I have the newer Force on..but need tuning suggestions

[mike 1985]

I comp. tested the new motor (early 90 Force 85 from Bayliner bass boat) and I got 135 each cylinder. So I installed this one and decided to keep my orig. 1989 as the spare.

This motor sat for 7 months before i bought it. I got it to start with the help of a little starting fluid. It idles at 500-600 RPM. It reves up good in neutral, but when I put it in drive it stalls. I think because the idle is too low. After messing with it I took it back out of the water and home. I couldn't get it to restart with the ears, only sputter.

I'm going to clean the carbs and put new plugs in it and try it again, so I have 2 questions.
1- how do I raise the idle ? I see a small rod with 2 adjustable ends that hit the throttle blades, but also a screw that goes to the block with a nut that can adjust too. what should the idle be in Neutral ?

2nd. I thought the low speed screws were supposed to be about 1 turn out each ? This one seems the same as my previous one being..
top 1/2 turn out
middle 1 turn out
bottom 1-1/4 turn out.

Is this correct or should they all be equal ?
Thank you very much

Any help is appreciated.

 

[steelespike]

Re: I have the newer Force on..but need tuning suggestions

Idle mixture screws initial setting is 1 turn out from gently bottomed.And then adjusted as nearly alike as possible in gear warm.My manual has no info on idle speed but I would say 700 to 750.
Carb tie bar needs to be adjusted so throttle plates open the same amount at the same time.There is also a carb/ignition sync adjustment.
If this motor has sat a lot you may have fuel system problems.
You should get yourself a service manual.Sometimes you can find manuals at the library.

 

[mike 1985]

Re: I have the newer Force on..but need tuning suggestions

I remembered Frank also said 1 turn out, I just thought it was ironic that both motors were pretty close to the same. The carb tie bar is good.

I've been looking for a manual on e-bay...so far no luck. I'll be headed to the library tomorrow.

thanks
Mike

 

[Frank Acampora]

Re: I have the newer Force on..but need tuning suggestions

Factory says that all needles should be set equally to the average setting of all three. so 1/2, 1, and 1 1/4 should average to about 7/8 to 1 turn out.

1/2 out is definitely too lean. Do not run the engine with it at that setting.
Idle should be about 700 RPM in forward gear in the water. Depending on the pitch of your prop this may be somewhere around 1,000 or slightly more in neutral.
Near the bottom of the tower shaft is the idle set screw with locknut. It is the one that bears against the block at idle. Small adjustments go a long way with this screw. Adjust then run engine in gear, then go back to neutral. Setting will have changed a little because of compliance in system.

 

[mike 1985]

Re: I have the newer Force on..but need tuning suggestions

Ok, I have them all set at 1 turn out, and raised the idle as you stated Frank. It's very good now. The motor idles great, goes into gear easily and runs nicely. Top RPm was 5300 @ 37 MPH with 3 adults and 1 70lb 10 year old. I'm very happy with that. BUT...

I could see smoke (steam) coming from the back of the motor. Shut it off and felt head...definatly felt hot. I let it cool 45 min and drove back slowly.


I need to know about parts interchangeability with the 2 motors I have. Their both 85HP. The orig one I got on the boat 1989 maxum ( serial # missing ?) has a blk cover with grey 85 fancy #'s. The head is blk with cooling fins vertically in it.

The new one is Model 856X7A..serial # 2988. What year is this one ?

The orig motor I could touch the head even after running for a bit. I also just put a brand new impeller in this one. Can I swap it into the other motor ?

I also thought I would swap the thermostats, but there installed differently. The orig 9 blk head with fins) has the pointed opening facing away from the motor with a big coil spring between it and the housing. The new one has the pointed part facing the motor with no coil spring ? Which way is correct, and are the thermostats interchangeable ?

I'm sure learning how to work on these things, but it's time to start enjoying the boat with the family.

thanks

Mike

 

[Frank Acampora]

Re: I have the newer Force on..but need tuning suggestions

All parts are interchangeable, including the thermostat. The only thing that may be different might be the electronics and the only difference there is that one (Prestolite) has quick connector terminals and the other has all connections on a terminal board below the CD boxes. Engine and ignition switch are wired the same though.

The old style head has a hole too small for the spring end of the thermostat to go in so it is installed with the pointed end into the head. (actually incorrect because the spring end has the expanding pellet and should be exposed to the hot water in the block--a little more accurate control--it still works though.) The cover holds the rubber gasket tight. The newer style finned head has a large enough hole in it to install the thermostat in it the correct way. Spring end goes into the head toward engine. However, the thermostat cover will not hold the rubber gasket tight, so a large spring is used inside the thermostat cover to push against the thermostat and rubber gasket, thereby sealing it to the head.
When running the engine the head should be hot--uncomfortable to the touch, but not hot enough to burn you. Remember, depending on thermostat temperature you are trying to maintain water temperature at either 160 or 180. However, you should not see steam issuing from the idle relief holes. Take out the thermostat and check it on the stove in a pot of water to see that it does indeed open, and replace the impeller--even if just on general principles.

I think your 85 has a 2 to 1 lower gear ratio. If that is correct, the prop is spinning at 2650 RPM and with a 17 or 19 pitch prop, 37 sounds about right. Don't have my calculator in front of me though. Figured it out once though. If I remember correctly: With a 19 pitch prop Theoretical at 2650 would be about 42 minus 10% or 38, with a 17 pitch it would be about 39 minus 10% or 35 mph. So, you are close.

 

[mike 1985]

Re: I have the newer Force on..but need tuning suggestions

I swapped the impellers, It was wore out. The other motor was wore out. Huh you say the newer head is the finned one ? That's the one from my orig motor. That's also the one I cut .022 to clean up and have a brand new head gasket just sitting there. Maybe a after season project ?

The thermostat was open when I took it out of the motor and closed as it sat on the bench for a while.

I could tell from the sound something wasn't just right. When I stopped and checked it, it was hot..burning your hand hot. I knew from the previous motor that after I put in the new impeller I could touch the head and block even after running it. I should be good to go now.

All the help and advice is MUCH appreciated.

Mike