Ski Boat Forum
Repairs and Maintenance => Engine Repair/Maintenance - All Ski Boats => Topic started by: slednw on April 11, 2010, 11:01:57 PM
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So my 1991 Legend starts idles and pulls hard to about 3600 rpms then it cuts out. Not fully but stutters like it is starving for fuel or not getting spark on all cylinders. Boat has 460 hours and looks like the coil is original as it has matching engine paint on it. I am going to start by changing the coil and plugs wires and cap and rotor and see if that helps. I just bought the boat and it looks like it has a fuel water separator. Is that stock? I assume there is a fuel filter some where i should check? What octane should i run?
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Need more info, 1991s were built under the WESMAR ownership days & they used PCM, Indmar, Mercruiser engines. Having just bought the boat the parts you mentioned are always good to replace anyway. Pre & post Wesmar days we did add a spin-on fuel filter water seperator at the plant. If fuel starvation is suppected & everything looks good & checks out I would inspect/change the anti-siphon check valve.
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The serial number on the motor is IF-893395? The owners manual says indmar engine model 250?
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I believe the 250 is the same as in my advance... Ford 351 c.i. / 250 HP :)
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This may be a stupid question but all of my other boats have had outboards. Do I just get parts at auto parts store or is there a better marine product i should be using? I am sure the coil must be marine specific?
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As a general rule electrical and fuel related componets must meet USCG minimum standards. Then it gets a bit confusing, the componets in question are concerned with safety (blowing up your boat) electrical componets such as starters, alternators, bilge pumps, blowers etc. will be "ignition protected" meaning safeguards have been taken & test-proven to resist allowing stray sparks from entering the engine compartment. That said engine ignition componets...spark plugs, plug wires, ign coils, breaker points, etc... are not included. To make it more confusing an engine mfg. may list a MRXXX spark plug to be used & you can only find one that is RXXX (missing the "M" in front) the M stands for Marine which does not have anything to do with USCG stds. It simply means the case is stainless instead of plain steel and is more corrosion resistant which is somewhat irrelevent with ski boats. Having said all this the question of the ign coil remains, Reg 183.440 simply states secondary circuits must meet SAE standards (automotive) AND MOST IMPORTANTLY 183.440-B) STATES YOU MUST HAVE TIGHT FITTING NIPPLES. (not making this up) Here is my opinion for the Ign Coil: Do not exceed the output voltage from the OEM coil by more than 10% and make sure that at least there is an SAE stamp or approval somewhere, (the Chinese Harbor freight types won't have this) but NAPA coils would. OR- when in doubt just ask.....RT
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save the $30 buck for the coil and ensure the fuel line is clean and flowing well
could be the screen @ the pickup in the tank, the water separator, or the screen @ the carb inlet
I've yet to change a coil and have it "fix" something
also it could be your secondaries are not opening correctly
either way good bet she's not getting fuel
Dan T
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I tend to agree my limited experience with motors tells me if you have a spark problem she won't run at all. The fact that the boat runs perfect until i open it up seems to lead me toward fuel issues.
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Well after many hours of fooling around with my boat and searching the internet it is finally running great! The first issue was a vacuum leak on the carburetor. The rear butterfly valves are opened by a vacuum switch which is attached to the rear drive side of the carb. This vacuum switch had come loose causing a loss of pressure. The second problem was some one had used the two float bowl screws to adjust the idle so the boat was running lean at idle. Finally after adjusting the pump arm on the passenger side of the motor I was able to adjust out all hesitation at take off. Now the boat pulls 4200 rpm's which assuming my prop is correct is about right where I should be. So the moral of this story is its probably not your coil!!!!!!!! Boat is running even at aout 165-170 degrees I believe that is right where i should be?
Thanks!!
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FANTASTIC!!! Now... come adjust mine :D Seriously, sounds like you got er running as good as it gets :)
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http://www.ehow.com/how_4854765_tune-fourbarrel-carburetor.html
I just used this as a guide line and it worked pretty good. Can't wait for the weather to get a little nicer so i can put a ski on and enjoy my boat.
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nice job, 600 rpm for nothing, told ya the coil wasn't the problem
assuming your running a 13x13 you may have a 100 rpm or so left on the table
if your running a 13x13.5 or 13 x14 that's all she'll give you
and you may want to pitch down to 13 x 13
next step is tuning the ignition
Dan T
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Yeah I need to check the timing next just need to find a good article on that and go from there.
