little help/ johnson 70hp / mercury 90 hp

[wisemack34]

Ok, i have a johnson 70 hp on my boat, i got a mercury force 90hp...both are 1995..You guys think i will see more power out of the 90 hp to make the change
Ok and i like to ask a couple things..
1. Im looking for a wiring schematics for the mercury force 90 hp so i can the change....
2. Do you guy think i will have to use a whale tale with the 90 hp like i do with the 70 hp..
3. What kind of rpm's im i looking for out of the 90 hp & the max it should be ran at.

 

[roscoe]

Re: little help/ johnson 70hp / mercury 90 hp

Yes you should se more power out of the 90.

1- The only place I know of a schematic, is in a Clymer, Seloc, or factory manual. Pretty basic wiring.

2- How underpowered is your boat?
What rpm are you getting with the Johnson?
Load, hull design, engine height, proper prop pitch, all effect performance.
What make, model, and year boat are you putting it on?
How much gear/people weight do you carry in the boat, not counting the hull or motor?


3- 4750-5250 rpm is recommended at wide open throttle.
I ran mine at 5400 when completely empty, which gave me 5100-5300 under normal running conditions.

 

[WillyBWright]

Re: little help/ johnson 70hp / mercury 90 hp

The Force has 3 bigger pistons. I'd expect better holeshot and higher top-end. Not a ton, but noticable. The wiring wire colors between the two should be mostly common.

 

[steelespike]

Re: little help/ johnson 70hp / mercury 90 hp

Keep in mind that there is no factory support (new production)for Force specific parts.It may share some Mercury parts.I think you will find that 20 extra horses helpful.Your Gallons per hour will be hoger at WOT about 9 gph compared to 7 with the 70hp.But when you throttle back the engine can loaf and still maintain a good cruising speed and better GPH use.
While I have had good luck with doelfins I think something like the Smart tabs is the only way to go.Try to get the best setup before making a decision on smart tabs.
Wnen setting up your motor be sure the anti vent plate is about even with the botton of the boat .Then fine tune the verticle height to the best performance before ventilation becomes a problem.An inch can mean 2 to 3 mph.

 

[wisemack34]

Re: little help/ johnson 70hp / mercury 90 hp

I have a 1995 17' center console Stratus boat. the holeshot is what im looking more for.....so the wiring should be the same on both motor's right......i needed the wiring schematics more for the mercury 90 hp cause the 70 hp is still on my boat...........

 

[roscoe]

Re: little help/ johnson 70hp / mercury 90 hp

Your boat weighs 1400#. The extra hp will be good, but I don't know if it will be enough to satisfy you.
Hopefully it will be enough to get the boat "over the hump" and up on plane a bit quicker.

How much hp is the boat rated for?

 

[wisemack34]

Re: little help/ johnson 70hp / mercury 90 hp

How much hp is the boat rated for?
it says 90 hp max.....is that true...thats what the plate on the console said....
anti vent plate even with the botton of the boat ...is that the bottom where the plug goes in at...cause the 70 hp is above it about 5".........

 

[rickdb1boat]

Re: little help/ johnson 70hp / mercury 90 hp

Sounds like the 70 might be a short shaft if it's that far above the bottom of the hull....

 

[roscoe]

Re: little help/ johnson 70hp / mercury 90 hp

The boat should do well with a 90 on it.

Anti ventilation plate is the large flat horizontal plate located just above the propeller. The motor should be mounted high enough so that the plate is out of the water, when the boat is on plane. This usually means the plate needs to be 1-2 inches above the bottom of the hull.

Go for it.

Tell us how it goes.

 

[ondarvr]

Re: little help/ johnson 70hp / mercury 90 hp

I had a 90 HP force engine, I was amazed at how much fuel it could suck down. I used it for about one season and switched back to my smaller Johnson, the Johnson was more reliable, ran better and used about half the fuel.

Most people don't like Force engines, reliability and parts availability can be the problems. If you already have it, then give it a try, but I wouldn't buy one.

 

[steelespike]

Re: little help/ johnson 70hp / mercury 90 hp

There is a color code chart at brokeboats.com also some wiring diagrams and lots of other helpful stuff.

 

[wisemack34]

Re: little help/ johnson 70hp / mercury 90 hp

well i traded a 1985 35 hp mercury motor....for the 90 hp so i don't think i got much to lose if i try it out...im hoping for a little more hump over the 70 hp i got on it........

 

[Texasmark]

Re: little help/ johnson 70hp / mercury 90 hp

I had an 85 Chrysler 3 cyl on a very light 16' Chrysler boat (1971). I was amazed at how much fuel it could suck down.

My buddies at the time had the new OMC Loopers and they could go twice as far as fast (with their 65 hp engines) as I could on heavier boats (Skeeter and Ranger).

Beins it was West Bend then Chrysler then Force then vaporized.

Mark

 

[wisemack34]

Re: little help/ johnson 70hp / mercury 90 hp

Well guys i got the motor on today...I'll the 70 hp up for a back up...LOL...I got to hook up the controles...and all the wiring......
I think im going to be lost with wiring.
The guy at armstrong told me i should be able to just un-plug one and plug up the other....But...i think he might be a little wrong.......you guys have been so much help it's un-real....
1. the wiring i hope i can handle.
2. the 90 hp came with a 13 pitch prop....do you guys think i should change it..sounds like a lot to me.

 

[Texasmark]

Re: little help/ johnson 70hp / mercury 90 hp

Don't know your gearbox or boat. I have an '02 Merc 90 on a 17' bass boat, aluminum, 3 step pad......as rigged and loaded with my lard arse, batteries and fuel about 1500 lbs total weight, (Picture of the business end is my Avatar at 50 mph (gps)....taken with my cell phone camera....Ha!). I am running a Ballistic 13-1/2 x 24P XP (Extra performance) prop and my gear box ratio os 2.3:1 at an engine rpm of 5900 ( with my new spark plugs compliments of Silvertip); 800 ft mean altitude, 45 degrees ambient temp.

A 13P for a 90 hp is really low. Don't know your gear ratio (very important in getting the correct answer) , but even if it is as low as 2:1 you would have to be pushing a houseboat for a 13 to be the right prop.

My 2c,

Mark

 

[baiwan]

Re: little help/ johnson 70hp / mercury 90 hp

I think you'll get a higher fuel consumption for no extra power.
You'll be asking lots of questions with the change.

 

[JB]

Re: little help/ johnson 70hp / mercury 90 hp

Any particular reason you consider this 2 year old thread active, Baiwan?

 

[Wee Hooker]

Re: little help/ johnson 70hp / mercury 90 hp

Never been a big fan of Force. However, I had a late 80's Johnson 70 that was SWEET. One of my favorite all time motors. Man did that thins sip fuel too!
Not sure I'd make the switch (for another 2-3 mph?) unless I was severly underpowered already.

 

[ziemann]

Re: little help/ johnson 70hp / mercury 90 hp

It's funny how often this happens. Noth'in like raising a dead thread....Somehow, I don't think the advice will help the original poster much any more...

 

[baiwan]

Re: little help/ johnson 70hp / mercury 90 hp

Didn'see the date; I prefer Johnson to Merc - am I wrong?