force 85hp missing under load and will only go to 3k rpm

[mtkrusmark]

so I have read this forum alot in the last 2 years as I have a 1988 baylinder trophy 17ft with a 1988 force 85hp motor. serial number for the motor is 856x8a.

when I bought the boat it had alot of issues but I got it to run up to 4k rpm at WOT after carb rebuilds, carbon fiber Reed valves, new fuel pump rebuild kit, and also a new trigger. the motor has never ran in the running range of rpm since I've owned it.

last year I had some issues with it so I decided to buy a clymer service manual and adjust the motor per the manual. (I also bought a 2 cycle timing light, a dva setup for my multimeter, and a spark tool to ground out the wires when testing or timing.) since I adjusted the motor to the manual the motor only runs to 3k rpm and misfires at any load more than idle. it fires up with just a flick of the key and doesnt overly smoke.

I run 91 octane non ethanol with valvoline 2 cycle marine mix oil.

I have tested the stator and also ohmed it, I was getting 259 volts on the high side and 197 volts on the low side, i had 630 ohms on the low side and 430 ohms on the high side. I also ohmed the spark plug wires and had 938 ohms average with every one over 900. when I hook up the grounding tool to the motor to time it it has bright blue spark on all 3 cylinders when cranking. when running at idle it doesnt miss at all.

i was asked my a marine mechanic if I'm getting any smoke out of the cowling when it misfires at WOT and I said no but I have checked the intake port covers and the gaskets were good. I also checked and cleaned the entire exhaust side of the motor by going through the exhaust port plate side.

compression on cylinders are 115, 113, 115 those were cold pressures.

out of the water it will rev out to 6k easy ( I know not to do that with just a hose hooked up but wanted to make sure it was load based misfire)

the primer gets rock hard when priming and I dont have any kinks or air in the fuel lines.

I'm running a 13x15 3 blade aluminum prop which I found to be the stock style prop, but I do have an aftermarket 19 pitch 4 blade prop that I have switched on it back and forth and in both cases the motor will go to the exact same rpm with either prop on it. I get more speed and it will kinda plane out with the 19 pitch on it. both props only let the motor go to 3k rpm and last year both props the motor would only go to 4k rpm.

the boat is not loaded any heavier this year than it was last year and I actually moved the batteries up front to help the weight transfer on the boat to help plane faster.

I'm at a loss of where I go next in the issue I'm having. if u have read this entire post and can think of anything let me know please. and thank you all for having alot of knowledge that I have read and has helped me up to this point

 

[Nordin]

You look like gone through the whole ignition system but as I assume you have the Prestolite system as it is a 1988 85Hp
I do not know what you mean with stator high and low winding.

The stator has three windings, two are feeding the ignition system and one for charging battery.
The two windings for the ignition system are feeding each power pack and the resistance should be about 680-800 Ohm (factory service manual does not have spec. for resistance, Outboardignition says 680-800 Ohm) at each one.

The DVA output should be 210 VDC or more at each one (spec. from factory service manual).
One of your shows a low resistance 430 Ohm and low DVA output 197 VDC.

The stator can show good resistance but still be bad, best way to check the stator is to measure the DVA output.
I would suspect the stator second winding for the power packs.

 

[jerryjerry05]

You test for TDC??
You do the static timing? What's your reading?
http://youtu.be/tDoR64jP5l8
It show how on an older Chrysler, but FrankA knew his stuff(miss him still)

Test the linkage?
Put into F (have someone turn prop as you engage, not running, you can bind/break if the props not spun
) see if the linkage moves the throttle cam all the way
Trigger: the wires are thin and break under the heat shrink and when throttled up the contacts can break.

You don't need 91 octane,no benefit, actually can make your motor run hotter.
https://www.google.com/url?sa=t&rct...regular-gas/&usg=AOvVaw0QSFdSxHJJMKUTaGeNAcEr

Clymer good to have if you run out of tp.
Factory manual a must.

Run with the cover off? try it.

Test at idle: starting fluid, spray around the intake side and see if it makes any difference?
Any stutter, bog, stall? yes? it's sucking air someplace.
Once up to speed does it run steady or bog down?

What's the speed?
What tach? factory?
Tiny tach, 20$ good tool to have in your box.

Comp is low but that could be the gauge?
The good is all 3 are the same.
Hot or cold, shouldn't make any difference.

 

[mtkrusmark]

I only listed the leads that dealt with the igntion for the motor but yes I did test the charging ones as well and they are within spec.

I tested tdc and also i know the key for the flywheel is not sheared off. I static timed it at 30 degrees, that is where the service manual tells me to put it with the prestolite ignition.

the trigger is good and tests fine, the whole tower moves as it is supposed to do, and I have replaced a couple of the plastic parts that the previous owner had cracked on the tie bar and the timing adjuster.

91 octane is the only fuel I can get where I live that has no ethanol in it.

I have ran with the cover off and still same issue.

once it does hit 3k rpm it seems to misfire about every 3 revolutions. but stays at that rpm.

the rpm is coming off the digital tach readout on my timing light that is hooked to the motor but also corresponding perfectly to the factory one in the dash. when I bought the boat I did use the switch on the back of the tach to match the timing light.

speed with stock prop 17 mph, with 19 pitch aftermarket prop is around 24

 

[jerryjerry05]

Try spraying the starting fluid?

The miss: you try running on a secondary fuel source?
Check for water?
Inline sparkies for testing while underway?

Unhook the tach and try running.
.
https://www.googleadservices.com/pa...hUKEwjAnqP7lK_iAhUiqlkKHbb9DHUQ9aACCDg&adurl=

 

[mtkrusmark]

I have ran on both the in boat tank, and a portable tank. both of which have brand new fuel and oil.

what would disconnecting the tach achieve?

i will run it with the spark tester hooked up and try that

 

[jerryjerry05]

Sometimes the old tachs ground out and stops the motor from reaching high RPM'S
The tach , since it's Bayliner the tach has a plug in connector.
Just reach around the back and pull on the harness, be careful as the tach's old and might come apart???
Aftermarket tach? find the pole that says "signal" and unhook it along with the power and ground.