Cant get RPM out of a 454, 330hp
 

I been trying to tackle my problem of no rpm for the season. I am stumped and don't no where to look anymore. It is a 87 330hp 454, just over 400 hrs. Brand new heads last season, due to one being cracked. I read a few dif. ways online to set the flat tappet valves which i did myself. I was wondering if this could be causing my problem? Few mechanics say it runs way to smooth to be a valve problem. Also spinning a 19 pitch prop, which i should be turning a 21!

So far.....

Checked timing, base is 10* advancing to 35*
compression is 120psi all cyl
new fuel pump
checks anti siphon in tank
Made sure secondaries are opening
had dean nickerson rebuild my carb this season.

I don't no where else to check or what to do? I give the boat gas and it jumps to 3500ish till i plane off and then i hammer it and i will get 3800. Thats it. Runs smooth, no back fires, no weird noise just like it has a 3800rpm limit. I am lost. Any ideas would be greatly appreciated!

Need much more info for anyone to help you.

How big of boat, what kind, how much does it weigh.

What kind of heads. Did you change anything else.

120 compression should be around 150 on each cylinder.

1987 maybe the old girl is tired.:drink:

You said you lost RPM, but did you lose speed? Maybe your tach is messed up??

120 compression is good, would not cause RPM loss.

Have you check wide open throttle, make sure when you are wide that the carb linkage is wide open also. to start with

sorry guys,

boat is a formula 223 ls. Weight is right on, also weighed it thinking foam was water logged or something. Its a BBC alpha.

It has been this way since i owned the boat. I noticed water in oil after driving it one time and ended up being a cracked head. I replaced it with the small oval port head that was stock, stupid i know! Didn't no much about boats when i did it 3 years ago. I have had 2 tachs on it, just upgraded my dash this season. I am getting 53 mph gps @ 3800rpm. Also checked the linkage, opening all the way.

i was also thinking tired motor but people i have talked to also same 120psi i should still be getting rpm and it only has 400 hrs on it. Very clean and unabused boat. Thanks again for helping guys!

Will it free rev? without a load on it and in nuetral. Has it ever gone past this RPM? If not, could be prop pitch.

yes i can rev it fine when not under a load. like i said i am spinning a 19 pitch. It should do that with ease no? I have seen a few other 223 owners spinning 21s!

There outdrive gear ratio could be different than yours. If you don't know their gear ratio vs yours, you can't compare prop pitch.

Yeah, I'm starting to think someone swapped your alpha with one of a different ratio because they didn't know any better. While 3800rpm isn't enough for that motor, 53mph is not far off for that boat/power, especially if it's not quite optimized.

My 223 turns a 22p B1, but at 3800 I'm running middle 40s on the speedo. It will just tickle 60 on a good day, ~4600 rpm.

At this point the easiest thing to do might to be try and and find a 17p prop and test that theory.