# 1997 Mercury 250 efi any problems?



## DavidT (Apr 25, 2008)

Just wondering if there are any major problems with these engines? Looking to get another boat and they have twin 97 mercury efi 250 salt series. how would i check the hours on them?


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## oceansbreeze (May 1, 2009)

<P style="BACKGROUND: white"><SPAN style="FONT-FAMILY: 'Verdana','sans-serif'; FONT-SIZE: 10pt">It may be worth your money to have a shop to do a cylinder leak down test as well as gap test on the Capacitor Discharge Coils. Mercury in the middle 90's made a changeover and the first generation of those coils had problems, general rule of thumb most had the 7mm black plug wires, the newer one have a 8/9mm gray plug wire.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o><P style="BACKGROUND: white"><SPAN style="FONT-FAMILY: 'Verdana','sans-serif'; FONT-SIZE: 10pt">Leak down test is better in my opinion than a compression test. <SPAN style="FONT-FAMILY: 'Verdana','sans-serif'; FONT-SIZE: 10pt">No engine is perfect, and all will have at least some loss. The percentage of air lost should be consistent across cylinders: if only one cylinder has major air loss, then there is a problem specific to that cylinder. Use the following loss percentage numbers as a rough estimate of the overall health of your motor: (again these are just a rule of thumb not written in stone) 

1. Less than 5% - You either did something wrong or have one hell of a nice tight engine.
2. 5% to 10% - Great to good. You should have no worries.
3. 10% to 20% - Your motor may still run ok, but it isn't at it's best. Parts may be starting to wear out....keep an eye on it and test it more regularly.
4. 20% to 30% - It may be (and probably is) time for a rebuild.
5. Greater than 30% - You have some major engine issues that need to be addressed. 

While listening for leaking air on each cylinder, the following guidelines will help identify potential problems. This isn't 100% foolproof, but does give you a good place to start looking for issues.<o></o><P style="MARGIN: 0in 0in 0pt" class=MsoNormal><SPAN style="FONT-FAMILY: 'Verdana','sans-serif'; FONT-SIZE: 10pt"><o></o><P style="BACKGROUND: white"><SPAN style="FONT-FAMILY: 'Verdana','sans-serif'; FONT-SIZE: 10pt">Gap test need to be done to all the coils atthe same timeand not one at a time; mercury coil are not independent of each other since they added the computers. <SPAN style="FONT-FAMILY: 'Verdana','sans-serif'; FONT-SIZE: 10pt">Ref: <SPAN style="FONT-FAMILY: 'Verdana','sans-serif'; FONT-SIZE: 10pt"><SPAN style="COLOR: windowtext">http://www.ebasicpower.com/downloads/cditech/CDI-Troubleshooting_Guide-MERCURY.pdf <o></o>


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## DavidT (Apr 25, 2008)

Thanks ocean breeze. 

Im going to take it for a ride soon but the guy says it purs and has no problems. 400 hours max on them.


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