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  1. #1

    Question Yanmar 6LP-DTE 250 Turbo V6 Saltwater flow reduction at higher revs.

    Hi all. I'm new here but am in a bind...hoping someone can help me.

    We had our year 2000 engine reconditioned with new rings, valves etc and all coolers overhauled, new turbo and mixing elbow, water pump overhauled/new impeller.

    The engine was running beautifully and has been fine for 15hrs since rebuild. However on the last trip I noticed the temp up 5 degC from normal(77degC norm) at 3400rpm. I increased to maximum continuous revs 3600rpm and within 1min the temp alarm sounded at 90degC. I reduced to 3200rpm and the temp came down fairly quickly to norm.

    The exhaust had a very poor water flow with subsequent throaty sound much more than normal.

    In the Marina at idle the exhaust water flow and sound is normal.

    But when taken to 2500rpm after about 10sec it suddenly changes to reduced flow and throaty sound. Hence a lack of cooling, tripping "C.Water Temp" and "Exhaust" alarms.


    The exhaust viewing window had poor flow. I tightened it in case it was drawing air.

    Thought the impeller was the problem. This was checked and is intact. Strainer at viewing window ok.

    The intakes are clear. The intercooler fine.

    We replaced the old suction hose from intake to viewing window in case it was collapsing.

    All of this done with our Marine engineer.

    Still not resolved.

    Is this difficult to solve or is there an obvious fix?

    Your help is greatly appreciated.
    Thanks!
    Anthony

  2. #2
    Join Date
    Jun 2008
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    Default Re: Yanmar 6LP-DTE 250 Turbo V6 Saltwater flow reduction at higher revs.

    With a name like Hauraki Boaty I suspect you are not far from where I am sitting writing this in Westhaven Marina. There are seals in the raw water pump that could be leaking and letting air in. Has the engineer (who is it by the way?) checked the pump properly or just checked the impeller? You mention a 'strainer' so I assume you are not pulling water through a leg?

  3. #3

    Default Re: Yanmar 6LP-DTE 250 Turbo V6 Saltwater flow reduction at higher revs.

    Hi Aliboy
    thanks for your reply.
    We seem to have resolved the issue. While the pipe from the sea intake to the strainer was replaced, the pipe from the strainer et to the sea pump/impeller wasn’t until the end. This pipe had a massive delamination internally causing closing off at higher revs. I also discovered that these suction hoses are actually exhaust hoses and therefore meant for positive pressure not vacuum. There are no suction hoses in the country of 1 3/4in either so have no choice but to use the same exhaust hose.
    It all seems to be resolved after a trip from Pine Harbour to Islington bay. Engineer was Richard Borthwick.
    Thanks !

  4. #4
    Join Date
    Jun 2008
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    Posts
    553

    Default Re: Yanmar 6LP-DTE 250 Turbo V6 Saltwater flow reduction at higher revs.

    Did you try General Marine in Westhaven for your hose? They carry as big a range as I have found anywhere marine related in Auckland. There is also a pipe place out in West Auckland (name escapes me for now) that is not a marine place but stocks an incredible variety of pipe at great prices.We use them quite a lot and they seem to have almost everything.

  5. #5

    Cool Re: Yanmar 6LP-DTE 250 Turbo V6 Saltwater flow reduction at higher revs.

    Yes went to HDC/HCD and Gen Marine. Both said won’t find
    1 3/4in suction hose in the country

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