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Sounds like a lesson on power timing...I haven't done that in 20 years?? go for it Dan
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a lesson it is, and flame job I've received several times from other forums by "real mechanics"
Power Timing is a simple process to extract the most from your ignition on YOUR engine
however you do need to start with a good true baseline, know your running good fuel
have a helper, a good pair of ears, timing light, digital tach, (I also include my handheld GPS), and a wrench
how old are the plugs, wires, cap, rotor, points, if they need replacing ......... replace them
Don't do this b4 your 2nd tank of fresh fuel this season , BAD GAS = BAD TUNE UP
if you don't have all these things or know someone who does, and know how to use them
leave it like it is and enjoy.
Power timing is basically a big NO NO in most applications
because of the potential damage you can create both to the engine and yourself if not really careful
Basically you are adjusting the timing - moving the distributor clockwise or counter clockwise
while the boat is RUNNING, IN GEAR , @ WIDE OPEN THROTTLE............not comfortable with doing that?
Then leave it like it is and enjoy.
with the ignition setup properly to specs (those with points, yuck, dwell, gap, etc)
take your boat out for a spin and get to full operating temp
advise your helper of the process, your helper will either be the
driver or the tuner
you'll need a nice long straight stretch of lake
remove the motor box from the boat
check and adjust your timing per mfgs specs it may be something like 6 degrees BTDC @ 600 rpm
(that's why you need a timing light and a real trusty tach)
adjust the idle speed to specs or your liking
turn the engine off, restart it, is it easy to restart? it should be
if not, fix any other issues
with a sharpie marker mark the distributor flange where it enters the manifold
take the boat out down your straight stretch
determine RPM @ WOT and how she sounds @ WOT with the motor box out of the boat
you should now have a good idle and know your RPM @ WOT as baselines
are you ready?
after you have marked the distributor flange
loosen the retaining bolt just enough to be able to move the distributor by hand with some resistance
get a feel for how your going to sit , kneel, crouch, reach etc over the engine when it's running
fire her up and go for a spin, communication between the driver and tuner are essential
as the tuner will not be paying attention of the driven path........ quirky drivers have the potential
of tossing the tuner out of the boat etc. so make sure the driver knows what and how to do it
take her up to wot - turn the distributor a little one way, while watching your tach and listening to the engine
if it gets slower turn it the other way , one way or the other it will go faster turn the dizzy a little more
do you hear the spark knock, does your driver------- you went TOO FAR turn it back
if you hear knocking you are pre-detonating the fuel and that is BAD!
turn the distributor for max RPM without knock
the amount the distributor is moved or twisted is usually minimal
like not much more if any more than the thickness of the mark you made with your sharpie
so what about 1/16" - 1/8" of an inch(?) not much
have the driver slow down and stop
shut off engine
snug the retaining bolt
try to restart it -------- it may be a little tougher now
if it won't turn over or really fights
take some timing out - turn the distributor back a little (closer to your sharpie mark)
once running reset the idle
recheck the base timing is it more than 4 degrees advanced from the the original base?
they don't like much more the 9-11 @ idle
you may have to do this a few times
you want a good idle 600-750 rpm ish
you want easy starting
after those 2 things then you want max RPM for you engine on your boat
if max RPM means labored starting then you went too far and turn it back a little
we typically see 300-500 rpm increases @ WOT but then there is so much advance
@ idle the engine won't start nicely
by backing it down a little we may see 100-300 RPM gain @ WOT with easy starting
and easy to tune idle and a WHOLE LOT of snort in the middle ------- where you really want it
never overlook overall engine performance just for 1 -2 mph on the top end ,,,,,,,,,, unless your racing
and these boats we're not. however no sense in leaving 1-2 mph @ the dock, find the best overall
happy medium and you'll be set
by the way this procedure only applies to those with old school standard ignitions, with points
or "points eliminator kits"
Those of you with newer boats that have full computer controlled electronic ignitions the above article does not apply
all you have to do is put the engine in "timing mode" set the advance to 10 degrees @ 1000 rpm, set it back to "run mode"
and go skiing
need more?
Call me
Dan T
219-365-1466
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Thanks this is awesome!!!!!!!!!!!!!!!!!!!!
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Waaaaay beyond my mechanical abilities or equipment, but its nice to know you guys know whats to be done if I ever come across a need to do this... Thanks Dan!
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Switched the boat over to a new electronic distributer as the springs on the timing advance on the old one where shot. Was in a pinch and through down for a whole new set up. I really recomend this if you are running on the old points systme it works great.