battery too strong for comp test? that possible?

[hullofalottatrouble]

so my boat battery needs replaced id say.. doesnt hold charge long enough to do even one good cylinder.. so if i say run some jumpers from my car battery to boat battery and do the comp test like that.. is that ok? i am sure the readings are affected on the low end due to low battery strength but can they be affected on the high end as well? <br /><br />might be a stupid question but just want to make sure.. <br /><br />thanks..

 

[180shabah]

Re: battery too strong for comp test? that possible?

Get a good strong battery IN the boat for a compression test.

 

[hullofalottatrouble]

Re: battery too strong for comp test? that possible?

yeah i intend to.. but still have the question out of curiosity.. would that setup result in questionably high comp results for some reason?

 

[fisherman73]

Re: battery too strong for comp test? that possible?

The technically correct way to perform a compression test is with a jumper battery connected and throttle blades held fully open. <br />so to answer your question no you can not have too much battery, only too little would effect the result.

 

[Reel Poor]

Re: battery too strong for comp test? that possible?

And ALL the spark plugs out.

 

[rbezdon]

Re: battery too strong for comp test? that possible?

A jumper battery from your car will NOT be as strong as a good abttery IN the boat. This is due to the long jumper cables. Even the most expensive super heavy duty ones are not as good as a fresh battery IN the boat. An I agree with Fishermen73, no way to get too much battery for a compression test.

 

[hullofalottatrouble]

Re: battery too strong for comp test? that possible?

okay thanks everybody.. forum has been a great benefit to a new boat guy like me..<br /><br />so far have used the forum to diagnose and fix my bad shift cable.. fix my drive trim pump.. fix my overheat problem "i think".. run a comp test to test if I have any serious damage from overheat situation..<br /><br />so thanks everybody

 

[Don S]

Re: battery too strong for comp test? that possible?

Here is the "Technically Correct" way to do a compression test on an engine, and there is nothing there about using jumper cables.<br /><br /> http://www.boatfix.com/merc/Bullet/97/97_25.pdf <br /><br />Water in a cylinder could give higher compression.

 

[hullofalottatrouble]

Re: battery too strong for comp test? that possible?

Don,<br /><br />Thats what I followed.. Just dont have the fully charged battery to do it with.. Actually needed to jump start the boat just to get it running not just for the test..