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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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    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
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    8,203

    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...

  5. #5

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

    Update: I pulled the engine and took off drive. Turned over by hand and was easy to turn. Drained the fresh oil out the pan since I could get all the oil out now. Not a spec of metal or debris. Thinking not a spun bearing. Also took the started off the good engine and swapped them. Put engine back in boat and doing the same thing - barely turning over.

    With the starter from the bad engine the other engine starts right up. So not the starter. I did test voltage at hot side of starter solenoid on both. Both engines have 12.5V before starting. Good engine drops to 10V when cranking and starts right up. Bad engines drops to 8V and barely turns. Thinking this is problem. Something is causing some serious draw. But when not pressing starting button, voltage remains constant. Does this mean something wrong with starting switch?

    Thanks

  6. #6
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    8,203

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

    I'd put my money on a bad cable or dirty connection....so you need to make sure the positive and negative current paths are intact.

    I would use the voltage drop method to find the culprit. plenty already written out on the www.

    Another 'easy' check that sometimes work is to use an IR temp gun at each connection. The bad connections will get hot when starting current passes thru them...

  7. #7

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

    Turned out to be the battery selector switch. By-passed switch and fired up! Have slight ticking sound, so going to check valve adjustment, but at least it starts up good now.

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