*** 1986 Mariner 135hp V6 compression 90 psi??

I just bought this moor and did a compression check after running it for about 10 minutes.

The compression in all 6 cylinders was 90 psi, I know that its good in a way cause the readings are all within 10% of eachother but how far are these readings from factory spec? I just want something to go off of and I know it wont be near factory spec if its never been rebuilt.

Please if someone knows mercs/mariners please let me know.

thanks!

Re: *** 1986 Mariner 135hp V6 compression 90 psi??

I have a '86 150 HP V6 Mercury. I did a compression test last night on all 6 cylinders. First I tested them cold, 90-95 psi on all 6. Then tested them all after running engine. Exact same compression readings, ranging from 90psi to 95psi. Warm or cold made no difference. I could not find the exact range (from mfg) that I should be expecting. SELOC manual just mentions they should all be within 15 to 20 psi of each other. Hope that helps.

Re: *** 1986 Mariner 135hp V6 compression 90 psi??

thanks for your reply, Im just wondering how the motors work as to if v6/s have lower compression than say 90hp or 115hp 4 cylinder motors. I have a 73 115hp Evinrude that has 135 psi in all 4 cylinders.

Im planning on selling this mariner motor as i want to stick with evinrude as I have evinrude/johnson controls already, so my point is when I try to sell it to someone and they see the 90 psi readings I want some better knowledge on my side just in case someone tries to make me think my motor is not that good...

Re: *** 1986 Mariner 135hp V6 compression 90 psi??

Well if someone looking to buy it tells you that 90 psi is a low compression, then tell him/her to show you where it states that. If he can show you, then you found the actual specs from the mfg you've been looking for. Just a thought. I was disappointed that my $28 SELOC manual did not state my compression. Or perhaps it does & I have not found it yet. Good luck.

Re: *** 1986 Mariner 135hp V6 compression 90 psi??

90 lbs is low....should be a minimum of 110-125........while the motor will run fine it will not have the power it should have and the value goes down as a rebuild is in its future...Do a leak down to really know the condition of the rings.......no guessing then.....

Re: *** 1986 Mariner 135hp V6 compression 90 psi??

One thing to consider with ALL of 'em reading low (motor could be just worn out though) is tha guage. Tha only way to get tha true readings is with a KNOWN gauge, as in one that reads right on a known compression motor..........Rented, Harbor Freight, cheapo's and etc. are tha worse.............And if 90lbs is right its low period. Don't need a manual ta say its so.........On tha bright side is that if its right there is probably no damage ta anything. Maybe just wore out rings or rings that have lost their tension. A slight hone and new rings may bring it back ta life. But it still needs ta be taken down and pistons, cylinders checked............

Re: *** 1986 Mariner 135hp V6 compression 90 psi??

I am using a cheap gauge but I did use this same gauge on my 73 115hp Evinrude that read 135psi in all cylinders (give or take a few psi).
But this mariner fires right up, it does smoke a bit and was thinking about decarbing it but I'm afraid that the carbon build up (if there is any) would be filling an gaps with in the motor.

I will see if my neighbor has a better one.

Also how long should I let the motor run for to warm up to be sufficient to do an accurate compression check?

Re: *** 1986 Mariner 135hp V6 compression 90 psi??

Hot or cold won't make much difference. We check ours as soon as we bolt tha geads on with tha power head settin' on bench without carbs and/or efi bolted on. There is very little difference on steel sleeve motors after we get it done and runnin'. I wouldn't do a thing to it as for decarbin'. Tha low comp will only show as a power loss. Tha motor will seem ta run fine. It can really go unnoticed by most till it gets really low. It will just slowly lose its get-it.............