Mariner 90 hp question

[Capnbly]

Hey folks,

I just joined the forum, read a few posts here and I have to say that as usual on these forums, we have some pretty knowledgeable people on here. Thanks for being here.

I have a question about the outboard motor on my pontoon. It's a 1989 90 hp Mariner and it has given me pretty good service. But this past summer, I noticed that when I power up on it, the RPM's will go up, but (without a tach) I can tell it's not running to full potential.

If I run it about 3/4 throttle (or even full throttle for that matter), it will go like that for a while, then it's like something "breaks through" and it powers on up the way it should. As long as I leave it up there it runs at full strength, but if I back it down, then power up again, it will go back to running at the reduced rpm's until it decides it wants to run at full strength again.

There's no set pattern to this either. It's kind of hit and miss.
My first instinct is that it's a carb problem, but I am by no means an outboard mechanic. I have not tried running any Seafoam or equivalent through it yet, but I'm thinking of trying that first.

Any suggestions from y'all would be most appreciated.

Thanks,
Kris

 

[CharlieB]

Re: Mariner 90 hp question

Troubleshooting an intermittant problem needs to be done in a methodical manner to prevent spending money on unnecessary parts.

A compression tester, a spark tester set to 7/16, and a DVA meter are three highly recommended tools to solving a motor problem.

Verify compression on all cyls are within 10% of each other. This determines the motor mechanical integrity.

Test spark on each cyl. This verifys the ignition system is capable of starting the motor.

Download, read, the Outboard Ignition Troubleshooting Guide from CDIElectronics. This manual will walk you through the DVA tests necessary to verify the high speed capability of the ignition.

Once Compression and ignition are confirmed the only thing left is the fuel system.

Download the corrct service mannual from

http://forums.iboats.com/showthread.php?t=309079&p=2072211#post2072211

This mannual will direct your testing, cleaning, and adjustment of the fuel system.

Repost any problems and we will help clarify and direct your next steps.

 

[1nebel0]

Re: Mariner 90 hp question

After you do the above, you most likely have a carb problem...very common given our great gas these days...Buy a cheap rebuild kit and clean them out and do the lync and sync... I just purchased for $49 from Harbor Freight an Ultrasonic cleaner that worked wonders on my 200h.p carbs.. I rebuild them every couple of years given the gas we have.. it cheap insurance that I am not going down during the upcoming season...Cost me $45 in three kits and I know I won't burn the motor up from running lean on a given cylinder...Good Luck

 

[MickLovin]

Also check your spark plugs, they are even easier to check for how your motor is running.

 

[enginepower]

I'm sure this issue is fixed by now.....post is 3 years old.....