gutless 90 horse

[<angry canuck>]

got aan 88 90 hp that has absolutley no nuts in the bottem end at all. I.ve cleaned all three carbs twice, fuel pump, new lines, ckecked timing , compression up to snuff. what the f#@! ?
motor is on a 15 ft checkmate that used to scream with my old merc 115 on it. I thought this newer yamaha would be at least as good if not better. would incorrect wiring on the dash or control unit cause this or should i just unbolt it and drop it in the drink?

[<Rob>]

Run a 17 inch prop on it.

[<angry canuck>]

hey rob thanks for the reply. I was considering that but the motor will chug and spit at idle and i can feel it in the steering wheel. Also the old merc had a 19 as well as this motor does, so why the huge difference.I spoke with several marinas today and most said it sounds like ignition?, but without seeing it they couldn't help. Just trying to save myself a few hundred bucks in labour by doing the work myself.

[<Rob>]

Ok I own a 115 yamaha 1998 year.
It came with a 17 inch prop. I put a 19 inch
on and it lowered the max rpm to 5300 a 17 makes about 6100 rpms. The motor is only ment to reach about 5500 so watch your rpms.
I fish alot so the 17 makes my boat ***** nice
and slow. I adjusted the low idol screws 1/2 turn
out and it idols mint. 4 carbs on 115 hp.
Parts from this site are priced fair and OEM.
I bought the manual. Only run NGK plugs too.

[<Bazooka Joe>]

I just replaced the 89 88hp Johnson on my 91 Smokercraft aluminum with a new 04 90hp Yamaha 2 stroke. Without a doubt, the Johnson would kick the living snot out of this Yamaha on takeoff. On top end, they are fairly similar.

With a 17p Ballistic stainless, I'm turning about 43-44 mph gps at 5700 rpm. The Yam likes to rev.

So, to your situation, I don't know what year 115 Merc you had. The last 115 Merc I was around was a buddy's 1990 115. There would be absolutely no way this Yam 90 would ever touch that 115 anywhere in the powerband.

Also, you do not want to be doing a straight prop pitch to pitch comparison. You need to know what gear ratio was in the Merc, and at what rpm were you running. Basically, are you pulling the same potential top speed.

On the plus side, the Yam 90 runs very nice, idles great, and barely smokes at all. I just wish it twisted the prop a bit harder down low.

Good luck with it!

[<angry canuck>]

bazooka joe, thanks for you're reply as well. The year of the 115 merc was about 73-74. It was the old in-line six power head,(ya know the ones that were about 10 feet tall) .I just thought that a newer 90 would be the same if not better and be a little more fuel freindly. However i am going to try a 17 '' prop and see. I also only have a speedo and no tach, so i'll have to come up with 400 bucks just to see if will work a little better. I've also been working on an 89 130 v4. So if I can get that on the back end then it'll be yahooo. I will keep you posted. thanks again for the help.

[<Bazooka Joe>]

You don't need to spend for the $400 tach. A plain old Teleflex tach can work. I used the green wire from the control box as the signal. Your year model may have a different color.

[<angry canuck>]

what i men't was 140.00 for genuine yama tach to mach the speedo and 220.00 for the 17 pitch prop plus the good ole 15% tax here in Ontario, Canada. Sorry for any confusion. P.s. Thats 220.00 for a steel prop, not stainless. nice eh!

[<Bazooka Joe>]

Angry Canuck,

OK, I see now. Yes, that would be plenty of $$ to just test out the 90 Yam. If you could get that 130 OMC, it would rip apart either of those two outboards.

Is your boat rated for a 130hp? If so, I could see where the 90 Yam would be a double pooch.

BzJoe

[<angry canuck>]

bz joe

Just got back from the cottage. I found a guy that let me trial run the 17 pitch prop and he also raised my motor two positions higher on the transom. Unbeleivable difference! the hull jumps out of the water quickly and when I start to play with the trim the boat all of the sudden lifts and seems like it is gently rocking on air. Maybe it is, but I'm very happy now. As far as the 130 yami goes....well it didn't pan out in my favour so I walked away, but to answer your question the boat is rated for an 85 hp. I called Checkmate in Ohio and a guy said that provided the transom is still in great shape (it's a '74 hull), that it should hold a 130 but he recommmended upgrading my life insurance policy. However like I said it screems pretty good now and when I really get it to dance it turns around 5800-6000 rpms. Thanks again for all you're help and recommendations. Be sure to keep in touch!

the now HAPPY canuck!

[<Bazooka Joe>]

Happy Canuck,

Glad to hear you've got things working better. With those rpms and a 17P prop, you should be somewheres in the 43-45mph range. I ran a 43.8 with my 17P Ballistic at 5800 rpm the other night.

That's interesting how you describe your boat as floating lightly. My Yam 90 seems to have less influence on the boat than did the 88 Johnson. I don't know if it is a smaller lower unit skag, or what. But, the result is similar- the boat seems to scoot across the water at the same speeds with less aggavation from the outboard.

BTW, not to be a nag, but if your boat is rated for 85hp, you probably wouldn't want to hang 130hp off the back for legal or insurance reasons. If you ever got into a situation with the boat and it was that over-powered, you might be in the hot chair. Canada is probably not as stickler as the US, though. I'm in Minnesota, and while they don't check motor sizes often, IF they did, an over-powered boat is a no-no. Bottom line, though, is that they probably would never check if you are not causing someone to complain.

Good luck with the rig!