New boat, seeking info

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ctaylor2069

Petty Officer 2nd Class
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Jul 31, 2013
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I just recently purchased a 1985 century polamino. It has the 4 cylinder mercruiser 170. What litre is this motor? I'm looking to diagnose a "no spark"
 
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stonyloam

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3.7 l, 470 engine IF the intake is on the starboard side and the exhaust on the port, should have a heat exchanger on the port side of the engine, and a reservoir with a radiator cap. The most common cause of "no spark" is bad points. Check that you have voltage on the coil + with the key on.
 
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ctaylor2069

Petty Officer 2nd Class
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Jul 31, 2013
Messages
131
Holy crap stonyloam. You some kind of genius or something lol. Like I said I just got the boat know almost nothing about it. I will surely start with the points. I do have power at the plus with hey on. However I also have power at the negative side with key on as well. So that's where my confusion comes into play. Thanks for the info. Keep it coming lol
 
Bt Doctur

Bt Doctur

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put your meter on the neg side of the coil and the other lead to a good ground. crank the motor .if the points are working the needle will jump.
if the needle does not move , the points might be oxidized and not making contact.
 
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ctaylor2069

Petty Officer 2nd Class
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Ok, I currently do not own a multimeter but I will be purchasing one. I cleaned the points and the cap.
 
Bt Doctur

Bt Doctur

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ok then, red neck method
with the points closed insert a matchbook cover between the points. shorting the points should produce a spark.Y N
 
C

ctaylor2069

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Ok I'll give it a try. Once again thank you. Do u know how I can test the coil?
 
Bt Doctur

Bt Doctur

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coils are the last thing because they rarely go bad. In most cases the 1 is points oxidized, incorrecly installed, wire from coil to points broken /grounded
On a mercruiser there is a shift interupt switch that grounds out the neg side of the coil, a third culprit is a shorted tack to kill the spark.
A way to test a coil is to supply 12v to the + side and take a wire from the neg side and "scratch it" on a good ground or the neg post of the battery to produce spark/
 
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ctaylor2069

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Jul 31, 2013
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Thank you doc. I kinda feel stupid. I went out and reset the points. And it fired right up. I hugely appreciate everyone's help. I love this site!!!
 
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stonyloam

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Great C, now that 470 has a iron head and aluminum block, so if you overheat it you can blow the head gasket. You will want to change the impeller in the out drive ASAP, before you take it out on the water. Do that every other year and she should stay cool. Also check for coolant leaking out of the lower starboard weep hole on the engine water pump. There are a couple of seals in there that can go bad. If it is leaking do not try to stop it by plugging the hole, you will need to change the seals, PITA but not too bad. Any questions come on back. Good luck and welcome to the 470 club.
P.S. No genius, just been wrestling with a 470 since "91" LOL!
 
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ctaylor2069

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Jul 31, 2013
Messages
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Well stone I ran into a peculiar situation yesterday. Boat wouldn't start, so I unplugged #1 spark plug wire, to check for spark. And the motor fired right up and ran beautiful. So I hooked back up the wire to the #1 plug. And it started and ran. What would cause that to be?
 
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