Hooking up jump box to starter 1987 force 85 to diagnose

gram404

Cadet
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Apr 4, 2022
Messages
12
Hi there,

I am going to check out a new to me 1987 force 85 to replace mine. The motor has no hookups ( gasoline, steering, electrical leads) and it is sitting on a saw horse. I would like to be able to turn the motor over to confirm that I have spark, a working starter and compression test.

What is the best place to tie in jumper cables from a battery or jump box?
 

Jiggz

Captain
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Oct 23, 2009
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3,817
Caution, make sure all bare wires are taped off and not cross connected to each other before attempting the following:

Presuming no electrical hook up meaning the ignition switch connections and T&T wiring not connected, you can still check all three, i.e. spark, starter and compression. You will need remote starter which is basically nothing but a two pole (On/Off) switch and of course a battery. For the battery, if there are no large red and black cables on the motor (for battery connection, if there are battery cables then connect them to the battery), you can just use jumper cables. Connect the positive to the solenoid main terminal and the black to ground. Connect the remote starter across the solenoid coil terminals (two small terminals). Remove all spark plugs and ground the plug wires and insert/thread in a compression gauge. By simply pushing down the remote starter the starter should engage and crank over the motor to give you compression readings.

If you do not have a remote starter, you can still check starter and compression by directly jumping the starter, positive to the starter terminal and black/negative to ground. This will activate the starter and hopefully crank over the motor to get compression readings.

You can also do simultaneously the spark test. If the shut down wire (white wire from the engine terminal board) is disconnected (just make sure it is not touching ground or better yet tape it off), which it should since there's no ignition switch wired, you should also see sparks from the plugs if you have a spark tester connected to the plug wires.

Since there's no fuel connection you might want to bring in a oiler of some kind to oil the cylinders through the plug holes before cranking it over. Even spray can fogging oil will do.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,307
most jump packs are only to assist the main battery. you may not have enough CCAs to crank the motor fast enough
 

gram404

Cadet
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Apr 4, 2022
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12
Great thanks for both responses! The remote starter is a great call and I hadn’t thought of using fogging spray!
 

jerryjerry05

Supreme Mariner
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May 7, 2008
Messages
17,924
I just bought a new jump box.$85 from Amazon
It's 8x5x3 (aprox) with various attachments.
It is amazing the power it has.
Enough oomph to cold start a Ford diesel with dead batteries.
 

gram404

Cadet
Joined
Apr 4, 2022
Messages
12
Also another quick question. My boat and motor (1987 force 85) currently have power trim. The motor I’m looking to buy (88 force 85) has no controls with it including the trim. Should I expect to have any mating issues when I do the motor swap—obviously I’d like to keep the trim system on the boat.

Also, I bought this from Amazon to lift the motors. Have people had good success with using this?

Thanks
 

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Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
Unfortunately, the flywheel lift kit you bought does not fit your 85HP motor. The kit you bought will fit those smaller and older Force/Mercury motors with threaded center flywheels. The later models and larger HP motors don't have threaded center flywheel instead has three bolt holes for removing the flywheel. The same holes can also be used to lift the motor. Just make sure you use high grade bolts, i.e. Grade 5 or 8. There's however a special tool to lift the powerhead which threads to the crankshaft end but I doubt it's still available. Flywheel Puller Type.jpg
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,924
I made my own using an L bracket.
Get a BIG L bracket , drill out the top hole so a heavier bolt can be used.
Then mount it using a 1/4-20 bolt.
The 1/4-20 is a bit light but will work, or drill and tap to 5/16 .
 
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