difference between 1987 and 1989 85hp force

[monzingo1979]

First of all glad to be a member of the forum. Secondly I recently aquired an 87 bayliner with an 85hp force outboard. I was having trouble with the motor and didn't realize the high speed jets were clogged up and ended up burning a hole in one of the pistons (idiot newbie mistake on my part I know). The powerhead now needs to be bored and rebuilt. I came across a 1989 85 hp powerhead ready to go and was wondering if anyone could tell me if the parts (stator, flywheel, ignition system, and lower unit) from my 87 will bolt up and work on the 89 powerhead. Any help would be greatly appreciated.

 

[Nordin]

Yes it will fit.
The bolt pattern is the same and the drivshaft spline the same.
Ignition system is Prestolite and it will fit from both.

The 87 maybe have the black CDI box and ignition coils with connection plugs.
The 89 has the blue CDI box and coils and it has all connection to a terminal strip.

 

[monzingo1979]

Thank you very much! Yes my 87 has the black boxes. I have searched everywhere for that answer. You just saved me a good bit of money.

 

[tommarvin]

Welcome, I've never done it, buy you can change a piston without taking the power head off.
If your cylinder walls are ok, buy a wiseco piston and replace the piston with a hole in it.
If you need to bore and hone the one bad cylinder I would do that,then you have a known product that's good.
You still have to remove the power head to install the other power head, your not saving much time or $ getting the other power head.

 

[jerryjerry05]

Tom, did you read anything the OP wrote?

​The 87 and 89 have the same ignition system.
​The black packs and coils were replacements for the blue.
Blue was original equipment on all 87 and up.

The 86 was when they used the plug in connectors.
Late 86 they went to the buss bar and screwdown connectors.

They made a lot of $ when they introduced the black. They "suggested" that all the blue be replaced with black.
Suggesting that they weren't compatible???
They are.

Was the new powerhead rebuilt or completely torn down to rebuild??
Or a used block?
Pull the head and check the condition of the pistons and cylinder walls.
The gasket $ isn't that much and good insurance.

On the fuel pump side is the fuel recirc/ cylinder drain system. Looks like a long dog bone where a hose fits on the bottom.
You GOTTTTA make sure the screen is clear/gone and the reed is operating right.

This can contribute to piston failure , poor running and more.

If your mechanical? You can rebuild the old fairly cheap.

 

[monzingo1979]

The powerhead I have now with the burnt piston has bad scaring on two cylinders and would need to be bored. The 89 powerhead is in good used condition and has good compression on all cylinders. I plan on replacing all the gaskets, thermostat, and going through the powerhead before I install it. For the price I am getting it for ($200) I couldn't justify spending the extra money on a full rebuild of my powerhead if the 89 was interchangeable. Thanks for the tip on the recirculation system. When I took the one off my 87 the screens were packed full of metal shavings. I'm not sure where they came from?

 

[jerryjerry05]

Probably from the piston skirts.