Welcome to the Cummins Marine Community
At Seaboard Marine, we live and breathe Cummins Marine Diesel... the community forum is a place where you can share your experiences, ask questions about your Cummins Marine engines & products, and interact with others in the boating community for FREE. Please note that you must be registered on www.sbmar.com in order to create topics in the community forum.
Welcome, Guest! Please Register if you would like to create topics in the community forum.
This forum contains 5,598 Topics, 26,418 Replies, and 16,021 Contributing Members.
-
- Cummins Marine Forum Topics
-
-
What is this valve/port for? Cummins QSB 5.9
This topic has 2 replies, has 2 voices, and was last updated by
11 hours ago
May 10, 2025 at 6:44 pm What is this valve/port for? Cummins QSB 5.9. Can it be deleted?
Started by:
in: Cummins Marine Engines
2 RepliesMay 13, 2025 at 8:40 pm Hi Rob, Thank you for the helpful info. There was an outlet on the other side of the block for an A/C defroster so this must have been the return for that circuit. I will remove the valve because it is in the way of the oil filter line connectors. DavidLast Post by:
-
6BT 5.9 (CPL 0742) upgrade to 19SI alternator
This topic has 4 replies, has 2 voices, and was last updated by
12 hours ago
May 12, 2025 at 12:32 pm I currently have the original Motorola/Prestolite 65A alternators on the two 6BT 5.9 engines in my 1987 OA420 (CPL 0742). I would like to swap them for two 19SI alternators in 105A or higher. I did a test fit with an old 19SI and it looks I need a different alternator brace. Is your part 3934941 what I need? Is anything else needed to do this update? I’ve attached a photo of the test-fit 19SI in place (with wrong pulley and belt routing note…
Started by:
in: Cummins Marine Engines
4 RepliesMay 13, 2025 at 7:52 pm Tony, I have studied your site extensively before asking the questions I have. If you can point me to where they are answered, I will gladly admit I am wrong. So, let me restate the questions: 1) Is the part listed on your site under the heading “Cummins Marine 19SI Alternator Brace (3934941)” the correct alternator brace to install a 19SI alternator on my 6BT 5.9 CPL 0742 engines? I have done a hands-on test fit of a borrowed “dead” 19SI and…Last Post by:
-
QSC 8.3 will not start, will not crank
This topic has 5 replies, has 4 voices, and was last updated by
16 hours ago
May 11, 2025 at 1:59 pm I have a 2003 Sea Ray 460 with 2020 QSC 8.3’s approx. 65 hrs to date. Port engine will not start, will not crank. Can hear solenoid engaging and have checked solenoid. It seems to be fine. Could the issue be with the mag switch coil? Thank you for any help!
Started by:
in: Cummins Marine Engines
5 RepliesMay 13, 2025 at 3:34 pm After checking mag switch with multimeter, checking batteries, grounds and all connections, it is looking like a starter issue. I am a little surprised that the starter is shot on 2020 QSC 8.3 with only 65 hrs. Has anyone experienced starter issues with so little age and hours? Also can anyone give me any insight as to how the replacement is going to go? As I said its a 2003 460 Sea Ray that was repowered 2 1/2 years ago with 2020 8.3’s. N…Last Post by:
-
2014 QSB 6.7 questions and service
This topic has 4 replies, has 3 voices, and was last updated by
16 hours ago
May 8, 2025 at 8:51 am Looking at a boat with 2014 QSB 6.7 375HP Boat launched in 2014 and in salt water under that owner until 2020– boat had 400ish hr’s in 2020 when new owner purchased. In late 2020 new owner discovered one of the aftercoolers was dripping seawater into bilge– tech suggested and owner agreeded to replace both aftercoolers. — Boat had 500 hr’s Boat now has 1500 hrs and service records show yearly oil and filter changes …
Started by:
in: Cummins Marine Engines
4 RepliesMay 13, 2025 at 3:12 pm Thanks for the info — we go to survey in a few weeks — if all checks, we will purchase and then pull the aftercoolers and do As Tony Suggests — 1 more question– attached is a picure of the aftercoolers that were put on as new in 2020 — looking at the photos identifying which aftercooler you have, it looks like the boat has the “new Mota Post 2021” could this aftercooler have been put on in 2020? &…Last Post by:
-
6bta 370 Issues with compression test
This topic has 0 replies, has 1 voices, and was last updated by 17 hours ago
May 13, 2025 at 2:35 pm Hello All, I recently went for a ride and the push rod cover gasket gave way and blew out alot of oil. Oil pressure dropped to 0 and motor started limp and run rough. The second it happened I turned of the motor. After investigating and alot of cleaning i found multiple spots leaking from push rod cover gasket. I refilled with 4 quarts it had lost and started it back up. It was running rough and rpms would not come up. Oil pressure came back but…
Started by:
in: Cummins Marine Engines
0 Replies - Can you Help? ...be the First to Respond!
-
Temp and oil pressure alarms ?
