getting a 90 HP I-6 Merc. tell me about them

[ScottSabre72]

My father-in-law is giving me a strong running '84 90HP 6 cyl. Merc with power T and T. I have always had Johnson outboards but I am truly excited. The 90 Merc feels far more powerful than my 70HP Johnny. His boat ran 53 MPH and mine should run at least 40-45 with the Merc. Plus I love the air raid siren sound of the 90 and 115 Mercs. What can you tell me about them, what should I be careful of and look for? I do plan on getting a Seloc Manual for it. Can't wait to do the transplant!!! Can the throttle arm be switched to the other side of the control box like OMC? His boat is side console and mine is center console. Thanks

 

[andrewkafp]

Re: getting a 90 HP I-6 Merc. tell me about them

Look for corrosion/water around the plugs. Could be signs of head water cover failure. Then you have to remove the cover and replace gasket. This usually results in shearing off bolts and subsequent removal of powerhead for re-drill. Don't get me wrong.. It may never happen, but I read that it's common on 70's 80's Mercs. Also, keep the carbs clean and use fresh fuel to minimise "Lean" operation, as this can burn pistons. Other than that, people seem to like them. You may see some negativity here, as it's a Merc problem forum.. So you won't see to many praises.. only complaints.

 

[ScottSabre72]

Re: getting a 90 HP I-6 Merc. tell me about them

What about the control box? Can I move the throttle arm to the other side of the case?

 

[catmania]

Re: getting a 90 HP I-6 Merc. tell me about them

Pretty good motor, mine is a 95 and i went from a 70 Johnson to the 95 merc, BIG difference!<br />Change the impellar every season, use a higher octane fuel (midgrade or above)use a nice 45:1 mix with a good marine 2 stroke oil. Keep the fuel clean, maybe have the carbs rebuilt or cleaned if you find any gas leaking from them when starting. Ensure to grease the pivot between the transom mount and the leg (prone to seizing). Use a good strong battery (they like a hot spark). Get a tach and a water pressure indicator, mount them in a highly visible location on the dash and keep an eye on them. I think your max revs are around 5200 the manual should let you know for sure. Water pressure should be 4-12 pounds. Get in, hold on, let 'er rip

 

[Merc90HPnewbie]

Re: getting a 90 HP I-6 Merc. tell me about them

I've got an 85 90HP straight six. I would greatly recommend getting the Mercury manual. I ordered one from them, it was a little expensive but worth it. watch that tell tale and buy a pump kit now so you have it to install later on at the first sign of trouble. I have the Seloc and the Mercury manual, as well as the Mercury owner's manual and the parts guide. The mercury website is good for Identifying parts also. If you need any info or pictures let me know, I will try to help.<br /><br />Oh and take my advice with a grain of salt as I've only owned a boat for one season! ;-)

 

[Bobby Powell]

Re: getting a 90 HP I-6 Merc. tell me about them

Hello,<br />I have a 1986 90hp IL6 Mercury. I have to say that I really do like this motor. Except for the few power pack issues I had early on(I bought some used ones), this motor has been reliable and strong. I have it mounted on a 1986 21' Wellcraft V20 hull. I know the hull is way underpowered but this motor takes it to 36 mph and cruises good at around 28-30mph. I plan on repowering sometime but I have a hard time with forking over the money when the motor performs so well.<br /><br />One thing I have noticed is if you let it sit up for a month or more it is really hard to get started. Starting her up once a week keeps her happy and keeps the fish on the table.<br /><br />Definitly take the advice about replacing the water pump once a year. I let mine go for about 5 seasons and had it fail on me out in the bay. That was a long, long day.<br /><br />I'm no mechanic but I just wanted to post some positive info.<br />Good luck with your new motor.<br /><br />Tight Lines,<br />Bobby

 

[ScottSabre72]

Re: getting a 90 HP I-6 Merc. tell me about them

Thanks guys, I am going to take it out a few more times with the Johnny. I am almost finished with the fiberglass work and am dying to go fishing. Then it will be time to put the Merc on. Good to hear that Mercury supports its owners on its website. Johnson/ Evinrude only promote their new motors and their friggin lubes.