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This forum contains 5,739 Topics, 27,002 Replies, and 16,551 Contributing Members.
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- Cummins Marine Forum Topics
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Hurth 800 A2 and trolling valves
This topic has 3 replies, has 2 voices, and was last updated by
10 hours ago March 6, 2025 at 11:37 am Hi all. I’m in the UK, and have a 38′ motorboat with twin 6BTA’s 250hp CPL 1322, with Hurth 800A A2 20 gearboxes. These engines have the Nippon Denso EP9 fuel pumps, and they do not idling too much. The boat will go 23 knots but cruise at 13 – 18 knots. At an idling speed they go 8.5 knots, or on one engine 4.5 knots. The intended use is 40 miles up the coast to the Norfolk Broads inland waterways, 70 miles to the up…
Started by:
in: Marine Transmissions
3 RepliesAugust 28, 2025 at 5:40 pm On this gear, the trolling valves are very “touchy” at best and difficult to operate at even settings You must stay below 1000-RPM if you engage them Sounds like your Nippon EP9 Pump needs work on the Bumper spring and the related parts–Don’t ask as I can’t help ( those days are gone) but you may find help with some searching on google Seaboard Founder & PresidentLast Post by:
posted: 10 hours ago
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2007 QSB
This topic has 1 reply, has 1 voices, and was last updated by
12 hours ago
August 28, 2025 at 3:11 pm I need some suggestions– I have been looking for the right boat for a number of months and still have not found it. I am currently looking at one several plane rides away from me, and I would like thought before I spend the time and money to go see it. Boat is a 2007 with 380 hp QSB with 1560 hours. Boat was a freshwater boat until 2022. I have all the service records from 2022 until current — owner has done all services shop has su…
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in: Cummins Marine Engines
1 ReplyAugust 28, 2025 at 3:14 pm photos attachedLast Post by:
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Diesel Kleen
This topic has 5 replies, has 4 voices, and was last updated by
15 hours ago
August 27, 2025 at 2:49 pm Probably discussed already but any opinions in the regular use of Power Service Diesel Kleen in a QSB6.7? Cummins endorsed, you know! Lol. Prior posts discuss it’s use to solve issues. My question is ‘for ongoing use, does it help keep injectors clean and help offset diesel fuel inadequacies’. IOW, is it a benefit to a healthy engine? Blue Magnolia
Started by:
in: Cummins Marine Engines
5 RepliesAugust 28, 2025 at 12:33 pm Thanks to all for your replies. Very helpful. Blue MagnoliaLast Post by:
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Qsb 6.7 425hp Squeaking noise front engine can’t get rid of it
This topic has 5 replies, has 3 voices, and was last updated by
August 22, 2025 at 5:07 pm I got a 6.7 425hp Cummins started squeaking. I replaced alternator, coolant pump twice, idler bearing and new serpentine belt and noise is still there. You take belt off and no noise put belt back on noise.