This topic has 2 replies, has 3 voices, and was last updated by
20 hours ago
May 8, 2025 at 10:52 pm Hi all. Have a QSB 5.9. I’m looking at putting alarms or some display that I can set to tell me if we have an overheat or oil pressure drop etc. When it gets to a certain temp it alarms loud up in the dash area. Maybe a MFD unit hooked up to the electronics. I’m not certain. I had an overheat and don’t want it to happen again. I was under the impression that there was alarms under the dash. But no. ? Well they did not go off anyway. Any help wou…
Started by:
in: Cummins Marine Engines
2 RepliesMay 13, 2025 at 11:20 am After an impeller shredded, resulting in an overheat, I installed pressure gauges directly off the sea water pumps. Also have direct contact sensors on the injection elbows that are wired to an idiot / alarm panel that Tony sells. The overheat resulted in a cracked exhaust manifold, piston beginning to melt etc. We did an in frame rebuild, around 14K. Leaving the marina we had normal water flow out the exhaust, about 2 minutes after getting o…Last Post by:
posted: 20 hours ago
-
Cummins 6BT 210hp White Smoke and wont get to temp
This topic has 11 replies, has 4 voices, and was last updated by
1 day ago
May 5, 2025 at 12:38 pm Hi Guys, First post here and hoping I can get some help because I am stumped… 2000 Terry Jason 28 with a 6BT 210HP. The boat starts with a touch of the key hot or cold. Runs amazing, zero blow by, reaches correct WOT RPM, etc. My issue im having here is the boat has a white fuel smoke at idle and underway. It has done this since i bought the boat last year. Over the winter, I had the injectors rebuilt and tested, very reliable shop.…
Started by:
in: Cummins Marine Engines
11 RepliesMay 13, 2025 at 4:27 am Sounds like you’re chasing a frustrating issue. White smoke at all times and consistent low temps could point to overcooling. If the thermostat is correct and working, double-check the bypass and raw water flow setup some boats have plumbing quirks that prevent the engine from reaching proper temp. Also worth checking if the coolant temp sensor or gauge is reading low. Overfueling can contribute to white smoke, but usually you’d see …Last Post by:
posted: 1 day ago
-
Muffler install – Connection size (Reduce)?
This topic has 1 reply, has 2 voices, and was last updated by
1 day ago May 12, 2025 at 1:03 pm I have what I thought was a 6″ exhaust pipe, and I bought a new muffler with a 6″in/6″ out. I assumed the options for pipe size was 6″ then 8″. But I think my current pipe may be 6 1/2″ od. my question is can a 6″ ID silicone exhaust hose stretch enough to go around a 6 1/2 pipe? It will fit on the muffler no problem. or is there a better option? Do I need to find a way to reduce the existing pipe down 1…
Started by:
in: Cummins Marine Engines
1 ReplyMay 13, 2025 at 3:45 am No on the stretch option. There is 6-5/8″ exhaust hose out there and then you can add a ~1/4″ sleeve to the muffler ports. Rob "Luck is the residue of good design."Last Post by:
posted: 1 day ago
-
Mag switch, starter control relay
This topic has 0 replies, has 1 voices, and was last updated by 1 day ago
May 12, 2025 at 2:49 pm Is the mag switch or starter control relay prone to failure? I have 2020 QSC 8.3’s with only 65 hrs and port engine will not start or crank.
