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351w Weak crank with spark plugs in, but only sometimes.
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ipokesnails
New User
May 13, 2015, 9:24 PM
Post #1 of 2
(1436 views)
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351w Weak crank with spark plugs in, but only sometimes.
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I recently acquired a free 1974 21' Reinell cabin cruiser with a marinized 1971 Ford 351 Windsor.
The boat had been sitting on land for 8 years without being touched.. After an oil change, some WD-40 in each cylinder, and a replacement starter, it fired up just fine.
Now it sometimes seems quite difficult to crank..
In this video it seemed to turn just fine at first and nearly start, but then it cranks weakly.
https://www.youtube.com/watch?v=FZfsDYQzZ4A
The starter can turn the engine much faster than that, but the battery was getting weak. When it gets like this, even hooking jumper cables to the starter doesn't make a difference.
The engine was even very difficult to crank by hand. Immediately after this video I removed 3 spark plugs to try again; the engine cranked perfectly and started (oops, forgot the unplug the coil)
I put the spark plugs back in, the engine started and ran just fine.
To summarize:
- Old boat engine starts and runs fine after some fiddling and a rebuilt replacement starter
- After sitting for a month, engine cranks weakly, even using jumper cables
- Remove some spark plugs, engine cranks fine
- Replace spark plugs, engine cranks fine
- A few days later, engine cranks weakly
Any thoughts?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 14, 2015, 12:16 AM
Post #2 of 2
(1426 views)
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Re: 351w Weak crank with spark plugs in, but only sometimes.
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OK - sounds like weak battery and or cable connection or even that solenoid which should be a "MARINE" one even though an automotive one will fit and work.
Marinized I doubt totally but doesn't mean it can't work. Marine looks the same but lots is different from all electrical things are spark proof (solenoid, starter, alternator, pumps, blowers etc.) plus marine wouldn't use a nylon cam gear on timing chain or allow any rubber for fuel lines. Fuel pump would have a screw on water separating filter under it not an automotive type. Freeze plugs would be brass, water pump rust proof even though it's a closed system with antifreeze it's ok but will fail without.
Appears to be an "inboard" but same for "I/O = Inboard/outboard or Stern drive) so running this out of water you will burn out the raw intake water impeller in less than a minute if not fed water for exchanger so plan on that if so and wasn't fed water while cranking or running out of water.
Hard to find good real ONE gauge cables and use a strong both deep cycle and starting battery for boats. Specific and may if enclosed could rely on user running a blower to clear out fumes in bilge OR battery have tubes to vent outside of area or you can get one good last explosion from hydrogen gasses venting in a closed area.
It was cranking well once and about sure just that part is poor electrical power delivered to starter. Either battery not up to par which jumping should have worked but most jumper cables are junk and not known how good your jump is unless the cables used can crank engine well without the boat's battery at all and you may want to try that as an iffy battery will suck the power from the jump source first taking available amps down.
Free is great but be sure marine spark control for an enclosed engine is real good as said. A fuel or flammable gas in there is a horror you don't want but wont remember either.
You'll get this to work just be very wary of fuel in closed area like marine does,
T
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