Hard or no starting when in water

[alan454]

I have an exasperating problem with my 1989 7.4L Bravo I that will start easily when out of the water on the muffs, but starts very hard or not at all when in the water, particularly when warm. It seems as though the cranking speed has slowed down to about 100-125 RPM over the years but I can find no spec on minimum cranking speed. The engine runs very well after it's started. The batteries are fully charged and the starter is new. Cranking voltage to the starter is in the 10-11 volt range depending on how long I have been cranking. Electrical connections to the starter/ground/bats are all clean. Carburetor is a newly rebuilt Q-jet; ignition system is completely new and heads have a new valve job. Exhaust manifolds and elbows are new, shutters are the new butterfly type (port old-style shutter was completely missing the rubber shell when I replaced it – I assumed it came off in pieces and was expelled, but now I'm not sure??).<br /><br />I can mimic the problem somewhat when on the muffs by intentionally flooding the engine with the accel pump. De-flooding on the muffs works in about 5 seconds using full throttle, but this does not work in water. I noticed this hard start problem developing prior to any work being done; although, it's much worse now. For a bit of possibly relevant history, prior to any of the above work being done I cooked all of the port side exhaust rubber when my port side elbow water passages became clogged.<br /><br />Has any body ever had or heard of a problem like this?

 

[Don S]

Re: Hard or no starting when in water

What exactly is your starting procedures? (throttle position during cranking, how many times you pump the throttle if you do at all, etc. )<br /><br />Has it always had this problem? Does the choke work? I assume yours has the manifold choke coil, it it in good working order?

 

[rodbolt]

Re: Hard or no starting when in water

yes <br /> usually its tracked to a choke or ignition/cranking circuit problem<br /> to properly test the cranking circuits involves a terrible amount more than battery voltage across the batt terminals at cranking.however its incredibly simple.<br /><br /> if I can get it to scan I will send donS a diagram of how to do it, if not I will have to snail mail it to him.<br /> its in a yamaha training manual, most yam techs get glassy eyed looking at it, yet it works for ALL 12v cranking systems from a toro riding mower to a lycoming aircraft engine.<br />I would try to type it now but I am rather heavily medicated, its been a bad 2 days and the guys on DC are gonna love it, .<br /> but lets get back to your issue.<br /> starts good on the trailer with no issues?<br /> ok<br /> does not start in the water? ok<br />the only difference we have as far as the engine is concerned is a moderate increase in ex back pressure.<br />means its capeable of flooding easier.<br />next time do not pump the throttle.<br /> advance the warm up lever at least 1/2 way or maybe more.<br /> try to start it, be aware that engine speed at start up may climb rapidly and react to it. wont hurt anything momentarily but it will scare the jeebers outta ya.<br />it may be as simple as a choke setting to rich or as complicated as an ign sytem failing.<br />keep feeding us details. sometimes the most insignificant detail will set a trained tech that has been bit by about anything that bites in the past 30 years on the right track.

 

[Don S]

Re: Hard or no starting when in water

keep feeding us details. sometimes the most insignificant detail will set a trained tech that has been bit by about anything that bites in the past 30 years on the right track.

Ain't that the turth. So many times a customer (or even a poster here) will say "OH, by the way, don't know if it helps, BUT!" and the hour of troubleshooting is knocked down to a couple of minutes over a minor adjustment.<br />Hope you can get that scanned and emailed rodbolt, I'm curious as to what it is myself.

 

[alan454]

Re: Hard or no starting when in water

DON - my starting procedure is as follows:<br /><br />Cold - two pumps on the throttle, throttle cracked open about 15-25%.<br />warm - throtte open about 10-15%<br /><br />Choke is open when warm and is of the divorced (as I soon will be after spending more time and money on this thing) type on the manifold. This is my second Q-jet since the problem cropped up by the way, rebuilt the first one myself, ordered a newly rebuilt on the second one as I suspected that I may have screwed up the first one.<br /><br />It used to start instantly under any conditions and with any starting procedure. The problems developed over about 20-30 hours of operation and became steadly worse. The boat is now unusable.<br /><br />RODBOLT - I don't pump the throttle when warm but I do advance the throttle once and this is enough for one squirt on the accel pump. However, you did give my an idea - I will try and shut it down about 1/3 throttle and then see if it starts. Still it shouldn't be that sensitive to one squirt. The ignition is a brand new. In fact everything is new in the ignition system now right down to the wires, plugs, and coil. Cranking voltage was tested with one terminal on the starter+ and the other on battery negative. I will move the negative probe near the starter nextime. <br /><br />One detail I didn't mention that I think is interesting is that when I shut it down and imediately crank it will start instantly, if I wait 10 seconds it will start instantly, but if I wait 30 seconds or more it won't start.<br /><br />Is is possible that my old shutter is stuck somewhere in the exhaust and creating backpressure?<br /><br />Thanks for the help guys!

 

[alan454]

Re: Hard or no starting when in water

UPDATE<br /><br />Upgraded 1 battery to a 1000 CCA flooded starting battery and replaced ground cables to blocks, and used fresh fuel. Started in the water easily when COLD this time, ran continuously for 2.5 hours at speeds of 1200 to 4000 RPM with no problems. Had the same no-start problem in water when returned prior to pullout, then started instantly when on the muffs for flushout. Seems flooded when in no start condition. Possibly relevant details discovered this weekend or not mentioned before:<br /><br />- vacuum at idle 12 in-Hg.<br /><br />- timing light on coil wire indicates spark when cranking in the water.<br /><br />- no throttle position would work, never pumped throttle.<br /><br />- lifting outdrive in an attempt to reduce back pressure did not work.<br /><br />- removal of flame arrestor did not work.<br /><br />- gasoline smell in bilge when cranking for more that 10 seconds without pumping throttle.<br /><br />- at 2000 RPM on muffs little or no exhaust felt coming out of prop, most coming out of small outlets above anti-cavitation plate, only water coming out of transom/gimbal holes – is this right?<br /><br />- Carter O-3000 fuel pump was replaced during valve job work with a Carter pump # O-3035 60889 4c228 It looks identical and has vent tube output, salesman said was equivalent to the O-3000. Anybody know the maximum fuel pressure the Q-jet 4MV float valve can handle?<br /><br />- all fuel lines had been replaced with Aeroquip FC234 hose which is braided stainless stuff with a flame resistant blue outer cover (yes it's USCG approved).<br /><br />- input/output ports of Carter fuel pump rotated 180 degrees to facilitate removal of stock hardline and plumbing with FC234.<br /><br />- water temperature is about 165-170 degrees with the 160 deg thermostat.<br /><br />- when replaced intake manifold did not block exhaust crossover ports as I assumed that divorced choke needed this for correct operation. As I recall plates were included in gasket kit that looked like they were for blocking the crossover.<br /><br />Thanks!