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    Topic
  • #34816

    cory shears
    Participant
    Vessel Name: Shear Bliss
    Engines: 2
    Location: Tacoma, WA
    Country: United States

    New member…Thank you for the add.

    1988 Bayliner 38’ Hino 175s (N/A’s) with 21×19 4 blades. We cruise at 1850-1900 rpm 8.5-9 kts). If I am 2+ hours into an excursion, I will see soot off the port-side hull exhaust. The port side has house batteries, start batts and dinghy’ 25 hp outboard. Fuel consumption for both engines is great, temps fine, etc. K&N air filters-clean.

    RPM at max is about 2800. Mechanic checked injector 2 years ago, rebuilding 1. Still soot. We bought the boat 4 years ago and first year was no problem. Now, constant problem. Someone recommended the slip stream isn’t allowing engine to breathe so exhaust is sticking to hull.

    I have oil analysis done each year and get an ‘A’ grade. I just changed out the Trans coolers this spring (old ones weren’t in bad shape and had little blockage).

    2600 hours

    Any recommendations?

    Thanks!

Viewing 9 replies - 1 through 9 (of 9 total)
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  • #35276

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    If it matters, I’m on Phil’s side as to additives………..

    Remember, “There are some diesel additives that claim to help that??…………………………………CLAIM is a very big word when it comes to products along these lines..

    Tony

    #35272

    cory shears
    Participant
    Vessel Name: Shear Bliss
    Engines: 2
    Location: Tacoma, WA
    Country: United States

    Once again…..thank you for the response. I always learn something from this site, especially in my short tenure. I am getting a better understanding/handle on these engines and hope to keep them in the 10,000 hr category.

    Thanks again.

    #35244

    Philip
    Participant
    Vessel Name: 2007 35’ Cabo ‘FUGA’
    Engines: Cummins QSC8.3-540’s
    Location: Long Beach, CA

    I usually recommend the ‘less is more’ theory when it comes to fuel treatments. Unless you have a specific identified deficiency with the fuel I recommend staying away from ‘treatments’ as the tend to cause more issues than they solve and they are money wasted.

    Now your issue is soot, which I unburned fuel. Ask yourself if any treatment will help burn the fuel? Assuming you have fresh fuel then the answer is nope….

    #35241

    cory shears
    Participant
    Vessel Name: Shear Bliss
    Engines: 2
    Location: Tacoma, WA
    Country: United States

    How do we feel about fuel additive (injector cleaner)? Might this help with soot problem or are they all just snake oil?

    #35240

    cory shears
    Participant
    Vessel Name: Shear Bliss
    Engines: 2
    Location: Tacoma, WA
    Country: United States

    Thank you very much!

    #35232

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    If your 175 HP engines reach 2800 RPM and you cruise at 1850 or so, you are asking very little of your engine — Maybe 45 HP each / 2.5 GPH per engine on a 3.0 Exponent prop curve, maybe less……..

    They should go well over 10,000++ hours if “Marine Age” or a coolant system failure does not take them out.. They are not going to just wear out.

    Running them up to 2500 or so for a few minutes once in a while will keep things clean..

    From a long time ago:

    Low Speed Running & “Break-In” of Marine Diesels

    Nothing has changed !

    Tony

    #35202

    cory shears
    Participant
    Vessel Name: Shear Bliss
    Engines: 2
    Location: Tacoma, WA
    Country: United States

    Thank you both for the reply. Clark, my engines are 175 hp, 6 cylinder (N/A).

    I usually run them at 1850 rpm (8 kts). I can accept the nature of the beast and will continue to monitor. Love my Hinos and will maintain them.

    Any problem running them at my posted RPM? I run them up hard at the end of a trip to, what I think is ‘cleaning’ them out (or what my dad used to say in his old car; “just cleaning out the carbon”).

    Thank you both again!

    #35199

    Clark Leighs
    Participant

    What is the specific model of the engines? When looking up the specs I see the ones I can find are 3,000 rpm rated but with turbos. Is yours rated at 2800 or 3000 rpm. The N/a units I see are lower HP and 2800 but need it confirmed. 4 cylinder or 6 cylinder?

    Does it make rated rpm by a digital tachometer, not the dash tachs? E bay for ~ $20 for a laser pointer digital phototachometer. Get one, use it, as you may not be running at the revs you think you are and that might be part of the problem.

    One reason you may be seeing more black soot now vs several years ago is the weight of the boat has increased whether you realize it or not. That may mean the props are no longer quite right for present operating conditions.
    The other I can note is your choice of boat speed. Not being run at either displacement speed or at planing speed. You may be putting the hull at a trying to climb over the hump speed which will put increased load on the engine without it getting the air it needs to support that level of fueling.

    Back off the throttle a bit and see what happens. You may find that backing off a bit produces a lot less smoke.

    THe next time the boat is out have the props checked at a shop for any tweaks or damage and consider having some pitch removed. Even if you run at the same boat speed the engine will rev more taking in more air for a cleaner burn and less per cylinder firing load.

    Tony has far more experience than I but I have been through something like this. I agree about the engine age being a factor as mine is even older but a lot has to do with how you run and set it up.

    The one big difference between our boats is I have a dry stack and I could SEE the difference immediately after my prop. downpitching. Same boat speed but less smoke because at that same boat speed my engine ran 150 -200 rpm faster yet still well withing its capabilites at less loading per firing. Just more firings. The engine burned cleaner. Now I just run slower.

    At your indicated cruise rpm you could easily run up another 100 or 200 revs to keep the boat speed although I think that is part of the problem. You can however make life easier for the engines.

    Hope this makes sense.

    #35061

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    Cory,

    Although you may not like my reply, this is what I conclude based on what you have posted…

    1) You have 30 year old diesels and the technology that was built into them from that vintage. Simple engine, simple fuel systems and ZERO emission standards, including something that is called PM (particular matter)…………………….You are running them well within their rated power range and you have is what is known as soot in the exhaust gases..It’s part of burning diesel in engines of that era and design.

    2) Also, you probably have what they call a “Station Wagon” effect going on where the diesel exhaust tends to hang at the transom or outlet, and the soot which is present in the exhaust gases “sticks to the hull”……

    Solutions? There are some diesel additives that claim to help that?? Other than that, be 100% sure your engines are getting as much air as they can “suck” with no restriction what so ever…

    Tony

Viewing 9 replies - 1 through 9 (of 9 total)

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