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View Full Version : '96 Classic 22 w/ 454 21p quicksilver prop 4100rpm?



sub-bass
02-19-2007, 09:36 PM
I have a '96 Classic 22 30th Anniversary Edition w/ 454, Bravo 1, Mirage 21P prop, Rochester carb and running NO airfilter on 98 Octane Shell fuel with straight through exhaust. Only done 100 odd hours. all filters have been changed.
My question is - This set up seems to give me around 63 - 65 mph (not GPS tested) and will only give me a max of 4100 rpm (sometimes 4200 rpm). Does this seems awefully low for the prop/leg/engine configuration or do I have serious problems?
It feels quick and not sluggish down low but I'm surprised at the 4200rpm max, it even stutters a little right up top. Leads? rev limiter? or other?
Any advise would be appreciated on this..
ta
Sub-bass

MOP
02-20-2007, 06:32 AM
There are a few things that could be stealing power for starters get rid of the 98 and run 89, higher octane does -0- unless you have the mods to to benefit from it. A compression check then on to fuel filters, fresh ignition wires & plugs are always good and make sure the timing is correct at idle and at higher rpm.

Phil

Pismo
02-20-2007, 07:18 AM
You should be getting near 65mph GPS top speed. Get a GPS to verify speed. Run the 98 octane down to empty then fill with 89. I agree, plugs, wires, rotor, distributor cap, timing, make sure timing advance is working, watch it advance with a light as you rev. With your carb you can easily tell if you are running out of fuel at any speed. Have someone press down the accelerator pump post sticking straight up from the front corner of the carb. It should feel smooth and firm like it is squirting fuel and it may temporarily flood the engine, if it feels easy or irregular like it is pumping air then you have a fuel flow problem. If so, check the stand pipe in the fuel tank for a clog or the fuel pump pressure. Compression test. Look for water in the oil. Its a 7.4L, not a 454 Mag so no 70mph.

Sofa King
02-20-2007, 08:32 AM
Trim out your drive and your tabs and watch the rpms go, I used to have the same problem:yes:

RedDog
02-20-2007, 09:46 AM
I wonder if you are running the 1.36:1 drive ration vs. the more common 1.5:1? Most of the 22 Classics have the 1.5 and spin a 23 to 25 inch prop to the 5000 RPM range. If you have the 1.5 drive, then spinning a 21 inch prop should result in pegging the tach

maddad
02-20-2007, 10:02 AM
Is the tach set for a 6 cyl. and the breakup at WOT is the motor bumping the rev limit?

sub-bass
02-20-2007, 08:54 PM
Hi folks, many many thanks for all of the helpful input and tech advise. I'll be in the water tomorrow with new fuel and hopefully my mechanic friend to implement some of the suggestions. My old man (Dad) has a few props from previous boats.

Once again thank you to all and I welcome further suggestions.


Sub-bass

sub-bass
02-20-2007, 09:09 PM
Is the tach set for a 6 cyl. and the breakup at WOT is the motor bumping the rev limit?


As far as I'm aware the tach set is the original that came with the the boat, how would I adjust the rev-limit or isn't this possible?

oldandtired
02-23-2007, 06:25 PM
Something is fishy with your numbers. 4100 rpm with a 21 pitch prop yields 54 mph with a 1.5 and 60 mph with a 1.36. Those are theoretical speeds (no slip). Your real speed will be 9-15% less. I think your tach may be wrong or your speedo is wrong. Of course, you should check the engine out and make sure that it gets running right. If you have the 330 hp 454, 62-64 mph is probably a good speed for the entire package. Maybe you are on the limiter, but are getting a bad tach reading. Get a portable tach and check your tach out first.

Rene

PS The tach and the rev limiter are independent of each other. The limiter is in the computer. It can be adjusted by reprogramming, but you have no reason to do it on a stock engine. The good news to this is that it sounds like you need some more prop and will see higher top speeds.

sub-bass
02-24-2007, 11:12 PM
OK, the numbers may be a little fishy I agree as the speed was an estimate gauged by another boats Speedo - RPM indication should be ok but we'll run some tests after the timing gets checked and new plugs/leads happen this week (boat sat for some 3-4 years in a dry warehouse).
Does anyone think it's a problem to run this 7.4 lt (with Power steer and came with the new '96 boat) which is stock standard in a rev-range above 4200 rpm for any length of time or is it something that should be persued after modifications only - I'm talking a flat-run up a river for 50-60 miles. And should I look into a prop that is maybe 23p and up??
If I can identify this engine for you more specifically then please let me know how I can indicate that to you.
Also, where is the computer in this boat please?

Many thanks

Sub-bass

oldandtired
02-26-2007, 11:56 AM
I am not 100% certain, but I'm pretty sure that the 7.4's were 330 hp, 454's. I'm pretty sure that the designation was a 7.4lx. The rpm range should be around 4600-4800 max. there is no reason to be worried about running it anywhere in the normal range. The computer should be in the electrical box with the red button on the port side of the engine. I am assuming that it's fuel injected.

Rene