Force 70 to a Force 75 powerhead swap, HELP

[hmantractors]

Hi, all. Removed a bad 1992 force 70 and replaced with a very good 1996 force 75 powerhead. I used all the electrics from the 70 and installed on the 75. My first question is, should this work? My problem is it will not start. It will backfire. So it is out of time. I can disconnect the trigger and in the full range of motion it will only backfire. With a timing lite installed it seems like it is way out of time. Anyone have any experience with this swap? I do not know if the trigger is different between the two other than maybe a molded plug on the end. Would like to solve this on my own before I have to resort to repair shop. Thanks for any possible help. I do not have any electrics for a force 75 to try to resolve problem. Would be willing to buy needed parts if somebody has them.:help:

 

[Frank Acampora]

Re: Force 70 to a Force 75 powerhead swap, HELP

Is it Mercury ignition? If it is Mercury ignition, the stator MUST be installed a certain way. The red Mercury stator is marked as to which direction it is installed on various Mercury and Force engines.

Are you certain that the correct coil wires are attached to the correct terminals on the CD box(es)? And are the correct trigger wires connected together?

The 70 and 75 are essentially the same engine so wiring should be the same for both.

Interesting question: Does the 92 engine use the same lower unit as the 96? In other words, do both have the same crankshaft splines? Did both use Mercury controls or did you need to adapt the 96 to use your 92 controls?

 

[hmantractors]

Re: Force 70 to a Force 75 powerhead swap, HELP

Thanks for your reply Frank. The lower unit is the same. The control hookup for the throttle is different. I removed the tower shaft from the 70 and installed on the 75. The 70 also has a neutral safety switch I wanted to retain. It does have the red Mercury stator. It has been removed and remounted by a previous owner. I failed to mark the location before removing and several holes showed signs of use. I will rotate the stator to get the proper position. Thanks for the heads up. Yes all leads are wired correctly.

 

[hmantractors]

Re: Force 70 to a Force 75 powerhead swap, HELP

I can now give an update. Everything was assemblied as it should be. You can not install the stator wrong as long as the mount on top of the engine is installed correctly. The 50hp engine uses the same parts in a different position. I ended up buying a new quicksilver trigger for the 75hp engine. The color codes are a little different from the 70hp. I have service manuals for both. Crimped new bullet ends on the 70 wiring from the wiring block to snap into the 75 trigger. It is very cold today but it started right up. I now have heard it run finally. Will hook up a water hose and tune when it is warm enough to thaw out the water hose. The trigger on the 70hp worked fine on the 70, I sure thought it would work on the 75hp powerhead. Do not know. It runs now and that makes me happy.

 

[hmantractors]

Re: Force 70 to a Force 75 powerhead swap, HELP

It was 60 degrees yesterday and no rain. Put the muffs on and ran the engine about an hour. All of my tuning pre settings were very close so my fine tuning was very easy. Starts with a light flick of the key, shifts into gear very easy. Rain and snow today, so will have to wait to get on the water. The old 70 had broke rings in the number two cylinder, so only running on two. I feel much better about going on the Ohio river fishing now. I wonder how fast this boat will run on the water now? Hope to find out soon. Be safe all.

 

[hmantractors]

Re: Force 70 to a Force 75 powerhead swap, HELP

:joyous: Finally got on the water today. THIS HAS BEEN ONE BAD WINTER. Engine runs like a dream. On rough water I saw 36MPH. How accurate is the speedo? Taking a week off 2nd week of April to crappie fish, now I know I have a reliable engine to get me there. Got the old 70 completely torn down, as it turns out broke rings in two of the three cylinders. I do not know how it even ran. No issues with the lower unit. All is good!:clap2:

 

[MickLovin]

Re: Force 70 to a Force 75 powerhead swap, HELP

Good work mate

 

[chislechest]

Need some ideas ,have 70 hp with stripped crank can I put a 75 force single powerhead on the 70 hp.The guy selling it cheap great compression fresh water says it wont fit ,but I think it will.

 

[Nordin]

This thread is five years old, please read the roles for this forum and start your own thread.
Do not hi jack a thread.

For information to you, Frank is not with us anymore he has passed away.