2001 Mercury 90 hp 2 Stroke

[TnT]

Has anyone had any experience with these motors and what is your opinion of them?

[Barnacle Bill]

Most any Merc is a good motor IF it has been taken care of. If your are contemplating buying a used motor there are a few things you should check first. Check the compression (you don't want to see more than 10% difference in cylinders). Crack the drain plug on the lower unit and let a little oil drain out. (it should not be milky colored). Check the cylinder heads and look for signs of over heating (discoloration or paint peeling). I'm probably leaving something out but its too early for me to think.

[PanMan_VA]

As IBNFSHN said, Mercs are good motors if they have been properly cared for.

I have owned several old Evinrudes and Johnsons and they were great. Only once in many years of fishing did a motor fail to start while on the water (power pack failed, no spark). I have also owned two new Mercs (both four strokes) and have had NO issues with either of them.

If you are thinking about buying a used motor, ask if it was ever used in salt water. If it has been in salt water, remove the engine cowling and check for corrosion.

Pull the spark plugs and make sure they all look about the same. This can be done in parallel with the compression check.

Make sure the engine is pumping water and run it long enough for warm water to come through the prop hub.

[thehines]

I own a 2006 Merc Optimax 90. Runs great, a little loud when running full open.

[Scrapper]

Thumbs up to all that was said. Every manufacturer will produce good and bad engines...just depends on which one you get off the line.

If the engines been around that long...all the bugs should be worked out...and it should be in good shape if taken care of.

As said before...do a compression check....(10% + or -) per cylinder difference...if possible do a leakdown test. If you do both of those you will the information you need on the engine...the leakdown test is actually a better test and will show you more than simply the compression.

I figure its probably fine...but then again...better safe than sorry.

[Scrapper]

Just noticed who I was talking to...lol.

Run it by D&R...they'll do it for you. I could do a compression test for you....but I do not have the stuff for a leakdown test.

This test is down by using compressed air and seeing how quickly the air in the cylinder leaks down...in car engines they'll call it blowby. Each piston will be put at the same posistion with a dial indicator or piston stop...this insures proper readings on each...you will then put the compressed air to it...the gauge will measure the leak down of each cylinder. This will show you if you have stuck rings...coking....or anything else.

One mech on another forum I was reading said

I have been in the outboard repair business for over 15 years and "evaluate" engines almost daily. If I had to choose between a compression check and a leakdown test, I would choose the leakdown test hands down. Both tests are important, but from experience (primarily on 2 strokes) very high percentage blowby or leakdown almost always indicates a serious problem brewing...and I have seen this even with engines that showed normal compression.
Just one example: I had a 1987 Merc 3 cylinder 90hp that ran ok, but was internally noisey to my ear. After running the engine for awhile to get it up to temperature I then checked compression. All cylinders were between 125-130 psi. I then performed a leakdown test. One of the cylinders had over 38% blowby. The others were around 20%.
I then pulled the exhaust cover and divider plate off so that I could examine the pistons visually through the exhaust ports. What did I find? Severely scored piston skirts and partially stuck rings. The cylinder walls were scored as well. The engine was in need of an overhaul, though it still ran. On this particular engine I determined that the engine was badly "coked" with carbon...especially behind the ring lands...this forces the rings out hard against the cylinder walls causing scoring and my guess is the noise was from the excessive scraping. Poor quality oil, or gas or improper engine temp or excessive prop loading were the most likely culprits.
Don't ask me how that engine was able to produce such normal looking compression numbers...I guess at least one ring on each piston was doing something. But that motor was not going to last much longer.
By carefully moving the piston down the cylinder wall while doing a leakdown test you can get an idea if the cylinder is egg shaped and no long round...the guage will show an increase in pressure drop as you get into a bad area in the cylinder. A compression check cannot show that.

He is right by what he says. Don't get me wrong..compression test is great...but you can have compression and still have a high leakdown. Just a little food4thot

[AgriHawg]

Scrapper, you planning on going to Georgia or something?
J

[Scrapper]

Opps...my bad..I saw TNT and was thinking TNT tackle company over in Murfressboro...about 12 miles from me...lol. His handle is something different. :o

[yikess]

I have 2001 90hp Mercury two-stroke and really like it.