2001 Mercury 2-stroke 90 - what to look for?

[longshanks]

Hi guys

I've found a sweet looking 2001 ELPTO Mercury 90 2-stroke that appears to be in good shape, used mostly in fresh water and well maintained. The seller claims it's had a recent water pump replacement, T-stat, leg oil, and fuel filters. Compression is said to be even on all three at 120psi. He figures at around 100 hours on it, but there is no meter. It was used in a twin-engine application, and he's already sold the other motor. The only kicker is that I need to buy my own controls, he's selling the motor only.

He has agreed to start the motor up for me and do a compression test, and I plan to look it over carefully. I understand that these are reliable motors, but without being able to run it through it's full rpms I'm not sure if I'll get a clear indication if there is anything wrong with it.

Any suggestions on what I might look for/ask?

thanks for your help

 

[Silvertip]

Re: 2001 Mercury 2-stroke 90 - what to look for?

black, three cylinders, 2.34:1 gears, oil injection, and that it runs. Since it is not on a boat you obviously can't do an on water test so you have to be satisfied with the compression test (provided he hasn't loaded up the cylinders with oil in an attempt to boost compression). Trim and Tilt should work via the button on the side of the motor. With engine off and in neutral, spin prop by hand. No roughness allowed. Prop in good shape? Check all engine bolts for evidence of wrenches being applied. If paint is missing, wonder why?

 

[4JawChuck]

Re: 2001 Mercury 2-stroke 90 - what to look for?

Look at the starter and ring gear for worn or missing teeth, the starter on these engines is rubber mounted and has issues. The starters have no drain hole in the base so they tend to collect condensation inside until they short the brushes and won't turn the motor over, if you buy it I suggest you take the starter motor apart and check it and drill a drain hole in the bottom casting....hopefully it won't be corroded inside.

Carbs should be checked for scum inside, there is a brass drain plug on the bowl which will let you see inside the main jet for debris, pull them and have a look or just get used to the idea they should be taken off and cleaned.

The timing linkage is all plastic connectors which are crap, even new they have excessive play. Replace them and lubricate with silicone grease to take up the play and retime the engine...makes a huge difference to the idle quality and running characteristics.

I have a 2003 75/90HP and these are the problems I found even though it ran good when I got it. After fixing all these little issues it purrs and starts instantly. BTW set the idle mixture identical across all three carbs, the manual suggest setting the top carb 1/4 turn in from the others but I found it idles better with them all set the same.

 

[longshanks]

Re: 2001 Mercury 2-stroke 90 - what to look for?

thanks a bunch for the information you guys.

is there any place on the motor that the gear ratio is stamped? I'm not sure what this one is.

Also - What are acceptable compression #'s for this motor? Seller indicated that it reads 120 on all cylinders, which seems ok to me. I think this motor reads around 150-155 as new, so if there has been a ~30psi reduction in compression, is this an indication that the motor has been well used?

Is there any way to see if the motor knocks, without running it under load? I've heard of motors idling well, and compression being ok, but they knock under load. Is this something I should even be thinking about?

Based on the motor's history, I expect that it may have been run hard over it's short life, but aside from replacing a poppit valve, it never needed any work other than regular maintenance and winterizing.

thanks again. Going to look at it this week.

 

[4JawChuck]

Re: 2001 Mercury 2-stroke 90 - what to look for?

Gear ratio is 2.33:1, stock compression numbers are around 120 psi so its in good shape...mine reads 123psi on all three but my gauge reads a little high.

Rod knock can be a concern but you would be able to hear it with a stethoscope at idle, ideally taking the motor out for a run or in a water tank is the best but sitting in the driveway on the muffs should be enough to hear any problems.

If you decide to buy pull the prop (if your getting it with one), and check for fishing line wrapped around the output shaft, anything on the shaft can get under the seal and wreck it or allow water into the lower which would be bad.

No matter what the seller says I would drain the gearcase and check the oil for water intrusion. Flush with new fluid and refill so you will know its clean and dry, after your next trip recheck the oil by pulling the lower plug and look for water (oil floats so its the first thing thats going to come out). Don't be fooled by a milky appearing gear case oil as it gets aerated in use, drain a little into a small cup and let it sit...the water will settle out and it will be obvious.

These little 3 cylinders aren't known for being the smoothest idling engines out there but after tuning mine is smooth as glass and doesn't shake even down to 600 rpm, part of the issue is the top cylinder idle mixture being a 1/4 turn in from the factory causing it to run a little lean at idle. Make all the carbs the same and it idles smoothly.

The reason for the 1/4 turn in on the top carb is for better starting characteristics but I haven't noticed any issue with mine, it starts like a top and doesn't flood. A good way to test your idle mixture setting is try and start the motor with a rope on the flywheel when its warm, it should start easily with no throttle manipulation or choking when its warm.

BTW the choke is actuated by pushing in the key on the throttle or by pushing the little black button on the fuel solenoid mounted on the engine under the cowl, its near the flywheel so you can't miss it.

Good luck with your purchase.

 

[longshanks]

Re: 2001 Mercury 2-stroke 90 - what to look for?

geez 4Jaw, it sounds as if it would just be easier if you'd sell me your motor

OR, I could continue to look for one that I can actually test on the water.... This is the only part of the deal that I'm concerned about.

The lower end looks brand new on this thing, and I am going to carefully check it over. I am going to try and check for rod end play using a screwdriver, if the guy will let me. Hopefully if compression comes out good, and there is no end play, and the motor looks good, I'll be ready to spend some $$.

does yours beep when you turn the key to start it?

and do you have any guesses on what prop it should spin on a #1500 aluminum 15' boat, plus a couple passengers? I think he has either a 17p or a 19p for it, my pick.

 

[4JawChuck]

Re: 2001 Mercury 2-stroke 90 - what to look for?

I run a 22" Laser II prop on my 16' Tuffy, she moves out at close to 50 mph with just me in it.

BTW you have a PM.