Lack of power

[mchas3]

I have a 24' Commander Supercruiser with a bone stock 454 and Bravo 1 outdrive. My problem is that is has dramatically lost speed over the years. Originally a 60 mph boat, I'm now lucky to get it up to 54 mph. I've had to prop down to a Merc 19 Revolution 4 blade prop just to get it out of the hold for skiing and to get RPM's back up to 4400. Any suggestions to bring back some performance without breaking the bank. I'll be happy just to get the boat back up to the low 60's mph range.

[Maverick]

[QUOTE]Originally posted by mchas3:
[B]I have a 24' Commander
If you leave the boat in the water, I would guess that you have "taken on water" and the hull (strigers etc.) are water saturated -- now everthing is heavy. Also, check the bottom of your hull. Have you developed a "hook"? This can critically deminish speed.
If you have any kind of high speed "miss", I would suggest you check for an exhaust lobe going down on you cam.
Also, check your spark advance at WOT. The "box" that advances timing have been known to fail. This is probably the easiest to check. You should show around 8deg. at idle and around 34deg at WOT.
If you are missing 4 degrees or so at WOT, you will see a big difference in performance. Some people say with good gas you can run 38deg @ WOT, others seem to think you can "detonate" your motor above 34deg. Be you own judge!!
let me know if we hit the mark here.
More knowledge never a bad thing....
MAverick

[Maverick]

[QUOTE]Originally posted by mchas3:
[B]I have a 24' Commander
If you leave the boat in the water, I would guess that you have "taken on water" and the hull (strigers etc.) are water saturated -- now everthing is heavy. Also, check the bottom of your hull. Have you developed a "hook"? This can critically deminish speed.
If you have any kind of high speed "miss", I would suggest you check for an exhaust lobe going down on you cam.
Also, check your spark advance at WOT. The "box" that advances timing have been known to fail. This is probably the easiest to check. You should show around 8deg. at idle and around 34deg at WOT.
If you are missing 4 degrees or so at WOT, you will see a big difference in performance. Some people say with good gas you can run 38deg @ WOT, others seem to think you can "detonate" your motor above 34deg. Be you own judge!!
The other possibility is a loss of compression in one of your cylinders ( could be a cam going down, could be a burned valve, could be a broken or worn piston ring). A simple compression check on all eight cylingers will tell the tale. None of these are "good things" -- certainly not an easy fix.
Let me know if we hit the mark here.
More knowledge never a bad thing....
MAverick

[Bondo]

hi, i think MAverick has it pretty well summed up, you don't mention how many hours in all those "years"..... it might be time to bite the bullet + rebuild....depending on how much you can,or will do yourself, your looking at $1500./$2000./+, to make that a "little better than new" motor...
even on a trailer, if stored outdoors, it could be a lot "heavier", And have a hook, than when new...
I think?

[mchas3]

The boat is kept on a trailer outdoors but covered. Until the last two years it mainly has been kept at Lake Havasu, AZ. Total hours on the boat is 475. It is a sound hull but that doesn't mean it hasn't absorbed some moisture over the years. I'm open to any suggestions on improvement if it does turn out to be a rebuild. What should the compression be? At last check, it was about 135 - 145 across the board.

[Bondo]

i guess where i was heading was; at some point all the "Little things" start to add up, the little dishes in the bottom of flat lifters get a little deeper, the cam doesn't lift quite as high as it did, the valves are sitting a little deeper in the seats, the pistons are wobbling just a Little bit,......just the valve,lifter, cam Could affect the dynamic compression ratio Alot...openning later,+ closing sooner....deppending on "Who" owned the engine, i've seen motors wear in 500hrs or less... then others that pull strong at 1000hrs..
I think?

[Maverick]

[QUOTE]Originally posted by mchas3:
[B]The boat is kept on a trailer outdoors but covered.
Your compression @ 135 lbs is getting a little "soft". If the motor is run - then checked -- you should get your best reading.
If you want to take the next step, check a cylinder, then squirt a little oil in the cylinder and recheck - if the compression comes up - rings are the issue.
I'm being nosy now ---- what kind of oil have you been running in that motor?? I'll bet NOT "Mobil 1".
Maverick
[This message has been edited by Maverick (edited March 20, 2002).]