1999 7.4 (L29) only hitting 3400RPM at WOT

[1990dtgl98]

Hey y'all.

Bought a 1999 sea ray that ran but stumbled and misfire. It also surged and wouldn't hold idle. Since I had some free time in the spring I was able to do some work. All new as of this spring:

-Siphoned old gas. The previous owner didn't run it last year and the gas was at least 2 years old, smelled like paint thinner and looked off in color. I siphoned all of it out completely. Replaced the anti siphon valve and fuel water separator.
-Fuel pressure regulator
-Fuel pump
-Spark plugs (gapped .045)
-Cap and rotor
-Ignition coil
-Impeller

Set the base timing to 8* at 1800rpms. Fuel pressure is 39ish psi at idle. Idles at around 700rpm, fires right up cold or hot.

Finally got the family out and it ran great. It has a slight vibration but it doesn't feel like a misfire (need to check alignment). Decided to do a quick WOT run to confirm all was well, and that didn't go so well. WOT I was only able to get 3400rpm and 34mph. I do have a captains choice exhaust so I switched it to through hull (straight pipe) and it made no difference, still about 3400rpm and 34mph.

Speed was checked via GPS. 2 adults, 2 kids, 30gal gas. 26p props on a bravo 3 drive.

I'm thinking it's not exhaust if there was no change. The last thing I changed was the fuel pump and regulator (old one only had 26psi at idle). I ran it before changing it (and checking pressure) and could only get 2000rpm and the whole time it was backfiring out the intake and exhaust.

Could it be I need to replace the plugs again? Perhaps their coated since the pressure was so low previously? Any other ideas? Not sure where to go from here....

 

[dubs283]

Set the base timing to 8* at 1800rpms. Fuel pressure is 39ish psi at idle.

did you have the ignition system in base timing mode?

fuel pressure sounds about right, iirc spec is 40-43 psi throughout the rpm range

should also check fuel system vacuum, no more than 2 in/hg

 

[Scott Danforth]

what is fuel pressure at WOT? 39 is low

you may need to send the injectors out for cleaning and flow balancing.

 

[alldodge]

Agree "base timing mode"

Which searay is it (looking for weight and drive ratio)?
Depending on the boat the 26 pitch props might be a bit to high. Props might have been changed, compression might be low

 

[1990dtgl98]

did you have the ignition system in base timing mode?

fuel pressure sounds about right, iirc spec is 40-43 psi throughout the rpm range

should also check fuel system vacuum, no more than 2 in/hg

Ignition was in base timing with pins jumped on the dlc connector.

what is fuel pressure at WOT? 39 is low

you may need to send the injectors out for cleaning and flow balancing.

I didn't check at wot (kids with me, didn't want to wot with earmuffs), but setting base timing it was 41psi at 1800.

Agree "base timing mode"

Which searay is it (looking for weight and drive ratio)?
Depending on the boat the 26 pitch props might be a bit to high. Props might have been changed, compression might be low

1999 230 bowrider. According to the searay resource page, it should be a 26 pitch prop set and hit 4600rpm.

 

[dubs283]

Ignition was in base timing with pins jumped on the dlc connector.

okay, have you verified timing is advancing?

should check fuel pressure at wot under a load and still a good idea to check fuel system vacuum at the same time

454 in a 23 foot sea ray? that boat should do 50 mph easy with more to go

 

[1990dtgl98]

okay, have you verified timing is advancing?

should check fuel pressure at wot under a load and still a good idea to check fuel system vacuum at the same time

454 in a 23 foot sea ray? that boat should do 50 mph easy with more to go

I'll try to get a friend out and go kidless to check.

Checked timing and it is advancing. Again, just at lower rpms but off base timing it does jump up. When you say fuel system vacuum your just talking the vacuum line running to the pressure regulator?

According to other owners should do about 52-55 at 4600 with a light load.

 

[dubs283]

When you say fuel system vacuum your just talking the vacuum line running to the pressure regulator?

no

check vacuum between the fuel pump and the tank, this will tell you how much vacuum the fuel pump is creating to draw fuel from the tank. should be no more than 2 in/hg, any more indicates a restriction between the tank supply and the pump

 

[1990dtgl98]

no

check vacuum between the fuel pump and the tank, this will tell you how much vacuum the fuel pump is creating to draw fuel from the tank. should be no more than 2 in/hg, any more indicates a restriction between the tank supply and the pump

What would I use to check that....and where would I check it?

