be parking it on the side of the road, especially if it saw that for any length of time. I never realized there is that much difference between marine motors and auto motors. I was always told as a kid i/o were the devil and to stay away from them so I truly don't know. I guess thats why I have only owned outboards

Don't assume all 454 engines are the same. For example, a 1970 454 in a chevelle will make a lot more power and rev much higher than your friends small port low compression truck engine....

 

[spudshaft]

Re: can't plane or maybe another issue.

Yep. You're rpm's are low. I think the previous poster is thinking of a diesel or something. 454's are tough motors

 

[Sharp Shooter]

Re: can't plane or maybe another issue.

i have an inboard ski boat with a 454 engine it feels as i have no power. the tach at full throttle is roughly 3200 but it will not "get up and go" im not sure if maybe my propeller is improper for my boat or maybe the engine is not adjusted properly does 3200 rpm sound right for such a big motor? anyways super new to owning a boat i dont have any friends or family who own or have owned a boat to ask. so i'm hoping the collective wisdom of the community can help give me some ideas to help me enjoy my boat with my family. oh and should there be a neutral on my boat because when i have the boat in what should be neutral the propeller still turns slightly.

Your engine should rev in the neighborhood 4,500 to 4,800 if it's original and in good working order.

I would start with engine timing based on the back firing. And the fact that the engine needs to be timed at all is a possible indicator that all your settings may be off. Unless you possess basic mechanical ability I would suggest taking it to a good mechanic. Most automotive shops can take care of tuning your 454.

 

[Sharp Shooter]

Re: can't plane or maybe another issue.

Didn't we already decide that a 454 in a car and in a boat are two separate engines with separate purposes thus comparing performance numbers on them was futile?

The GM 454 is an automotive based engine that can be configured to accomodate a wide range of usage.

With any engine, the reciprocating assembly, compression ratio, cylinder heads, camshaft choice, fuel system, ignition and exhaust all play a role in engine performance.

There are a number of aftermarket and factory parts available to build anything from a late model low emission 454 to full blown race engine (still 454 if desired) that can rev 8,500+ rpm.

An engine builder utilizes the necessary parts needed to achieve the performance goals that are set for the finished product.

The difference between a car and boat 454 may differ greatly. I know of many boats running engines they plucked right out of a car or truck only adding their marine parts such as engine mounts water pump and exhaust changes.

 

[JetBote]

Re: can't plane or maybe another issue.

Secondaries?

Take off the flame arrestor (air cleaner) and tell us how many holes you can see. 2, or 4? Being a 5L, you may only have a two barrel carb. If 4, the front two are primaries, the back two are secondaries. They open when fuel and air demand exceed the output of the primaries.

 

[eastont]

Re: can't plane or maybe another issue.

Get a compression test before anything else, Backfiring through the carb sounds like intake valves................

Been there and done that

 

[DuckHunterJon]

Re: can't plane or maybe another issue.

I think the backfiring through the carb has to be dealt with before power issues - and will most likely point toward/fix the power issues.

To backfire through the carb, either your timing is off (getting spark while intake valves are open = low power), or you have a stuck valve/valves (again, would severely limit the power). You can check the valves with a leak down or compression test (I prefer leak down tests as they can show more than the compression test - think longer duration). If that passes, check timing.

Only other thing I've seen cause backfiring through carb is severe carbon build up on pistons. Carbon heats up red hot, and pre ignites airfuel mixture (this is often accompanied with "deiseling" - engine continues to run, albiet rough, when you shut it down). Fix for this is start it up, get it warmed up, bring the rpms up a bit, and slowly dump water directly into the carb until motor stalls out. Sounds scarry, but it is basically rapidly cooling the carbon deposits, and they flake off. Think of it as steam cleaning the piston/cyl/heads.

Good luck with it and let us know what you find.

 

[gbeltran]

Re: can't plane or maybe another issue.

Take off the flame arrestor (air cleaner) and tell us how many holes you can see. 2, or 4? Being a 5L, you may only have a two barrel carb. If 4, the front two are primaries, the back two are secondaries. They open when fuel and air demand exceed the output of the primaries.

5L? A 454 is 7.4, it will definitely have a 4 barrel carburetor.

 

[Familyman1981]

Re: can't plane or maybe another issue.

its a 4 barrel holley carb. I will have to get the timing checked because i dont have a timing gun to adjust or check the timing. so as soon as i know i'll post an update thanks everyone for helping to point me in the right direction.

OH.... and when the gear shift is in neutral should the prop be spinning?