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  1. #1

    Default 1977 Chris Craft Twin Inboards turning over hard and running labored.

    I have a 1977 Chris Craft Sportsman 25' fiberglass boat. Has twin GM 181 FL Marine Power Engines with 2bbl Rochester carbs. According to my research, Chris Craft built these engines using a standard 3.0L block...could be wrong though. Have the old Paragon gears. Port engine has just over 500 hours and the starboard has about 650 hours. Last summer had boat out pulling a tuber and when stopped the switched riders, starboard engine would not start up very easy. Turned over really hard and draw must have been quite high on battery, because would almost stall the other engine. Finally did start, but ran like it was under extreme load- no more tubing. Limped it back to the dock. Got it started one more time that summer and it barely started and at idle it felt like there was high resistance somewhere. Also noticed there was water dripping out near bottom of bell housing...popped soft plug, may be an unrelated problem.

    Things I have checked:

    • Took out all 4 plugs and turned over (thinking maybe water on top of cylinder due to old leaking copper head gasket). No water shot out and did not turn over any easier.
    • Checked compression. All within 10 psi of 150.
    • Starter rebuilt season before and was working great. Fairly confident it is not this.
    • Changed oil and filter. Cut filter looking for metal shavings indicating a spun bearing, but filter was clean. I did notice the oil had some gas in it and level was high. Replaced oil and filter and no change in how it turned over.
    • On the note of gas in oil- I rebuilt the old carter style fuel pump thinking bad diaphragm- no holes on inspection, but put back on when oil was changed.


    Looking for any suggestions on what to try next. Is it time to pull and rebuild?

    Thanks!

  2. #2
    Join Date
    Sep 2008
    Location
    Maryland - USA
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    8,177

    Default Re: 1977 Chris Craft Twin Inboards turning over hard and running labored.

    may be the gasoline washed one or more bearings....an oil analysis on what was in the sump may have been revealing but that opportunity is gone.

    I'd suggest comparing the effort needed to turn over each engine, by hand, with the plugs out...if the starboard is noticeably tighter than the port, its likely time to pull it out. If its bad, i would start planning on doing the other engine as its possible to experience the same situation. Not having a detailed history makes all of this pure speculation....

    May want to have the gears gone thru while the engine is out...and swap the damper plate if it's loosened up at all...

  3. #3

    Default Re: 1977 Chris Craft Twin Inboards turning over hard and running labored.

    Hi Makomark

    Thank you for the suggestions. I do still have the oil from the sump. What would I be looking for in the analysis?

    I will try to turn over by hand later today. Also, could the gears be bound up?

    Thanks

  4. #4
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    8,177

    Default Re: 1977 Chris Craft Twin Inboards turning over hard and running labored.

    The lab that does the analysis will scan the oil and tell you what they found and the likely source(s)....Blackstone is one of the leaders and you can check their www site for more info. they can also give their opinion on using the oil after it has sat for however long it has been...

    If you are asking about the reversing gears being the cause, its possible but I can't say that I've seen it.

    Another option would be to get one of the cheaper 'borescopes' that are available from the big online sources...they typically have a USB connector and use your phone or laptop as the display...using it, you can pull the plugs and inspect the cylinder bores and look under the valve cover (to some extent) without any major disassembly....you may be able to borrow one as well...

    If they are original engines, being over 40 years old, I'd say an overhaul wouldn't hurt....especially if you don't have the full history on them...

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