Force 85 HP- 26 MPH :S

[Challenger84]

Re: Force 85 HP- 26 MPH :S

My OB is a 83' 70hp Johnson on a 16' Charger 1600 with a weight of 750lbs.
With a prop of 13-3/4 x 17

Well first I did a cylinder balance test to see which cylinder was faulty.

I ran the engine on muffs and started to pull the plug wires one by one to see it the engine hesitates.
I pulled the first one (Nothing happened) then pulled it back in
Pulled the 2nd the engine tried to stall so I plugged it back in
Pulled the 3rd the engine tried to stall so I plugged it back in
Conclusion:
Cylinder 1 was not firing.
Then I did a compression test to make sure they all have proper compression.
Found 130, 125,125 (all within 10% difference is good)
Then I did a Spark test.
All cylinders had good spark!
Then I opened up the carbs and looked to see if all the cylinders was getting fuel.
I saw all of then spraying fuel.

I grabbed some starter fluid and sprayed into cylinder 1 (because it was the faulty cylinder) and the engine revved up a little bit and idled REALLY nice..
It was purring as long as I kept spraying a little starter fluid into it.
So I came up with the conclusion that Cylinder 1 wasn't getting enough fuel into it.
I cleaned the fuel filter and adjusted the carb to cylinder 1 to let a little more fuel in. Put everything back together and now she runs like new!
VERY strong motor.
Gets me on plane almost right away and gets me going 42mph @ WOT.
with no gear no passengers and 2-3 gallons of fuel.

Hope that helps and keep us updated!!
Good luck!

 

[Frank Acampora]

Re: Force 85 HP- 26 MPH :S

Replace the exhaust snout! You may be venting into the prop. MINE: 15 foot Glastron V153 with a 90 HP Chrysler, 44-45 MPH. 5000 RPM on a 21 pitch prop, 5500 on a 19 pitch.

Your 85 would most likely take a 17 pitch and I would expect 35-37 MPH with just the driver in the boat.

Glastrons will allow you to raise the engine one inch on the transom. Lift the engine and use the bottom holes in the mounting clamps if the upper holes are the ones in use now. Otherwise drill two new ones. The cavitation plate should be one inch above the apex of the hull Vee. That alone will/should be good for another 2 MPH

If you do not have power trim, experiment with the tilt bar setting--usually the third hole out is correct. If you do have power trim, they usually like to be at fill trim out. Trim too far in or tilt bar too far in will let the boat "plow" and reduce speed considerably

 

[Big_C]

Re: Force 85 HP- 26 MPH :S

Replace the exhaust snout! You may be venting into the prop. MINE: 15 foot Glastron V153 with a 90 HP Chrysler, 44-45 MPH. 5000 RPM on a 21 pitch prop, 5500 on a 19 pitch.

Your 85 would most likely take a 17 pitch and I would expect 35-37 MPH with just the driver in the boat.

Glastrons will allow you to raise the engine one inch on the transom. Lift the engine and use the bottom holes in the mounting clamps if the upper holes are the ones in use now. Otherwise drill two new ones. The cavitation plate should be one inch above the apex of the hull Vee. That alone will/should be good for another 2 MPH

If you do not have power trim, experiment with the tilt bar setting--usually the third hole out is correct. If you do have power trim, they usually like to be at fill trim out. Trim too far in or tilt bar too far in will let the boat "plow" and reduce speed considerably

Thanks for the advice Frank.

Ive replaced the exhaust snout and it helped considerably. Havent checked on GPS- but feels much quicker. Third hole out resulted in getting on plane very quickly and the fastest feeling top speed...but had some porpoisng problems. I set it to two bars out, and it felt a bit slower but didnt porpose as much. Any suggestions?

It was tested with myself and a passenger, side by side in the boat. The cavitation plate is about an inch above the center of the bottom of the hull