Compresion on a 2.4 225??

[Steve2ManyBoats]

Looking at an 81 2.4 225 Merc. Supposedly low hour, fresh water only motor. Looks very clean. Starts and runs on the hose well. Doesn't appear to have been rebuilt. Bores look clean/unscuffed down the plug holes. Can get it with rigging for $1,500. Only concern is compression. Cold compression is 110 psi. across all holes (plugs i and carb butterflies shut.

Even compression is good, but 110 seems low to me. I thought these were higher compression motors. Given it's a chrome bore motor, I'm a little leary of the compression readings.

Quick questions:

1. Is 110 low for this motor?
2. $1,500 a good price for a clean one?

Advice appreciated.

Steve2ManyBoats...

[petehubbell]

Try another guage if you can. Is the battery well charged? Even across all holes is good! That would be a good price in my opinion. PH

[wedge542]

I thought all merc 225 was 3.0, a 2.4 not even a 200 is it or is the older stuff rated like that?

[johnboy 88 vegas]

That motor was rated at the powerhead not the foot.

[tlwjkw]

I thought all merc 225 was 3.0, a 2.4 not even a 200 is it or is the older stuff rated like that?

Dont' think ANY 3 liter stuff started showin' up till early/mid 90's.........

[Steve2ManyBoats]

It's a 1981 motor, 2.4 chrome bore 225 (shaft rated, not prop rated). This motor is billed as having low hours, fresh water only. Looks so under the cowl, but it's a used motor with little background info. Looks very clean, head bolts seem like they've got original paint. Doesn't seem to have been rebuilt.

I checked the compression cold, with a fresh battery and the carb butterflies closed. Compression gauge is known accurate.

Question still is, is it healthy with 110 psi across the board? I thought these motors were in the range or 125 to 130 psi. If it's 110 and should be 130, I'll pass since rebuilding a chrome bore motor is a crap shoot and I don't want to get into having a couple of steel sleeves in a chrome block.

Advice appreciated.

Thanks...Steve2ManyBoats.

[dnelson964]

I checked the compression cold, with a fresh battery and the carb butterflies closed. Compression gauge is known accurate.

Question still is, is it healthy with 110 psi across the board? I thought these motors were in the range or 125 to 130 psi. If it's 110 and should be 130, I'll pass since rebuilding a chrome bore motor is a crap shoot and I don't want to get into having a couple of steel sleeves in a chrome block.

Advice appreciated.

Thanks...Steve2ManyBoats.


Those motors have KEYSTONE rings that will tighten with compression from running. 110 across the board cold sounds good. If you could run it and check it warmed up with throttles open you should well find it closer to 130 across the board.

Even compression cold is the most important reading so I think you have a good motor there.

[T-REX]

Compression kan be decieve'in....Tha even numbers acroos tha board say's all iz GOOD.....110#s IZ low for that mote, should be 120-130#s BUT, will step up with a warm mota, juss like Dnelson said...Also, tha problem wit them ole mota's(actually new ones too), mercury did what ever they had to to sell a mota...If sumbody wanted a blue water mota, they usually had lower compression for sum reason...Never thank your 2.4 iz juss one ov many, I've seen sum reely weird stuff that kame straight from Fon Dulac!!

If ya want tha whole skinny, run a leek down!!:thumbsup:

[donmac]

I'm running twin 81 225's and there 125lbs on all twelve cylinders!

[Steve2ManyBoats]

Cold, throttle plates closed?

[donmac]

cold and plates cracked open, no airboxes!

[gregpro50]

Run a leak down. It is more important that what you are finding is that the cyls are equal. If you got a reading that 5 cyls are 125 and one is 110 then that indicates a problem.

Try another compression guage with the plates open or do a leak down. My 225 ranges from 115-120 and runs like an animal.

A leak down test will give you a definitle answer.

[bigshrimpin]

I've run several of them. 125 to 130 psi what I've seen on these engines. They are tough motors

[gmacrae]

Compression kan be decieve'in....Tha even numbers acroos tha board say's all iz GOOD.....110#s IZ low for that mote, should be 120-130#s BUT, will step up with a warm mota, juss like Dnelson said...Also, tha problem wit them ole mota's(actually new ones too), mercury did what ever they had to to sell a mota...If sumbody wanted a blue water mota, they usually had lower compression for sum reason...Never thank your 2.4 iz juss one ov many, I've seen sum reely weird stuff that kame straight from Fon Dulac!!

If ya want tha whole skinny, run a leek down!!:thumbsup:

This is the advice I'd be following - cold with throttles closed should give you the lowest possible compression figures. The fact they're all perfectly even is great. Other than testing hot with throttles open, you might find the ol girl's rings are all a bit gummed up, and you get another few psi with a good blast of seafoam thru it.