4.3 mercuiser no power to plane out

[ardelly67]

i have a 96 vip with 4.3 mercruiser just had head redone new valves.got it on lake last week and gave her full throttle and 2000 rpms is all she would get never anymore.changed plugs today and gas treatment.any ideas what might be the problem.the motor runs great.if not in gear revs 4000 rpms not a miss in her.it does not pop or miss or sound bad when in gear at full throttle just now more go to get on plane.please help!! thanks

 

[jtmarten]

Re: 4.3 mercuiser no power to plane out

Getting rpms in neutral and getting them with a load are two completely different situations. Revving in N means nothing.
There are a multitude of things that can cause this.
prop too big
improper or no timing advance
clogged fuel filter
bad fuel pump
obstructed fuel line
fouled spark plugs
bad plug wire(s)
bad coil
throttle linkage not allowing full throttle
cam improperly timed when assembled (if timing set removed)
etc
etc
etc

 

[ardelly67]

Re: 4.3 mercuiser no power to plane out

i have moved the distributer both ways while under load did not emprove.i tried sprayn gas into carb while under load just made it bog down.ive got a new cap and rotor being shipped to me friday did plugs today.and the prop is the same one ive had for two years.throttle linkage opens carb full throttle also.on the coil dont know never checked it.how can i check the coil?

 

[wire2]

Re: 4.3 mercuiser no power to plane out

......on the coil dont know never checked it.how can i check the coil?

Remove the HV lead from the center of the distributor, then gripping it lightly with insulated pliers, hold the end ~?" from the engine. Have someone crank the starter for a second or 2. You should see a fat blue spark for each cylinder coming to TDC on compression. If it's a wimpy red spark, check the points gap, rotor. Is the flame arrester on the carb clean?

 

[ardelly67]

Re: 4.3 mercuiser no power to plane out

mine has the tunderbolt ignition no points.spark arrester is that the air breather? before i had the new valves put in the head the boat would still plane out just took a bit then it would take off to almost top speed.it had a sucked valve so it didnt have full power.now the motor sounds great.but now cant get on plane..

 

[jerryjerry05]

Re: 4.3 mercuiser no power to plane out

Check the timing.J

 

[jtmarten]

Re: 4.3 mercuiser no power to plane out

Timing; 34-36*, fully advanced by 3000rpm. Your TBIV should list the advance, usually 22* or 24*. Subtract that from 35, and that is what your timing at idle should be.

 

[45Auto]

Re: 4.3 mercuiser no power to plane out

Who pulled and replaced the heads? Who adjusted the valves? Do a compression test.

 

[Bondo]

Re: 4.3 mercuiser no power to plane out

Who pulled and replaced the heads? Who adjusted the valves? Do a compression test.

Ayuh,... My thoughts, Exactly....

 

[jerryjerry05]

Re: 4.3 mercuiser no power to plane out

What is the timing at idle?When the motor is hot reach in touch the coil if it's hot enough to burn it's probably bad warm/hot it's ok.J

 

[ardelly67]

Re: 4.3 mercuiser no power to plane out

my nephew has a shop that is where the work was done he sent the head of for the valves he and his other mechanic put it together.i will check the coil soon as i can.could the valves be to tight maybe?

 

[ardelly67]

Re: 4.3 mercuiser no power to plane out

ok got my problem fixed..very simple and over looked.two plug wires were crossed.weird thing it didnt miss or pop nothing.but they did not show a very hot spark till we swaped them around and the boat just jumped out on plane and hit fifty like nothing was ever wrong..lol saved me alot of money not have to change parts till i found the problem..thanks to all that gave me advice