knotguilty

Looks great! What kind of thread did you use?

I love the roar of my boat when it is idling but I didn't care for the overly loud exhaust when i was cruising down the lake. By the end of the day my crew and i were all def between the music and the exhaust. I have seen many posts on this topic but I didn't see one this inexpensive so i figured i would share. I installed these in my 4" exhaust tubes going from the Sideswipe valve to the exhaust tip. It took me about 30 minutes per side and cost me ~$100 with shipping. I saw no loss in power the boat is somewhat quieter going down the lake but the real magic happens when I switch my exhaust to one side. It almost goes silent. A bit like captains call. I saw almost no reduction in idle sound with both exhaust ports open. Perfect for me. Here are the silencers I installed: http://www.cpperformance.com/p-12622-4-slip-in-silencer.aspx Here are some pictures of my install. Basically came down to drilling one hole in the exhaust tube to hold the silencer in place. Hardest part was taking the tubes out. Came down to brute strength and ignorance.

The belief now is that the fuel pressure regulator drove the injectors to force open. I cleaned them all with injector cleaner and did a balance test before hitting the lake. All good so far.

Problem solved! I did a balance check on my new injectors (500 ms and 20 cycles) fuel pressure dropped 9-10psi. I put the old injectors back in and 8 psi drop. 20% more fuel from the new injectors. Looks like China replacement injectors are not the place to save some dough. I left the old injectors in and went out on the boat all day Sunday. She purred like a mountain lion! No black streak on the side of the boat either!

Video of my vacuum gauge and RPM on the scan tool. https://youtu.be/XqJKj1Keu5g

I replaced the fuel pressure regulator in the cool fuel box and the fuel pressure looks steady now but is still running high around 38 psi. The idle is still rough, sounds a bit like a Harley in the water. Sounds like "potato potato potato". The exhaust still smells really rich and I get a black layer of soot like stuff all over the hull near the exhausts (Sideswipe). Vacuum is still running low 12 inhg. Which may explain the high fuel pressure and rich idle. Compression looks good. I can't explain the low vacuum. I've measured it straight at the intake manifold and still low. I have a 555 ECM so timing should be good but I checked it with the scan tool and it is bouncing all over at idle. Rpm is also bouncing between 575 and 630. Does anyone know where the ECM gets RPM? Cam position sensor? One more note, I checked the duty cycle at the IAC. The computer and the duty cycle gauge read the same. I tried 2 new IACs and they reacted the same. They didn't move when not on the engine but I have to assume the airflow helps push the actuator.

I replaced the fuel pressure regulator in the cool fuel box and the fuel pressure looks steady now but is still running high around 38 psi. The idle is still rough, sounds a bit like a Harley in the water. Sounds like "potato potato potato". The exhaust still smells really rich and I get a black layer of soot like stuff all over the hull near the exhausts (Sideswipe). Vacuum is still running low 12 inhg. Which may explain the high fuel pressure and rich idle. Compression looks good. I can't explain the low vacuum. I've measured it straight at the intake manifold and still low. I have a 555 ECM so timing should be good but I checked it with the scan tool and it is bouncing all over at idle. Rpm is also bouncing between 575 and 630. Does anyone know where the ECM gets RPM? Cam position sensor? One more note, I checked the duty cycle at the IAC. The computer and the duty cycle gauge read the same. I tried 2 new IACs and they reacted the same. They didn't move when not on the engine but I have to assume the airflow helps push the actuator.

Are you using non detergent Oil? I made the mistake of putting a little normal oil in and the oil foamed up on me and caused the light to go off at higher RPMs. Took 2 complete oil changes to get about 1/4 quart of "detergent oil" out.

So back to the fuel pressure. Sounds like replace the fuel regulator on the cooler first and go from there?

Yes, that is my engine. Made the videos last night. Not sure what you mean by cross fire distributor cap. The cap is not Murcruiser. It is a standard 350 small block rotor and cap.

I tested the vacuum as well tonight. Runs between 10-12 hg in. Sounds low but my plugs are covered in soot so I'm guessing my valve seals are too. Check out these videos: https://youtu.be/eQfp6N1H00k https://youtu.be/i7QScZVQ2hg

Tommy, Thanks for testing. That helps. Was the fuel pressure steady? Sent from my iPhone using Tapatalk

I have a Rinda. I paid almost $400 for it 4 years ago. I believe that is the cheapest option to check the codes on a Merc. At least the cheapest I have found.

I checked my fuel pressure. When I turn the key the pressure is rock solid at 43PSI until the pump goes off. Once the pump stops and before I start the boat the fuel pressure drops to 38PSI. Once i start the boat the pressure bounces between 36 and 43PSI at idle. I tested this in the driveway so I didn't go to higher RPMs. Is it normal for the fuel pressure to bounce erratically at idle? I'm thinking I may need a new regulator. The one on the fuel cooler. Apparently the regulator on the rail is a dummy but can still go bad according to the manual. Yeah for extra parts! As far as the IAC and the computer all is good there. I checked the DC and AC volts and everything checked out. Even though the control is a square wave duty cycle RMS voltage tells me the control is sending the right signal. I measured the voltage from the Black and Green wire (IAC grounded control) and the sky post (best ground I could find). Results below for reference: %Duty Cycle (Rinda) AC(V) DC(V) 100 0.0 0.0 90 2.3 1.15 80 4.4 2.26 70 6.6 3.35 60 8.7 4.46 50 10.8 5.54 40 12.8 6.64 30 14.7 7.27 20 16.6 8.81 10 18.5 9.87 0 19.9 10.74 Before engine start the valve was controlled to 0% and idle immediately after start was at 100%.

Checking the pressure on a good running boat would be helpful. Also if anyone has a Rinda and wouldn't mind running a IAC test and let me know how much the RPMs change. Mind does not change at all which has me concerned. My fuel pressure gauge comes in today so I should know more this evening.