Started by:
in: Cummins Marine Engines
5 RepliesAugust 28, 2025 at 12:33 pm You can’t tell with the naked eye. You have to put the laser tool on it to see the offset. Mine had the same noise. Blue MagnoliaLast Post by:
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6CTA cap leaking after 2nd replacement
This topic has 11 replies, has 5 voices, and was last updated by
22 hours ago
July 8, 2025 at 4:13 pm I’ve had a coolant leak since I’ve owned the boat approx 60 hours on new to me boat… replaced the cap and turbo to manifold gaskets the seaboard way pressure tested for 1 hour with success. Ran the boat for approx 12 hours and noticed coolant lose. Pressurized system and I lost about 7 psi over the course of an hour. Opened up the cap and saw coolant sitting in the manifold. Re-Replaced the new gasket sanded down manifold and cap with 80 grit an…
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in: Cummins Marine Engines
11 RepliesAugust 28, 2025 at 5:28 am If it’s worth anything I ended up replacing the cap manifold gasket the second time sanded and filed down the cap used a generous amount of RTV and resolved my issue. Was the turbo wet when you replaced the gaskets?Last Post by:
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Seawater Hose Selection
This topic has 1 reply, has 2 voices, and was last updated by
1 day ago August 27, 2025 at 9:07 am No problems at the moment but since certain engine hoses are up to 14 Yrs old, I’m thinking it might be smart to begin replacing them on my 2011 QSC8.3 (unknown if previous owner might have replaced some). The main seawater intake hose as in photo is a Trident. But from the strainer it goes about 9 feet under the engine to the water pump; that 9′ piece does not say Trident and I can’t find the manufacturer name. Cummins quickse…
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in: Cummins Marine Engines
1 ReplyAugust 27, 2025 at 10:46 am 14 years for a seawater hose is not much of a concern if all is well. There’s no much pressure and hoses don’t mind seawater but of course you need to look for things like chafing, etc. Wire reinforced hoses could have rusting of the wire coil. QSOL will not list this since the hose to the pump is a boat specific part, not a factory engine supplied part. I prefer the Shields 254 or Trident 252 for engine intake. I’ve used bo…Last Post by:
posted: 1 day ago
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Sea water in Envirovent puke bottle
This topic has 3 replies, has 3 voices, and was last updated by
1 day ago August 25, 2025 at 11:24 am Just noticed sea water in my Envirovent puke bottle- any suggestions as to where to look for the source? 1997 Cummins 5.9 6bta engine.
Started by:
in: Cummins Marine Engines
3 RepliesAugust 27, 2025 at 10:24 am Was also thinking the same as to how it was determined to be seawater. Rob "Luck is the residue of good design."Last Post by:
posted: 1 day ago
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QSB 6.7 Alternator Stretchy Belt
This topic has 1 reply, has 2 voices, and was last updated by
2 days ago August 25, 2025 at 8:34 am I am replacing the Alternator Belt on my QSB 6.7 380 HP. Is it acceptable to loosen the alternator bracket to install the belt, then extend fully to stretch the belt? CHJ
Started by:
in: Cummins Marine Engines
1 ReplyAugust 26, 2025 at 4:19 pm yes as that is the only way–Spray all with WD-40 or oil treads 1st as the 2-part paint acts like loctite or worse.. All need to kinda loose to replace the belt. Seaboard Founder & PresidentLast Post by:
posted: 2 days ago
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6CTA SMX water pump oil seeping
This topic has 1 reply, has 2 voices, and was last updated by
2 days ago August 25, 2025 at 4:58 pm I have a very very minor oil leak from my SMX 1730 water pump. Looks like it’s leaking from the “football” gasket. Can I get away with a new football gasket? The pumps were installed in 2021 this doesn’t look like the shaft seals leaking does it?
Started by:
1 ReplyAugust 26, 2025 at 1:46 pm Shaft weep holes look not to be weeping. Clean everything spic and span and monitor. Rob "Luck is the residue of good design."Last Post by:
posted: 2 days ago
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Oil in after coolers not in plastic bottles
This topic has 1 reply, has 2 voices, and was last updated by
2 days ago August 26, 2025 at 6:55 am I have just completed the Great Loop 640 hrs on my trip. 5.9 BTA Cummins. We were mostly 1250-1500 RPM. When we got the boat we changed to the fwd case breather that Seaboard sells. I am not getting any oil in the catch bottles, however my turbos and after coolers are loaded with oil. Any clue as to why? Also the Aircleaners are soaked. Little and big one.
