a question for merc people or anyone else

lathehand · #1 10-08-2012, 01:05 PM

I just bought a merc 1986 90hp inline 6 and it happend to have the original installation manual and it also covers the 75 and 115 hp engins.while looking at the prop slection I noticed the WOT on the 90 is only 4500-5000 rpm the others with the same prop and weight boat is 5000-5500 rpm.I did some online searching and discovered the only diffrences in the internal parts of this engins is the carb jets.Next I looked up in my sirvice manual and noticed there were diffrences in the timeing.Now with this being said if I were to rejet and retime my 90 I should be able to push it it up to 115 hp or am I just spitting in the wind.Has anyone out there ever atempted this and what was the outcome.I posted this in a mercury forum but got no replies.Maybe they don't want the truth to sneek out on how they make one motor and make suddle changes to it and call it something else.

spareparts · #2 10-08-2012, 01:18 PM

I'm no tower of power expert, but if you post it up on scream and fly, there will some one along to answer your question. Personally, I'd retard the timing back about two degrees, jet the carb up one size, and go easy on it, they were made for far better gas than the crap we have now.

RidgeRunner · #3 10-08-2012, 03:54 PM

Still fussing with the inlines. What was the last year for those? 1985?

There were some subtle differences between hp, but I am not in the know. Didn't you rebuild one a few years back? How did it work out?

draglink · #4 10-08-2012, 05:58 PM

I just picked up a 115 tower of power for my sons V. I havent messed with it at all yet. They are loved motors around here....and CHEAP!!

spareparts · #5 10-08-2012, 07:16 PM

Quote:

Originally Posted by draglink

I just picked up a 115 tower of power for my sons V. I havent messed with it at all yet. They are loved motors around here....and CHEAP!!

and very light!

smokeonthewater · #6 10-08-2012, 08:20 PM

X2 on what spare said.... if you wanna keep it alive, go easy or buy 110 race gas ($$$$$)

FWIW I recently got a 140 for free but it had a melted piston and a scored cylinder.... I have the stator and complete ignition system tho which was only a few weeks old

Destroyer · #7 10-08-2012, 09:44 PM

Quote:

Originally Posted by spareparts

and very light!

And very skinny...they are the only motor I can think of that might actually fit as twins on a V. Twin 1500's on a V would be sweet. Even a pair of 1150's would be kicka$$....

Union Laker · #8 10-09-2012, 09:09 AM

Quote:

Originally Posted by Destroyer

And very skinny...they are the only motor I can think of that might actually fit as twins on a V. Twin 1500's on a V would be sweet. Even a pair of 1150's would be kicka$$....

Yes nice & skinny twin 115's would be the ticket for a V. They are so light and reliable. I used to have a 115 on my 19 Wellcraft Cuddy we just run good premium & keep her a little rich side on the oil. Smokless Lucas 40 to 1 Usually 1 Quart to 10 gallons then add a pint of octane boost to every tank, there would be no need to retard it unless you here a little ping upon acceleration. The compression is around 150 - 155 all the way down dry.

90 115 & 150 were all the same dont tell anyone, Just fuel differences .

lathehand · #9 10-09-2012, 11:08 AM

Yep Ridge still messing with the tower of power for all the reasons mentioned plus I can here the sound of them across the lake it's like music to me.The only reason I'm wondering about the possiabilty of bumping it up is I need to replace my 1977 merc1500 witch is original to my v.The old thunderbolt ignition needs to rebuitl and I can't find parts anymore.I gave a guy $100. for the 90hp with a bad lower. Turned out to be the pinion gear. Got a new gear for $150.I'm not realy into speed anymore and the 25 to 30 mph would be fine for me. But pulling the grandkids around tubeing and skiying isn't going to work. So weather or not anyone has heard of trying to rejet and retime a 90 I'll try a befor and after. All I got to loose is the $250 I got into it.The boating season is slowly comeing to a end around here so other than rerigging it may be spring when i can do some lake testing.

Union Laker · #10 10-09-2012, 11:19 AM

Pull the Jets & use the next letter size on the existing jets. should get at least 10% more power out of her. I have a little 800 Merc on my 19' Starcraft & kinda miss the 3rd tall person in the boat. Love the inline 6.

Grew up on Lake st. Clair & the fastest boats were the 16 DONZI w/ 383 Holmam & Moody. But the 16 Check mate would walk anyone with the
Merc 150, Across the flats they scream. Pull your arms off skiiing.
Man that was back in the 70's Am I really that old.

What ya got Red Stripe or Blue stripe? on your 90.