1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what next

[treeguyus]

90 HP Mercury two cycle compression is good but reliable mechanic tells me has a air leak (air leak test). Mechanic tells me it is good until it reaches the top. He doesn't have a bore scope!!! Does it need to be overhauled?The engine idles very well and the idle is set at lower then mfg specs, top end is always good and starts very well.

Mechanic thinks I shouldn't do anything now, considering how well it is running.....what do you guys think

I like to keep the motor as it is a perfect match for a Lund 1890 Pro V and I like the torgue it has for back trolling and out of the hole.

 

[carholme]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

Does this reliable mechanic tell you where the leak is? If the compression is good, what was the reading? And what is good until it reaches the top? An engine that starts and runs well throughout is not a first place candidate for overhaul.

The idle on that engine should be 600-700rpm in the water, in gear, What is your idle rpm?

What is your engine s/n and do you have the service manual?

Gerry

 

[treeguyus]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

Let me correct a couple of facts: It is a 1994 pulled off memory thinking it was a 1998 sorry.

Serial # 1F10213SDOh00624

Readings taken at top of dead center of the stroke:your

Cylinder #1 25%
Cylinder #2 30%
Cylinder #3 40%

9% leak until at the top then the above. Compression is 150#'s

Idle speed is set at 500 RPM slow for fishing.

thanks he thinks the reason it is running good is the cylinder is good until the top.

I appreciate your thoughts Gary

Does this reliable mechanic tell you where the leak is? If the compression is good, what was the reading? And what is good until it reaches the top? An engine that starts and runs well throughout is not a first place candidate for overhaul.

The idle on that engine should be 600-700rpm in the water, in gear, What is your idle rpm?

What is your engine s/n and do you have the service manual?

Gerry

 

[carholme]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

1F10213SDOh00624

1F10213SD is a model number which brings up a 1996 Mercury 9.9 hp, 4 stroke, not a 90 2 stroke.

0H00624 is the right format for a s/n but it is missing one number after H and I wonder if the H should be a G.

Really need to get these numbers correct so we know what we have.

Gerry

 

[sam am I]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

http://forums.iboats.com/non-repair...-call-good-leak-down-test-results-371681.html

Agree w rodbolt's leakdown numbers, these are ideal of course. I had 1992 w 90'ish PSI in a cylinder that had like 90% leakage, scuffed up pretty bad. Other cylinders that were slighty scuffed were in the 40-50's but, think most of that leakage was due to normal wear.

I never mic'd it though but, the scuffing in those cylinders was JUST starting down low towards the exhaust bores. Motor probably would have ran a few more seasons though.

Your numbers sound about right though for guess work and assumed age. With age of course, the cylinders tend to ovulate, errrrrr ummm.....ovate more towards the top sides hence, most leakage at TDC.

I guess those numbers could be a combo of ovation and/or mild scuffing.

Have the mech pull the head and see, not too difficult to do, two stroke head is more or less just a plate.

If it's scuffing up, it's a crap shoot eh? but, i'd personally rebuild....If it's just normal wear (oval'ing/tapering, mic it or visually, you'll tend to see the cross hashing marks in areas and as you rotate around the bore, no hashing marks) run it!!

 

[wired247]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

If it was mine and it was running good I wouldnt touch it.

 

[carholme]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

Exactly!

Gerry

 

[Faztbullet]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

Unless you mechanic has a very very good leak down tester dont worry about it. I doubt the numberare close as the compression stated is way to high for that engine. If it runs fine leave it alone. A side note is all standard 2 stroke will have a close to a 6-8% leakdown and air supply must be constant...

 

[treeguyus]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

Will get the correct number when I pick up the boat. For some reason wrong numbers recorded

1F10213SDOh00624

1F10213SD is a model number which brings up a 1996 Mercury 9.9 hp, 4 stroke, not a 90 2 stroke.

0H00624 is the right format for a s/n but it is missing one number after H and I wonder if the H should be a G.

Really need to get these numbers correct so we know what we have.

Gerry

 

[treeguyus]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

I am told that the 1994 2 cycle 90 hp has higher compression numbers when compared to the newer 90 hp 2 cycles is that true

Unless you mechanic has a very very good leak down tester dont worry about it. I doubt the numberare close as the compression stated is way to high for that engine. If it runs fine leave it alone. A side note is all standard 2 stroke will have a close to a 6-8% leakdown and air supply must be constant...

 

[CharlieB]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

150 compression

WOT fine

Idle fine

Move along, nothing to do here.

Next

 

[James R]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

Nice one Charlie B.

 

[treeguyus]

Re: 1998 Mercury 90HP Two Cycle Engine Air Leak Test. Mechanic Says It Leaks what nex

I want to keep the weight low as possible on the transom of my boat. So at some point I will have to overhaul this one or go to a 90HP etec or sell the boat and get one that is wider at the water line for the weight of the 4 stroke. My 90 HP two cycle weighs 288#, as compared to an etec, at 320# or a fourstroke around 360#. Particularly for back trolling