Started by:
0 Replies - Can you Help? ...be the First to Respond!
-
Cummins Reman 6BTA 330HP Momentary Smoke During Acceleration
This topic has 1 reply, has 2 voices, and was last updated by
2 days ago May 11, 2025 at 5:03 pm I own a 32 Luhrs Open with twin Reman 6BTA 330hp engines with about 200 hours. Recently I installed CCV kit/air filter and cleaned /greased aftercooler on both engines. When running the boat above 1600-1800 rpms and I increase the throttles I get a 1-2 second puff of black smoke from both engines then both exhausts clear up. When I cleaned/painted the hull last Sept both engines would make 2850 rpms at WOT. Now they both make about 2750 rpm…
Started by:
in: Cummins Marine Engines
1 ReplyMay 12, 2025 at 6:26 am You could dial it in and remove 1 inch(or more) of pitch from the props so that your clean normally loaded situation nets out a 2940 WOT rpm. 2800 * 1.05 = 2940. Tony recommends being able to achieve 105% of rated rpm. The transient dark smoke is what I would consider normal when advancing throttles. These are mechanical engines so the increased delivery in fuel is faster than the turbo and the resulting increase in intake air volume. You ge…Last Post by:
posted: 2 days ago
-
Cummins/Glendinning throttle problem
This topic has 6 replies, has 3 voices, and was last updated by
2 days ago May 9, 2025 at 6:04 pm Hi all. I am hoping someone out there can help. My launch has twin QSB5.9s in it controlled by electronic throttle with a single helm. The intermittent problem I am having is that when we are cruising along with the motors in ‘sync’ mode one motor will drop out of sync and then slowly drop is revs down until eventually it just goes into limp mode. No alarms come up on the throttle control. I believe the ets unit is a Cummins/glendinning EEC4. Th…
Started by:
in: General Discussion
6 RepliesMay 11, 2025 at 2:18 pm Go to the Glendinning web site Seaboard Founder & PresidentLast Post by:
posted: 2 days ago
-
Expected BOOST for QSC 540
This topic has 5 replies, has 2 voices, and was last updated by
2 days ago
May 8, 2025 at 8:23 pm Hello. Does anybody have an idea of what the expected turbo boost be at cruising and at WOT for a qsc 8.3 540?
Started by:
in: Cummins Marine Engines
5 RepliesMay 11, 2025 at 10:34 am Understood. In the case that the mechanical gauges were to confirm the same numbers which turrbo / engine would you think is perfoming incorrectly? I was thinking that if a turbo would not be able to reach the boost required that maybe the other engine would be overcompensating for it.Last Post by:
-
QSM 11 Manifold Temperature and After cooler
This topic has 3 replies, has 2 voices, and was last updated by
2 days ago May 10, 2025 at 8:36 pm Tony I have 2 questions. QSM 11 670 HP 2007 4100 hours Question 1. I just put in a new after cooler core due to a small saltwater leak out of my condensation drain (caught in time thank goodness) so my key question is you taught me how to service my after coolers back in 2012 and you liked the job I did so you asked me to send you photos which I did. So I failed to put the red RTV on the new core like I did back in 2012 and the new core didnR…
Started by:
in: Cummins Marine Engines
3 RepliesMay 11, 2025 at 8:03 am The RTV is there to make more hot air passes thru the fins.. Your IMT numbers are “not to worry” so I would not bother…………May I ask what you paid for a core? They are super expensive from Cummins. Seaboard Founder & PresidentLast Post by:
posted: 2 days ago
-
Low coolant level alarm.
This topic has 1 reply, has 2 voices, and was last updated by
3 days ago May 4, 2025 at 10:12 am I have 2006 QSM11 675’s. Starting at the end of last season the alarm for “low coolant level” went off on a few occasions. After checking and confirming no coolant loss and engine temperature remined normal and constant I replaced the sensor. Seemed to have worked for a while (questionable). This season it happened very quickly after launching boat from the hard. Checked the levels and temperature – all normal. I had rea…
Started by:
in: Cummins Marine Engines
1 ReplyMay 10, 2025 at 5:51 pm so the same thing happened to me two times. Coolant level was fine. Hasn’t happened since. I had to replace a head due to a broken bolt that was drilled out and tapped had a very bad angle. It kept breaking exhaust manifold bolts. People that serviced my engine seven years ago must’ve broken the bolt and did not tell me. Upon removal of the head, we found some minor traces of antifreeze possible freeze plugs minor leak. Back together now and no …Last Post by:
posted: 3 days ago
-
Break-in
This topic has 4 replies, has 3 voices, and was last updated by
6 days ago May 5, 2025 at 3:26 pm Hello I recently re-powered with a 5.9 6BTA. Looking to find more information on recommended break in procedures. I was able to find this on this page but not much else “In the absence of these (seems like most cases), break-in for the first few hours should consist of a mix of short time (5-15 seconds) full power use, along with at least 10-25 % of these first few hours at 70-80% of full power.” How long should the break-in period b…
Started by:
in: Cummins Marine Engines
4 RepliesMay 8, 2025 at 7:06 am I wouldn’t over complicate this. Per the manual: The new Cummins® engine associated with this manual does not require a “break-in” procedure. This section of the manual provides all of the necessary information required for proper engine operation. Per our article: break-in for the first few hours should consist of a mix of short time (5-15 seconds) full power use, along with at least 10-25 % of these first few hours at 70-80%…Last Post by:
posted: 6 days ago
-
Old zf trans
This topic has 0 replies, has 1 voices, and was last updated by 6 days ago
May 8, 2025 at 5:40 am Hello all. I have zf hurth HSW 800 A2 transmission and would like to purchase rebuilt kit for it. I see Tony got kit for 85A trans….does it fit mine? Thanks people.
