1997 90 HP Mercury-Good engine or bad?

[nightstalker]

I'm looking at a 17' Key West CC with a 1997, 3 cylinder, carburated, Mercury outboard. Nothing on the cowling except Mercury, 90 HP. I don't see any other designations. Does anyone know anything about this engine? I don't think it's an Optibomb, but then again, this engine is foreign to me. I'm supposed to have a sea trial on Sat. along with a compression test. What would be good compression on this 11 year old engine? Can anyone tell me if it's a reliable engine or a money pit.
Nightstalker.

 

[tashasdaddy]

Re: 1997 90 HP Mercury-Good engine or bad?

along as it is a fresh water motor, there are no bad mainstream motors. they all have there quirks. the maintenance is the main thing. compression above 100 and within 10 % of each other.

call seller and get serial number and ask which motor it is, and post it.

 

[achris]

Re: 1997 90 HP Mercury-Good engine or bad?

Those engines are very reliable. My brother has the same year as that. The only problems he's had were the stator (replaced under warranty) and a dry throttle pivot bolt (didn't allow full throttle). The only thing you should know is that they are very rough idlers. They give great fuel economy and are dead simple to work on.

Chris............

 

[DJ]

Re: 1997 90 HP Mercury-Good engine or bad?

Those engines are very reliable. My brother has the same year as that. The only problems he's had were the stator (replaced under warranty) and a dry throttle pivot bolt (didn't allow full throttle). The only thing you should know is that they are very rough idlers. They give great fuel economy and are dead simple to work on.

Chris............

The 3 cyl. 90's did have a bit of a reputation for a rough idle. However, that would not stop me from buying one.

Do a search, on this board (Merc. Area). I believe someone posted a procedure to re-jet them and they idle a lot better.

Update!

I found one article on the subject. It appears to deal with idle adjustments, rather than rejetting. See below.

http://forums.iboats.com/showthread.php?t=225241&highlight=rough+idle+mercury

 

[nightstalker]

Re: 1997 90 HP Mercury-Good engine or bad?

Thanks for the help guys, but it's a dead issue. I was able to take it for a sea trial this morning and I said forget it. The motor ran poorly and would not get above 4500 RPM's. When it came time for the compression test, his tester was broken, mine was not. The compression was 112, 108 and 85. I said forget it.
Nightstalker

 

[Silvertip]

Re: 1997 90 HP Mercury-Good engine or bad?

I have a 75 HP version of that motor and I would not consider it a "rough" idler except slightly off-idle. This is a big displacement 3 cylinder so it will not idle as smooth as say a four or six cylinder motor. It is not objectionable at all in my view and is a very reliable motor.

 

[DJ]

Re: 1997 90 HP Mercury-Good engine or bad?

Thanks for the help guys, but it's a dead issue. I was able to take it for a sea trial this morning and I said forget it. The motor ran poorly and would not get above 4500 RPM's. When it came time for the compression test, his tester was broken, mine was not. The compression was 112, 108 and 85. I said forget it.
Nightstalker

Good show! You did your homework and it $aved you.


Silvertip,

I also have a 75 2S. You're right, the 75's do not have that issue.

 

[boatmanjf]

Re: 1997 90 HP Mercury-Good engine or bad?

Hey, you can't go bad with that engine. Infact the powerhead is made for mercury by Yamaha. I have had a 93 for years. The rough idle can be fixed by increasing the idle jet on top carb by 2 stages. I didn't think it was a problem but did it any way. Engine runs great. These motors are a little cold blooded and like the choke for the first few minutes, but thay love to run WOT. Good buy and have fun.

p.s. Never had to rebuild this engine. Still have 125psi comprestion.

 

[Texasmark]

Re: 1997 90 HP Mercury-Good engine or bad?

If anyone is still tuned into this........I have the 90 and I think the reliability, performance, and economy are super. On the idle thing, there are two things: large diameter cylinders and loop charging adding to the "rough idle". Course the old OMC alternate firing twins weren't all that smooth.

I've had mine 2 years now, used 2 years when purchased, and have changed plugs (type) and had one CDM go bad due to a cold temp non-working problem...$72 to fix that. Other than that have done nothing but routine maint. I did open the carb low speed jets 1/4 turn because of hesitation on hole shot with my 24P prop (pretty good load getting up with that......but then.........).

The rough idle really shows up with heavy,high pitched, props, but just up the throttle a few 100 and it goes away.....and it's not all that rough at idle. However, after having a tower anything is rough......well, son's V6 is smooth but it's a looper and my tower was a direct charged cross flow.

Mark