What is the difference between the 75hp and 70hp Force motors built in the 90s

[Rickerd]

Hi, I am going to upgrade my 1988 50hp force and am looking at a 1995 70hp force.
What makes the 1995 a 70hp, compared to the 75hp 1996 and up?
I see that the engine displacement is the same as well as the bore stroke.

Also does anyone know how well or if the mounting bracket will line up compared to the old 1988 50hp?

 

[roscoe]

Re: What is the difference between the 75hp and 70hp Force motors built in the 90s

They are pretty much the same at first glance.

But the ignition systems are different.
95 70 used a switchbox ignition (think Mercury thunderbolt from 1980-early 90's.
Also a different carb.

The 75 hp used cdm ignition module ignition, which eliminated the switchbox, but built them into the coils.

There may be some internal porting differences, or timing differences.






There were some other differences on the '99 model, as Merc was trying to use up existing inventory.
The '99 models used a different gearcase, and they used 3 carbs instead of one.


You will find many outboards using the same block, displacement, bore and stroke, that have different hp ratings.
for example.
9.9 and 15 hp
90 hp and 115hp

There are internal differences though.

 

[Frank Acampora]

Re: What is the difference between the 75hp and 70hp Force motors built in the 90s

And neither one will match the existing mounting holes. Either one will make your 50 look sick. They are both hot little engines with surprising performance for an engine using a 10 inch diameter prop.

 

[Rickerd]

Re: What is the difference between the 75hp and 70hp Force motors built in the 90s

As long as it makes my 50 look sick!
How about the mounting bracket, will I be drilling new holes? If so what is the best way to seal the old holes?

 

[Rickerd]

Re: What is the difference between the 75hp and 70hp Force motors built in the 90s

Sorry i just read, And neither one will match the existing mounting holes.
I assume permanent marine sealant.

 

[Frank Acampora]

Re: What is the difference between the 75hp and 70hp Force motors built in the 90s

5200 or RTV silicone will do it. If you are going into wood or glass you can mix up a little resin with old home insulation wet it out well and plug it into the holes. Seal the new bolt holes with again--5200 or Black RTV silicone.

 

[roscoe]

Re: What is the difference between the 75hp and 70hp Force motors built in the 90s

The 70 hp does NOT have a manual release for the power tilt.

I think the 75 hp does.

 

[Rickerd]

Re: What is the difference between the 75hp and 70hp Force motors built in the 90s

Resin and insulation, Good idea!
Thank you for all your advice...

 

[Rickerd]

Re: What is the difference between the 75hp and 70hp Force motors built in the 90s

OK, I haven't found a replacement for my 50hp yet. I have a concern with compression, my book isn't quite clear on it..
What would be considered good compression on the force 70 & 75 motors??? Book, (no more than 15psi variance)
What would compresshion be if it was new or rebuilt??

 

[roscoe]

Re: What is the difference between the 75hp and 70hp Force motors built in the 90s

140-150 psi is excellent

120-140 is good

110-120 still decent