Started by:
in: Marine Transmissions
0 Replies - Can you Help? ...be the First to Respond!
-
Real Basic Coolant Questions
This topic has 0 replies, has 1 voices, and was last updated by 6 days ago
May 8, 2025 at 4:21 am I have twin QSC-500s and noticed the coolant level appears to be a bit low in my starboard engine. The expansion tank on the port engine is about half full. The expansion tank on my starboard engine only has about an inch in it. Both of these are when the engine is cold. Also, the starboard engine expansion tank went down about an inch last time I used the boat. In both engines, when I look in the top of the engine, I do not see the coolan…
Started by:
in: Cummins Marine Engines
0 Replies - Can you Help? ...be the First to Respond!
-
Intermittent floating RPM’s 6CTA
This topic has 0 replies, has 1 voices, and was last updated by 6 days ago
May 7, 2025 at 7:36 pm Hello, I have a pair of 2000 6CTA8.3 Diamond 450’s with about 1100 hr’s on them. The port side engine when under load at 1700rpm’s will intermittently come down to about 1600rpm’s and then surge to about 1750rpm’s. (see video link below) I initially thought it could be the synchronizer, but it still happens when the synchronizer is powered off. I’ve also replaced all the fuel filters and am still seeing the issue. T…
Started by:
in: Cummins Marine Engines
0 Replies - Can you Help? ...be the First to Respond!
-
QSB 425 hp oil pressure sensor location
This topic has 4 replies, has 2 voices, and was last updated by
6 days ago
April 28, 2025 at 4:20 pm I need some help here guys. Last year I had a fluctuating oil PSI reading on my port engine. I went ahead and got a new sensor from SBM and today went out to put it in. Looking at the parts diagram it shows it behind the metal plate that the electronic modules are on, left side of engine. I took off the smaller front plate and was able to bend it back out of the way. I did not see what looked like the sensor, what I saw was a maybe 1/2″ …
Started by:
in: Instrumentation & Electronics
4 RepliesMay 7, 2025 at 1:42 pm I went out and took it off today. Working upside down with my glasses sliding off made it no fun but you can see how I would be concerned about it. At first I thought there was a plastic cap over the top, like some electronic connections I have worked with. But no, it’s just different. Before installing the new one I called SBMAR parts and spoke with Marco. The new one is correct, just superseded in design and part number.Last Post by:
-
6CTA Oil seeping Rear Main Seal?
This topic has 5 replies, has 3 voices, and was last updated by
1 week ago
April 24, 2025 at 6:48 am I am tracking down a very minor oil seep on my 2002 6CTA I’m thinking I traced it back to a rear main seal but wanted to get some additional insight. The oil drops in the bilge are minor maybe a half an ounce after running for an hour. I noticed some minor oil on the trans line and the turbo outlet hose. Banjo bolt is dry as a bone. Any thoughts other than rear main? Looks like I have a nice winter project. If it is rear main can I simply …
Started by:
in: Cummins Marine Engines
5 RepliesMay 7, 2025 at 4:47 am I will certainly post back, Motor mounts are on my list as well as trans hoses, trans cooler, turbo gaskets, banjo bolt, looks like I should get away without completely pulling running gear and just sliding back the coupler so I may change the dripless seal as well while I’m there. I hate not replacing seals/gaskets only to leak when they’re back in the water. I don’t plan on doing this project until November but will post bac…Last Post by:
-
What is this valve/port for? Cummins QSB 5.9