 

[alldodge]

Use a short piece of fuel line and a Tee fitting. Place the Tee between fuel tank and filter. Connect a vacuum gauge to the Tee

https://www.harborfreight.com/fuel-pump-and-vacuum-tester-62637.html

 

[tank1949]

Hey y'all.

Bought a 1999 sea ray that ran but stumbled and misfire. It also surged and wouldn't hold idle. Since I had some free time in the spring I was able to do some work. All new as of this spring:

-Siphoned old gas. The previous owner didn't run it last year and the gas was at least 2 years old, smelled like paint thinner and looked off in color. I siphoned all of it out completely. Replaced the anti siphon valve and fuel water separator.
-Fuel pressure regulator
-Fuel pump
-Spark plugs (gapped .045)
-Cap and rotor
-Ignition coil
-Impeller

Set the base timing to 8* at 1800rpms. Fuel pressure is 39ish psi at idle. Idles at around 700rpm, fires right up cold or hot.

Finally got the family out and it ran great. It has a slight vibration but it doesn't feel like a misfire (need to check alignment). Decided to do a quick WOT run to confirm all was well, and that didn't go so well. WOT I was only able to get 3400rpm and 34mph. I do have a captains choice exhaust so I switched it to through hull (straight pipe) and it made no difference, still about 3400rpm and 34mph.

Speed was checked via GPS. 2 adults, 2 kids, 30gal gas. 26p props on a bravo 3 drive.

I'm thinking it's not exhaust if there was no change. The last thing I changed was the fuel pump and regulator (old one only had 26psi at idle). I ran it before changing it (and checking pressure) and could only get 2000rpm and the whole time it was backfiring out the intake and exhaust.

Could it be I need to replace the plugs again? Perhaps their coated since the pressure was so low previously? Any other ideas? Not sure where to go from here....

That's A LOT OF BASE TIMING rpms. TB 4 or 5 with Knock control????? Perhaps you disconnected wrong wire for base timing set? Also, check fuel lines and tank tube pickup for clogged filter. Some pick up tubes have screens inside them. Trust me!!!!! You may want to buy a cheap 12 volt fuel pump and recycle clean gas into tank through filter until all crap is removed into filter.

 

[dubs283]

That's A LOT OF BASE TIMING rpms. TB 4 or 5 with Knock control????? Perhaps you disconnected wrong wire for base timing set?

yeah, op's engine is an efi mefi controlled ignition/fuel system. base timing mode will usually advance throttle automatically, if not 1500 rpm is considered spec for timing on these motors. 1800 may be a little high but won't hurt anything

454 can handle close to 40 degrees advance at higher rpm considering stock application

 

[1990dtgl98]

That's A LOT OF BASE TIMING rpms. TB 4 or 5 with Knock control????? Perhaps you disconnected wrong wire for base timing set? Also, check fuel lines and tank tube pickup for clogged filter. Some pick up tubes have screens inside them. Trust me!!!!! You may want to buy a cheap 12 volt fuel pump and recycle clean gas into tank through filter until all crap is removed into filter.

Manual states 8* at 1800rpm. Wire wasn't disconnected, its jumping pins a and b on the connector for diagnostic hookup.

I did replace the line from the tank to the filter, the fuel water filter itself (twice), and the anti siphon fitting. I did not replace the pickup tube (looked fine, screen looked ok).

yeah, op's engine is an efi mefi controlled ignition/fuel system. base timing mode will usually advance throttle automatically, if not 1500 rpm is considered spec for timing on these motors. 1800 may be a little high but won't hurt anything

454 can handle close to 40 degrees advance at higher rpm considering stock application

the engine did advance to 1500rpm but the service manual did say manually advance to 1800.

 

[tank1949]

Manual states 8* at 1800rpm. Wire wasn't disconnected, its jumping pins a and b on the connector for diagnostic hookup.

I did replace the line from the tank to the filter, the fuel water filter itself (twice), and the anti siphon fitting. I did not replace the pickup tube (looked fine, screen looked ok).


the engine did advance to 1500rpm but the service manual did say manually advance to 1800.

Not familiar with specific ignition system, but have you revved motor while using timing light to watch or make sure distributor advances????

 

[1990dtgl98]

Not familiar with specific ignition system, but have you revved motor while using timing light to watch or make sure distributor advances????

I did up to about 2000rpms and it does advance