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  • Weird Acceleration

    I am having a issue with cool engine response to applied throttle. Engine in my 1994 Sea Sport with a Volvo Penta 290 DP has been running great except when starting out after not running for a couple of hours, ie. after trolling for a few hours with kicker motor. Engine is a 5.0 Ford 302. Fresh rebuild.
    When main engine throttle is applied when wanting to take off, the response is non existent. The engine is running, comes up to about 1200-1500 RPM, throttle manipulation does nothing to increase speed, and then it just stays there until it decides to take off and then it jumps up to wherever the throttle position is set. From that point on it is fine. Subsequent take offs from low idle speed is as should be with no issues.
    I wonder if there is a electric choke issue or something else. My wife says it just needs to warm up a lot before it decides to go. Not the ideal situation as sometimes there is a need to start up and get moving immediately.
    This issue combined with a spun prop (now fixed) made me think I had a problem with a clutch cone. This seems all about carburation. What do you think?
    Attached Files

  • #2
    Has this a problem started started since the engine was rebuilt? Was the carburetor also rebuilt at the same time?
    Is your kicker engine a 4 stroke and are you drawing fuel from the same fuel line that feeds the main engine?
    Kenner, Louisiana 1980 Donzi 18'. 2+3 6.2 MPI Alpha 1

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    • #3
      This is a new problem that has started since the rebuild. It is another bug to work out along the way. Yes the carburetor was rebuilt by an old guy who is famous in the racing world for his carb work. The fuel to the kicker comes from the same 55 gallon tank but there are 2 factory installed pick-up ports in it. The fuel for the kicker goes to it’s own inline filter before entering the fuel injection system of the kicker motor which has never skipped a beat.
      It seems like the last three times out i have had this problem. Someone, (a plumber) suggested that perhaps the throttle cable is gummed up and is not moving the linkage, but is stretching in the cable jacket and the releasing. That is possible but it doesn’t fit the other symptoms very well. Like why would the same thing not occur when the engine warmed up real good.
      Thanks for your help.

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      • #4
        Start the engine on a flush out with the flame arrestor removed. The electric choke should start to open as soon as the engine starts and be fully open within 2 minutes. The choke thermostat just might be set too tight or the heating element is either burned out or there is no voltage to the choke housing. Look at the ground wire also.
        Kenner, Louisiana 1980 Donzi 18'. 2+3 6.2 MPI Alpha 1

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        • #5
          Thank you. Love low cost repairs. I think i will contact my rebuilder. It was $300.

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          • #6
            my guess is it is also the choke, however the choke pull-off should open it. when running with the choke closed, it would be running rich.

            reading the plugs would help determine this.

            other ideas.....the anti-siphon valve is stuck, and the kicker is pulling fuel back from the main engine. then the motor is struggling with what is left in the bowl until it can re-fill its supply. while its doing this, it would be running lean. again, reading the plugs would help.

            or the carb still has issues and should be taken back apart and have all the passages cleaned (and verified clean by probing each passage with fishing line or a fine wire.)
            Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

            1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

            Past Boats
            1970 Wooster Hellion - Merc 9.8
            2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
            1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

            What’s behind you doesn’t matter.Enzo Ferrari

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            • #7
              Thanks Scott Danforth. The anti siphon valve was The rebuilders first guess. He was very decent about it and refused to take any money for his hour and a half of tinkering with the carb. He found a little corrosion in the float bowl, and set the jets to where there should be. I had one turned out too far. Other than that he commented that the places were dry that would have indicated anti siphon issues. I haven’t had a chance to get in the water yet. I will update you after that.

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              • #8
                Just a shot in the dark, possible fuel pump low pressure at idle speed until carb fills up with enough fuel. my first guess was also anti siphon valve, but that was ruled out.
                1995 wellcraft martinique
                mbsports boss 210
                1998sea doo gtx