Started by:
in: Cummins Marine Engines
1 ReplyAugust 26, 2025 at 11:08 am Post good pics of your engine showing everything—————–no close ups—– I want to see it all Usually when you have an issue as you describe, your engine room does not have enough ventilation. Seaboard Founder & PresidentLast Post by:
posted: 2 days ago
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Fuel efficiency of QSB5.9 vs QSB6.7–BSFC
This topic has 16 replies, has 4 voices, and was last updated by
3 days ago
August 21, 2025 at 9:43 am Just bought a new to me trawler, with the 6.7. Had the previous model with the 5.9. The 6.7 is about 10% harder on fuel. I’ve spoken to owners of sister ships, two of them friends and had run side by side, one with the 5.9 and one with the 6.7 and reported similar results. This seems wrong to me, yes it is a tier 3 engine but 10% reduction in fuel efficiency is a lot for a modern diesel. Are the efficiency maps available for the two engine…
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in: Cummins Marine Engines
16 RepliesAugust 25, 2025 at 10:36 pm To ding economy by 10% when running at 50hp would mean the alternator would be using 5 hp, or about 3700W. Alternators are only about 65% efficient so output of 2400W. That’d be 180 amps continuous, not impossible for a really large alternator but unlikely from a 24Si. It will only do 160A stone cold for the first few minutes. I have an externally regulated 28Si, fully instrumented with data logging, and it will do about 120A continuous if…Last Post by:
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Another SmartCraft failure?? Replacement…?
This topic has 5 replies, has 2 voices, and was last updated by
3 days ago August 17, 2025 at 10:52 am 2008 vessel with qsc 540’s, 24v system. Last week, for the first time, I experienced a complete loss of power to the port engine, including shutdown of the Smartcraft display. I believe it is a VesselView 1.5 (I have the PCB serial # if helpful). Since then, it has intermittently worked, and then shut down. Myself and a basic marine electrician believe we have determined the following: Power supply from batteries to engine is providin…
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in: General Discussion
5 RepliesAugust 25, 2025 at 4:03 pm google it–plenty of options Seaboard Founder & PresidentLast Post by:
posted: 3 days ago
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Onan fuel filter gasket
This topic has 0 replies, has 1 voices, and was last updated by 3 days ago
August 25, 2025 at 1:53 pm I have a 2004 Onan MDKAV 9 KW with Kubota D1105. The new fuel water separator filter on the engine is a Baldwin BF1267. They claim it’s a direct replacement for the Onan part number. The filter does not come with a gasket for the center where the filter screws onto the mount. It does have the normal gasket near the outside. The supplier tells me it doesn’t need one but the last one did have a center one like I’m use to on other fuel filte…
Started by:
in: All Other Marine Diesels
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Cummins 6bta 330 overheat
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This topic has 32 replies, has 10 voices, and was last updated by
3 days ago
July 31, 2025 at 2:15 pm My port Cummins 6bta overheats when run over 2200 rpm. The boat runs 160 until I go over 2200 rpm then it takes about one minute to hit 230 degrees. I have done the following trying to fix the issue and I just do not know what to try next. Cleaned – After cooler, Heat Xchanger, Transmission cooler, Installed new 160 degree thermostat, New expansion tank cap, All new hoses including wire reinforced 2″ hoses from the thru hull to str…
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in: Cummins Marine Engines
August 25, 2025 at 10:23 am FWIW, your sea water pump pressures are very close to mine on the CT6A-480s. RG Dodson
32 Replies
Last Post by:
posted: 3 days ago
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5.9 QSB idle suddenly changed after years of consistency
This topic has 2 replies, has 2 voices, and was last updated by
4 days ago
August 22, 2025 at 4:41 am I have twin 380hp QSB 5.9’s in a 36′ Tiara Open, 2006 (2005 engines). The idle has never glitched in my ownership since 2020 (~900 hours then, and now ~1200 hours), and is always at 650 rpm on both engines. I have a low idle switch that drops them to 550 (which is a rough idle) and never use it. After taking on ~170 gallons in a 400 gallon tank, I restarted engines and noticed they were both idling at 620-630 rpm (and the engine sy…
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in: Cummins Marine Engines
2 RepliesAugust 24, 2025 at 5:13 pm Yes, thanks, there’s no question my time is numbered with ~20 year old electronics made in Switzerland, and certainly glad I am not using a 20 year old cell phone or 20 year old computer at home too. I installed two new batteries for the starting side, and other than the starters spinning faster and engines starter faster, no change. However, after leaving the boat, I did start to wonder if Cummins controls one idle set point or two. As m…Last Post by:
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QSC8.3 Aftercooler Fitting
This topic has 4 replies, has 2 voices, and was last updated by
5 days ago
August 23, 2025 at 3:26 pm There is a fitting at the aft end of the aftercooler on my QSC8.3 that looks like a hose barb. It points down and there is no hose on it. Recently I’ve noticed a clear liquid dripping from it after a run. Only a few ounces comes out. Is this an indication of a developing problem? What is the purpose of that fitting?
