Cummins Marine Diesel Repower Specialists Forums Cummins Marine Engines My engines never turn over 1900 rpm in gear

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  • #78985

    Oliver Heringhaus
    Participant
    Vessel Name: Joana
    Engines: 2x 6BT 5.9M 180HP
    Location: Gdanks
    Country: Poland

    Good afternoon together,
    I am since 2 Month the proud owner of a steel yacht build in 1974, repower in 2000 with ZF Transmission and 2 Cummins 6BT 180HP Rated.
    the engines were in the last 11 years never used and made in the years after the repower roughly 400 hours each.
    As i am new to boats in general and Cummins engines as well i have some questions.
    first i start with the most easy one. When we are cruising with the ship with RPMs around 1900 the ship makes 11.2 knots. I cant get the RPMs higher as the Trust levers are touching the Area where they are mounted on, means they are full flat out. If i push them a little more, the engines go on 2000 but the levers always come back. When i am not in gear, the engines rev up to 2.200 rpms but not higher.
    how can i fine tune my throttle wires on the engines? Is there maybe already a topic about it?

    Attached a pic from my boat. i will make tomorrow pics from the different lever positions.

Viewing 6 replies - 1 through 6 (of 6 total)
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  • #79258

    donald roth
    Participant
    Vessel Name: Paumalu
    Engines: Cummins 6BT 180 hp
    Location: where the fish are!
    Country: United States

    If you are getting full travel on the throttle, and are not able to achieve same rpm both in forward gear and in neutral, your vessel is most likely overpropped. (Assuming bottom and running gear are clean)
    This may be intentional, especially on a big, heavy vessel with limited power.
    If the previous owner kept records, you might be able to look up prop specs to verify.

    #79197

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    Do i need these springs connected or can i just leave them out?

    The spring over ride is doing that to protect the pump shaft from being over torqued at full throttle.

    #79196

    Oliver Heringhaus
    Participant
    Vessel Name: Joana
    Engines: 2x 6BT 5.9M 180HP
    Location: Gdanks
    Country: Poland

    fixed, but

    Hey Rob,
    i did as you told and the port side engine did not reach the limiter screw, so i adjusted it. But now if i put both throttles flat out the spring on the pump is strong enough to pull it back by a quarter. Do i need these springs connected or can i just leave them out? If i go to idle on the helm, both levers on the pump get pushed by the controlcables in the idle position with or without the spring.
    thanks, oliver

    #79089

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    The 2,500 is the rated rpm where the advertised HP is produced and it is the MINIMUM rpm for propping purposes. For most engines in this size range for propping purposes you want the engines to hit 3-5% over the rated rpm when the boat is FULLY loaded. For your engines 2,550 is fine IMO. Here’s the 2nd page to the engine data sheet which did not load when I originally attached the 2 page document. The “max” rpm is the high idle maximum and that is a “no-load” rpm (with engine out of gear and at normal operating temperature)

    1 user thanked author for this post.
    #79088

    Oliver Heringhaus
    Participant
    Vessel Name: Joana
    Engines: 2x 6BT 5.9M 180HP
    Location: Gdanks
    Country: Poland

    Thanks

    I will try it out tomorrow. So the chart tells me That the Max rpm of my engines is 2500?

    #79023

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    Operate the pump manually and and be sure it moves easily you are getting full travel and the spring override is working. Then reconnect the throttle cable accordingly and perhaps you need to modify the throttle control at the helm so it has full travel before it’s obstructed.

    Here’s your pump. The limiting screw is the horizontal screw pointing back at the side of the throttle lever.

    https://www.sbmar.com/articles/cummins-6bt-5-9-210-cav-injection-pump-plumbing/

    Attached PDF is your spec sheet with the rated rpm and high idle (no load).

    1 user thanked author for this post.
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