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                • #9
                  My 1994 Sea Sport, 19 foot with a 302 Ford is still being weird on Acceleration. I have written on this topic before but maybe have a little more data to describe the issue. I am experiencing a prolonged period of time in which this engine just will not come up to power until it is good and ready and wants too. After it wants to it is fine. Today, the in the water start up went fine. There was a little dying and needing to be restarted a couple times then she settled in and ran fine at about 750-900 RPM. When she warmed up enough to stay running (about 5-7 minutes) we left the dock. At our launch site there is a 5 mph no wake zone for about a mile and then you can open her up. Except that when you throttle up from 12-15K it only goes up to 2000 rpm and just stays there. That is not enough to get up out of the hole so i have learned to back off a bit and just wait. After a couple of minutes of this low speed, without touching the throttle lever, suddenly she just speeds up and I pull the throttle back and off we go running at 3200-4000 RPM and it works just fine. Subsequent stops and starts are not similarly affected until after a prolonged period of cooling while trolling with kicker motor and main engine not running.
                  I have a 55 gallon tank with two separate factory pick-ups for fuel. The kicker is a 9..9 Tahatsu with its own fuel line and filter and the only common link with the main engine is the full fuel tank. I would suspect some sort of weird siphon phenomenon except the symptoms don’t occur only after use of kicker. Wondering if the accelerator cable is to blame somehow but it seems to operate the carb linkage just fine,

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                  • #10
                    If a motor suddenly pick up speed you would look at ignition issues.-----Run with timing light on each lead and see how spark is behaving.-----Also check / inspect fuel pump diaphragm.----Replace float / float valve in the carburetor.

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                    • #11
                      The Centrifugal Advance Mechanism might be sticking

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                      • #12
                        Merged
                        Money spent @ Boat Restoration should be measured in Smiles & Pride SHOP IBOATS-BOAT SPECS-FORUM HELP-REPAIR/RESTO

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                        • #13
                          Originally posted by Dandydan View Post
                          My 1994 Sea Sport, 19 foot with a 302 Ford is still being weird on Acceleration. I have written on this topic before but maybe have a little more data to describe the issue. I am experiencing a prolonged period of time in which this engine just will not come up to power until it is good and ready and wants too. After it wants to it is fine. Today, the in the water start up went fine. There was a little dying and needing to be restarted a couple times then she settled in and ran fine at about 750-900 RPM. When she warmed up enough to stay running (about 5-7 minutes) we left the dock. At our launch site there is a 5 mph no wake zone for about a mile and then you can open her up. Except that when you throttle up from 12-15K it only goes up to 2000 rpm and just stays there. That is not enough to get up out of the hole so i have learned to back off a bit and just wait. After a couple of minutes of this low speed, without touching the throttle lever, suddenly she just speeds up and I pull the throttle back and off we go running at 3200-4000 RPM and it works just fine. Subsequent stops and starts are not similarly affected until after a prolonged period of cooling while trolling with kicker motor and main engine not running.
                          I have a 55 gallon tank with two separate factory pick-ups for fuel. The kicker is a 9..9 Tahatsu with its own fuel line and filter and the only common link with the main engine is the full fuel tank. I would suspect some sort of weird siphon phenomenon except the symptoms don’t occur only after use of kicker. Wondering if the accelerator cable is to blame somehow but it seems to operate the carb linkage just fine,
                          disconnect and plug the kicker then try it.
                          Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                          1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                          Past Boats
                          1970 Wooster Hellion - Merc 9.8
                          2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                          1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                          What’s behind you doesn’t matter.Enzo Ferrari

                          Comment


                          • #14
                            Although it may not be an issue, I haven't read where the vent from the fuel tank has been checked for blockage. Unless I missed it. Just something to check.
                            If ya can't fix it with a hammer,ya got yourself an electrical problem.

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                            • #15
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                              Thanks for all the in-put. I do have a brand new 2-3 gallon tank that came with the kicker. I have never used it (still in box) so it should be easy enough to try and see if the same thing happens when I only use the kicker hooked up to that little tank and the the other line disconnected and the pick-up plugged off. Otherwise how does a timing light hooked to the 2-8 plug wires help? Am i just looking to see if everything is firing? The vent from fuel tank? Where would that bad boy be? There are the ones that allow air out when dumping gas in, but are there others that allow air in? I’ll be checking for that. It could be fuel pump diaphragm though it is a new pump with the engine rebuild so with as much trouble as it is to get down to the mechanical pump, I’ll save that for later. Could be a faulty float or float valve but I’ll have to have my carburetor expert check that out. No one thought the cable could be the cause so i won’t worry about that for now. I did just remember that the little fuel filter seems to get a lot of stuff pretty quick. Maybe I’ll start with a changing of that. It is easy and I have a spare on board. No gas getting in, boat not gonna go good!

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