compression test; my throttle position was neutral would that skew the readings?

[bobbyt679]

compression test; my throttle position was neutral would that skew the readings?

 

[GA_Boater]

Re: compression test; my throttle position was neutral would that skew the readings?

No.

 

[bobbyt679]

Re: compression test; my throttle position was neutral would that skew the readings?

what about warm? I just read a lot of things on google saying that the engine should be run till its warm than remove all plugs and each plug tested one at a time while throttle fully engaged?

 

[bobbyt679]

Re: compression test; my throttle position was neutral would that skew the readings?

and if none of that matters what does 50 50 40 and 25 mean??

 

[GA_Boater]

Re: compression test; my throttle position was neutral would that skew the readings?

Does the motor run? Compression tests can be run on a cold engine, it gets done when the motor won't start. What you're looking for is compression readings to be within 10%. 40 is low and 25 is really low. Try squirting some pre-mix in each cylinder to see if the numbers go up.

Also - Take out all the plugs and ground them. Make sure you spin the motor until the reading stops increasing.

 

[JB]

Re: compression test; my throttle position was neutral would that skew the readings?

PLease don't post multiple threads on one question, Bobby. I will delete your other thread.

Try this way:http://forums.iboats.com/engine-frequently-asked-questions-faq/compression-test-jb-391323.html

 

[bobbyt679]

Re: compression test; my throttle position was neutral would that skew the readings?

sorry jb I am new on this site and was just trying to get answer which seems to be very hard on here lol. I just read your answer and I pretty much did everything you said just my engine was not warm. my motor does run and when it running it runs very strong never dies or anything just when I shut it off and try to restart that is the problem. it sometimes takes 10 mins to get it started. my mechanic who is not a boat mechanic but a 30 year certified Mercedes mechanic told me the compression is bad and to junk the motor and buy a honda! I don't understand it though because like I said when its running it has plenty of power I have had a full load and my boat still gets on plain In no time!!!

 

[bobbyt679]

Re: compression test; my throttle position was neutral would that skew the readings?

pre mix 50 to 1 ratio? my plugs did have some black on them I am starting to think even though my compression numbers are low they are within 10 to 15 of each other and that I have some really backed up carbs and I think my recirc valve possibly could be bad because it seems that whoever had the boat before me had this problem and they moved the red lever on the recirc valve to wide open which it shouldn't be in the wide open position except for choke

 

[bobbyt679]

Re: compression test; my throttle position was neutral would that skew the readings?

and does anyone know where the choke is located on a 1996 spl 112??? I am pretty sure the cable on my oem side mount is broken because when I lift the lever up nothing in the engine moves!!!

 

[GA_Boater]

Re: compression test; my throttle position was neutral would that skew the readings?

Now you're out of my comfort area, I'm a Merc man. I can't help with J/E specific questions. Hope some of the J/E guys will pop in.

 

[F_R]

Re: compression test; my throttle position was neutral would that skew the readings?

Bobby, no way could your motor run halfway decent with the compression numbers you posted. There is something wrong with this picture. And it isn't throttle position either.

 

[glenn property of pam]

Re: compression test; my throttle position was neutral would that skew the readings?

do the compression test again to see if you can repeat the results. You could have a bad o-ring on the compression tester which is causing a bad reading or borrow a diffrent compression tester and try again. anything more than 10% out (not 10 psi) is showing a problem with a cylinder.

 

[glenn property of pam]

Re: compression test; my throttle position was neutral would that skew the readings?

pre mix 50 to 1 ratio? my plugs did have some black on them I am starting to think even though my compression numbers are low they are within 10 to 15 of each other and that I have some really backed up carbs and I think my recirc valve possibly could be bad because it seems that whoever had the boat before me had this problem and they moved the red lever on the recirc valve to wide open which it shouldn't be in the wide open position except for choke

you have a primer with a red lever that is manual or auto (auto being controlled by pushing the key).

 

[bobbyt679]

Re: compression test; my throttle position was neutral would that skew the readings?

So I cleaned the carbs today hoping that was the problem.. Well for the first few mins it wouldn't start than I started messing with the throttle on the engine and when the throttle was high it would start.. Also I had to mess with the re circ valve (red stem) to get it to continue to run... When the re circ valve was wide open I could see fuel coming thru the carbs... When it's running now every 20 to 30 seconds it makes a popping sound like a gun shot. The engine sounds like it wants to run normal but it won't and than a popping sound.. If I move the idle all the way down the engine stalls..

 

[glenn property of pam]

Re: compression test; my throttle position was neutral would that skew the readings?

i have never heard of a re circ valve but then again i have never worked on a 96. What you are calling a re circ sounds like a primer solinoid which is to bypass fuel into the engine to help it start. If the engine requires the choke to be open in manual to run after it is warm then you have a fuel problem and one of the main jets is plugged. You can not open a carb and half clean the carb as plugs have to be removed and the ports cleaned then the plugs replaced. If the engine runs lean it will burn out a piston and you will get low compression. The plugs from the lowest compression cylinder wasnt melted or had any silver build up on it did it?

Go back to basics.....compression test....spark test....carb clean...link and sync

 

[Solittle]

Re: compression test; my throttle position was neutral would that skew the readings?

You are jumping all over the place - First try a different compression gage. If the readings are the same nothing that you can do to any or all of the other components/system is going to make that engine run right. If you get good readings (like around 100 +/-) then methodically troubleshoot using the OEM shop manual. Trying this and that will only mess up things further.

 

[bobbyt679]

Re: compression test; my throttle position was neutral would that skew the readings?

thanks for the advice everyone! yes you are right primer solenoid. when the red lever is fully open I can see the fuel coming back through the carbs. when It is fully open the engine wont start and when it is fully closed it wont start either. as far as fuel I have a new tank and all new lines new fuel water. there was spark and NO there wasn't any silver I only checked the lowest plug for spark and it did have pretty good spark. I am assuming compression is good because it always runs solid sounds good just have had a starting problem.

when I cleaned the carbs I actually removed it from the engine and cleaned both of them with carb cleaner and blew them out with air. than re attached them back on. when I was trying to start it I DID NOT have the air box on. would that make a difference??

I talked to mechanic later this evening and he said everything ive been saying sounds like its going to be a STATOR? does that sound like a possibility??

 

[bobbyt679]

Re: compression test; my throttle position was neutral would that skew the readings?

also when I first got it running it was smoking a lot! and like I said its making a popping sound every 20 to 30 seconds.. the mechanic I spoke to tonight said it was a good thing it was smoking a lot means it is getting oil! didn't answer me why he thought it was popping.. I think I asked him to many questions in a very short time period lol.

 

[bobbyt679]

Re: compression test; my throttle position was neutral would that skew the readings?

I am having a problem getting a mechanic to actually be available and the last guy told me he would be there a certain day and never showed up... I call mechanic shops and they are all telling me 3 weeks before an apt!!! what is going on in florida I cant even pay 90 dollars an hr to a mechanic shop to get my boat repaired asap.. I guess it is a good thing though because I am becoming very familiar with these motors very quickly! thanks for all the help guys

 

[glenn property of pam]

Re: compression test; my throttle position was neutral would that skew the readings?

we can write a list of a hundred things it can be because so far none of the tests you have done seem to be right or the results are wrong. A engine needs spark-fuel-air-compression all at the right time. A outboard is not like a car you have to test all 4 spark plugs for spark as it can loose one and still run then all the unburnt fuel goes into the exhaust and combusts which will cause a loud pop. so again back to basics. test compression with a diffrent gauge and the results have to be repeatable. Test spark with a spark tester the spark has to be bright and snap on all 4 plugs.