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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 14169
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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What would be a good compression reading on a 1986 350 magnum

Customer Question

What would be a good compression reading on a 1986 350 magnum mercruiser with about 500 hours? I came out with readings of 110, 110, 115, 115, 115, 115, 115, and 120.
Submitted: 5 months ago.
Category: Boat
Expert:  Jason replied 5 months ago.
Hi Jerry, my name is ***** ***** I will be helping you today. The specification is 100 psi or better, anything below that and the engine is considered worn out, and there are no guarantees of how it will run. That being said, those numbers are low. You might get 1 or 2 seasons out of it, but that's about it. A used but healthy motor would read 140 to 160 psi in all the cylinders, a like new engine would be 180+ or better. The only thing you might want to do is retest it with another gauge to see if those numbers are accurate. If you used a good gauge like a Snap On brand, then the numbers will be accurate, if you used a harbor freight cheapie gauge there is a 50/50 chance the numbers are not accurate. Did you have any other questions on the issue?-Jason
Expert:  Jason replied 5 months ago.
I think that should do it. But I work for tips so I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.Questions do not close out, so if you have to come back later on with follow up questions to the issue you still can even after doing a rating.Thank youJason
Expert:  Jason replied 5 months ago.
Hi Jerry, was there anything else?
Expert:  Jason replied 5 months ago.
It looks like you read my reply without putting through a rating for me. Please keep in mind the website does charge you to speak with me, but they will hold your money and not credit me for helping you out if no rating is put through. If you have a problem with the ratings box or can not see it please let me know.ThanksJason
Expert:  Jason replied 5 months ago.
Hi Jerry, just checking in. No rating has been put through for my service yet, did you have any other questions on the issue?

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