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winner21

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ok guy's i have a 96 4.3 i

ok guy's i have a 96 4.3 in a 21' boat. at wot i can only get 3800 out of it at 28 mph im runing a 15 pitch prop what do u guy's think the prob is
eny help would be great.
 
"Ok, if you can give us a bit

"Ok, if you can give us a bit more info I can probably suggest some areas to check.
1) Is this how it's always been or has it previously run higher wot revs which for a 4.3 should be more like 4500 or so?
2) Boat model or weight and beam?
3) Drive ratio?

Mike"
 
this 4.3 has ran like this sin

this 4.3 has ran like this since i put it in it's used came out of a 96 regal. the other 4.3 that was in my boat ran at 4500. the boat is a 21' winner cuddy cabin weight dry is 3800.the drive ratio is 1.84.1 somthin like that.
 
did that 178 on all moter runs

did that 178 on all moter runs great but just cant get her past 3800 under load and the moter is burning alot of fuel.
 
"I used 4500 lbs. as a loaded

"I used 4500 lbs. as a loaded weight, 175 hp, @ sea level = 17P prop. SS prop will give best performance. Change what you want.

Spreadsheet courtesy of Rod Stewart."
 
it did have a 21p on there and

it did have a 21p on there and 3000 was all i got.so then i droped pitch to a quicksilver 15p and 3800 at 29 mph is all im geting
 
"Forgot to upload it.

<cent

"Forgot to upload it.

<center><table border=1><tr><td>http://www.marineengine.com/discus/icons/mime_msexcel.gif""" align=left alt=""application/vnd.ms-excel"">prop finder
[url=""][b]Copy of Copy_of_Boat_Speed_Finder-79780-193827.xls[/b][/url] (26.1 k)</td></tr></table></center>"
 
Are you trimming (raising&

Are you trimming (raising) the OD while under way to get the max. RPM w/o over revving the engine? Your engine is rated at 4400 - 4800 RPM. Are you running a 2 BBL carb? = 4500 - 4600 RPMs. A 4 BBL = 4700 - 4800 RPMs.
 
"[i]this 4.3 has ran like this

"this 4.3 has ran like this since i put it in it's used came out of a 96 regal. the other 4.3 that was in my boat ran at 4500

All this advice about props is like prescribing a bandaid for cancer...

fix the engine.

The fix is on the list Bondo linked to.

If the problem came with the replacement engine, fix the engine."
 
If the engine has been properl

If the engine has been properly tuned the performance will be optimized. I run a 4.3L 175 hp in my 3200 lbs. 19' boat and use a 19P 14.25" SS prop. It maxes out at 4600 RPMs on smooth water w/the OD trimmed. Tune/time the engine and borrow a 17P 14.25" to 15.25" SS prop and see what you get. What is the diameter of your prop? Is it cupped? Aluminum or SS?
 
What are the specs(HP/Torq

What are the specs(HP/Torque@?RPM) for the buick regal compared to the marine engine specs...I would think the cam profiles are different???
 
Is your prop slipping? Is the

Is your prop slipping? Is the engine coupler about to smoke itself? You would smell burned rubber.
 
the moter came out of a boat.

the moter came out of a boat. the prop dia is15 1/2 Aluminum. and i dont smell no ruber but will check.
 
"Have you checked the boat tac

"Have you checked the boat tach with a remote tach hooked to the engine?
Timing - is it advancing as the RPM increases?
Setting it correctly at idle does not mean it is advancing properly.
Is the throttle plate fully open at WOT?
Does it start bogging or lugging as it gets to 3800? check the entire fuel system - plugged fuel tank vent line, low fuel pressure from the pump, stuck anti-siphon valve, kinked fuel line,
dirty fuel filter (there is one on the carb too),
bad fuel (how old is the fuel?). Is the choke plate open when it's warmed up and stays open? Is the carb throttle plate fully open at WOT?"
 
"[b]"but just cant get her

""but just cant get her past 3800 under load and the moter is burning alot of fuel.
i have checked every thing"

Ayuh,... Obviously Not,....

I guess I be lookin' at the Carb,...
What do the Sparkplugs look like,..??
Has the Drive been off lately,..??

Don's list I linked to has 15 points of Interest,...
What are Your answers to those 15 Points,..??

Here,... I'll make it Easier...
"Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.
__________________

Don S."
 
Alum. 15P prop pushing a 21&#3

Alum. 15P prop pushing a 21' FG boat; too much blade flex. Do the basic tune-up first. Choke not opening all the way.
 
"Possible crossed wire....inco

"Possible crossed wire....incorrrect firing order? Cracked distributor cap? Run it in the dark to check for high voltage leakage between plug wires...are all cylinders of equal strength? Disconnect one plug wire at a time and check for equal RPM drop. What parts from the old engine were transferred to the new engine? If you checked the posts of Henry S. and Bondo, there isn't too much else to consider"
 
thanks every body for all the

thanks every body for all the good info. bob when the moter was out i spent the $$$$$ for all new parts.cause i did not want to deal with Replacing worn out parts all the time.
 
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