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in: Cummins Marine Engines
4 RepliesAugust 23, 2025 at 5:35 pm Thanks for explaining what that fitting is for. Now I won’t be worrying about an impending failure. The engines and boat are 2014 and have 730 hours. The boat is kept in fresh water but goes out into Puget Sound several times during the summer. It had been in salt water for 2 weeks when I noticed the puddle after running. It wasn’t hotter or more humid those days, but I was running slower than usual. Earlier runs were at 20Kt a…Last Post by:
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QSM 11 2024 Reman missing a zinc?
This topic has 4 replies, has 3 voices, and was last updated by
6 days ago
August 21, 2025 at 1:29 pm I replaced a 2016 QSM 11 reman with a 2024 Reman last winter. Just had the zincs replaced at 430 hours, to our surprise the pipe leading from the water pump to the after cooler does not have a fitting for a zinc! Huh, is this a redesign and if so why? also, there was nothing left of the zincs after 430 hours! Typically, at the end of the season, I usually had about a third of each zinc left…
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in: Cummins Marine Engines
4 RepliesAugust 22, 2025 at 5:35 pm Tony – just for the record when I repowered I got a new 26 x 23 Acme prop, down 1” of pitch from my old Michigan Wheel 26 x 24. I used to run 20 knots at 1850 RPM burning 18.5 GPH at a 65-68% load. I am now running 20 knots at 1975 RPM burning 18 GPH at a 59-61% load. Anywhere on the rpm curve I’m well below the QSM fuel curve. WOT I’m only at 88% load, lost 1.5 knots but don’t care…Last Post by:
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Using elbows on the seawater cooling side
This topic has 5 replies, has 3 voices, and was last updated by
1 week ago August 17, 2025 at 1:34 pm My diesel guy used straight hose bent 90 degrees when we cleaned all the heat exchanges and replaced the aftercooler. I am doing a fresh water flush in acccordance with the 300 hour maintenance instruction and are really wrestling with removing the hoses. Any issue using elbows sized correctly? Is blue silicone OK? thanks
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in: General Discussion
5 RepliesAugust 20, 2025 at 6:26 pm Identifying your 6BTA Heat Exchanger Seaboard Founder & PresidentLast Post by:
posted: 1 week ago
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ZF/Hurth 630A Marine gear
This topic has 1 reply, has 2 voices, and was last updated by
1 week ago August 20, 2025 at 8:39 am I’m replacing a pair of HURTH 630A Marine gears on a pair of twin Cummins 6BTAs and was interested in the debate as far as using ATF fluid or 10W 40….
Started by:
in: Marine Transmissions
1 ReplyAugust 20, 2025 at 5:57 pm it’s 15W-40………………….I have 4 boats now that have switched over–all reports say the same basic thing– Noticeably better shifting and overall, a quieter smoother operating gear.. Nothing negative. Seaboard Founder & PresidentLast Post by:
posted: 1 week ago
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Galvanic Bonding Wire For 16,000 BTU A/C
This topic has 1 reply, has 2 voices, and was last updated by
1 week ago
August 20, 2025 at 3:31 pm Hi Guys. I need to install Galvanic Protection bonding wires from my A/C units to the grounding board on my Sea Ray 44 Sedan Bridge (QSC). Distances are about 1 @ 15ft, 1 @ 25ft and 1 @35ft to the grounding board. Can you tell me what type and what gauge wire would be best for this application? Thanks in advance. Bobby
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in: Cummins Marine Engines
1 ReplyAugust 20, 2025 at 5:07 pm Virtually all wiring on a boat should be done with marine-grade, tinned, stranded boat wire/cable. I use 8 gauge wire for bonding.Last Post by:
posted: 1 week ago
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Hurth 800 A2 and trolling valves
