4 stroke 40 Hp Honda 98 Model compression Results with a closed throttle

[Allen_Aus]

Hi, guys. Im really new to boating. I bought a boat about 7-8 months ago and i didnt touch it since then. I didnt have much time from university exams and assignments. I know that i should have gotten this test done on the purchase and it is too late now. Still just want to know whether it is worth to keep this outboard and get it serviced and tuned. Just dont want to get it serviced and tuned and then blew it.

I just got a compressio test done on it afew days ago in order to see the condition of the outboard before giving it to service. The compression test was done while the throttle is closed. The compression test reslts were 80-90-90. It is a four stroke and as i read on the net, it says that the compression test should be done with wide open throttle.

My question here is what these compression test result of 80-90-90 on my 4 stroke Honda 40 Hp says to you? But as i said the throttle was closed when the compression test was done.

Also would it make difference if the compression was done with wide open throttle? and if it does, how much difference would it make? Anyone has an experience with this?

 

[psteurer]

Re: 4 stroke 40 Hp Honda 98 Model compression Results with a closed throttle

What is most important in a compression test is that all your cylinder readings are within 10% of each other. Your numbers are that. Your numbers are very low for a 4 stroke motor, less than half of what they should be. I would not be overly alarmed. These numbers probably point to an inaccurate compression test gauge and possibly combined with the fact your throttle was not wide open. You are also suppose to do the test on a warmed up motor. Not sure if that was done.

You could do the test again and see what you get. Remember to open the throttle and remove all the spark plugs and then crank it several piston revolutions. I use this inexpensive gauge from Harbor Freight: http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95187