1991 force 150 won’t plane out when hot

[Aquaholic90]

Hello everyone, I am new here. I’ve used iboats for years in the past for help but just via the googles and now I have a problem I just can’t figure out. My 20ft bayliner that ive had for 3 seasons now has a 91 force 150 on it. Since I’ve had it when it’s cold it will run 50-55mph no problem. If you keep on it and just cruise around without stopping eventually you will feel it just cut 1 or 2 cylinders or like today when out to the sandbar wide open no problem brought it back and trimmed up to idle in, sat for an hour idled back out and it will barely plane out and maybe goes 30 if you can get it up on plane. This has happened the same way for the last three years... I’ll tell you what I’ve done, something’s shot gunned others warranted...

Stator, trigger, rectifier, all 5 coils. Rebuilt the carbs (twice) synced the carbs, head gasket, exhaust manifold gaskets (those were pissing water out of the bottom) plugs, wires. Compression is lower but all cylinders within 2-3psi around 115. I pulled the plugs again today after the lake and they looked normal, nothing milky on them or anything. When it “cuts out” it sounds like it’s bouncing off a very low and spararic rev limiter.....please, someone help me I’m running out of ideas

 

[Aquaholic90]

Also went through the fuel pumps and replaced the diaphragms. Does the temperature switch on these cause it to go into a limp mode? Idk if these motors are that “smart” but I know other engines in that size and generation are

 

[Nordin]

There are no limp mode at Force engines.
Maybe I missunderstand you but is it cutting out 1-2 cylinders after longer time cruising at idle?
If it is doing that check the plugs if some (1, 2 or maybe 3) are fouled.
Two strokers do not like to run at idle for longer time. They do not burn all the fuel at low RPMs and the 50:1 oil ratio is for running at high RPMs.
The surface gap plugs which should be used in Force engines are more sensitive to foul then regular plugs with electrode.
If you have a timing light you can check for spark at each plug when it is acting like that.
If the light is flashing at each plug then the ignition system is okey.

 

[jerryjerry05]

Any idea of the model#??
You motor came with 2 styles of ignition.
The 89-91A used the Prestolite with 3 packs.
The 91B through 92C used Mercury.

The older model, it's possible one pack is failing and dropping spark.
The new style has 1 pack and it could do the same.

It sounds like it's getting hot after running and the pack or packs is breaking down?

You test the alarm system?

Fuel: how old are the hoses?
Ethanol can delaminate the interior of the hose and it can collapse and shut the fuel flow down?

Try running with the cover off?
Try a starting fluid spray test.
Once the motors running and hot, spray SF around the base of the intake side.
Include the part covers and carb bases. If it makes any change then it's sucking air,
probably a port cover gasket??

The comp at 115 is probably the gauge or the way the test was done.
The good: all are within 3#

 

[Aquaholic90]

Thanks for the replys. I will get the serial number after work, sorry should have given that right away. I have the ignition with the converter box and the single switch box going to 5 coils... I want to say it’s a 91d last Time I looked. It’s not at idle. It’s after she’s under power for a while. Sometimes I am get a few runs in sometimes I can only get one 3-5 minute run in.and yes it seemed like to me that a something was getting hot and breaking down. This was an issue for 3 years but it was always intermittent. So to my surprise this year when I went to go start it it ran like poo and I was like GREAT I CAN FINALLY DIAGNOSE IT! the lower 2 coils were open when I ohmed them out, put all 5 it and it ran great again.... on the hose. For the first runs of the day after that it ran great 50mph. Then once it got hot it shut down again. I did try the carb cleaner around everywhere with no change, when it’s acting up on the lake if I spritz the carbs it chokes it out no help so I was on the side of a spark issue. If I spray Around the bases also no change. And I have replaced the gaskets behind the carbs. The hoses are older but most have been off and look ok. I found the primer tube for the bottom carb was rubbed and replaced that no change. Primer bulb and hose were replaced as well.

 

[Aquaholic90]

I’m sorry to be so long winded I’m just trying to remember as I go what I’ve all done. I’ve also checked the check valves and hoses for the recirc system and replaced those gaskets behind those blocks as well.

 

[Aquaholic90]

I know this may not be anywhere near related to my issue but this video is EXACTLY how mine sounds and looks when it acts up. Sometimes it doesn’t even go that fast. But this is my symptom to a T. https://youtu.be/wWmFDt1tvFk

 

[jerryjerry05]

You test the overheat alarm?
Key on ground the orange lead at the buss bar.
The alarm should sound off.
That don't work? use a motorcycle or car horn.

Fresh or salt water?
You check the thermostat? One in there?
When you check look past the hole and see how much corrosion??
Impeller?

Try running on a spare tank.
Sometime the pickup in the tank clogs and can cause these symptoms.

 

[Aquaholic90]

Freshwater only. have not tested the overheat alarm. I will check that and the thermostat next. For safety’s sake I’m going to replace the impeller. Will an overheating engine cause running issues? And for the fuel issue if the primer bulb is hard while it’s acting up Should I still look into that? I’ve had someone back there pumping the primer bulb While it’s acting up and it doesn’t change and the primer stays pumped up. Thank you for your insight so far. Jerry, have read you are the force guru so thank you for helping. Do I look into the CDI switchbox? When I replaced the trigger the wires are very poor looking and didn’t feel the best. One thing I’ll add. IF it gets up on plane while it’s misfiring if I back the throttle of to a little less that 3/4 it seems smooth. Definitely not fill power but smooth and no shaking. The second I go full again it starts to shake and sputter just like the video. Don’t know if that is a clue

 

[jerryjerry05]

An engine running hot will do what you have going on.

The pump might be pushing enough water to work for a while and then fail.

The primer/choke it has a rubber diaphragm inside that makes it operate.
If the rubber's shot it can also make the motor run bad.
After it starts, pinch off the hose from the primer to the carb.
If that makes a difference then replace the primer.

CDI makes a good product..

Check the trigger leads?

 

[Aquaholic90]

Both the trigger and stator I replaced with CDI electronics components but The switchbox is original and the wires do not look good. It was hard to match them up to the trigger when I installed it. I did order a switchbox and an impeller kit... so I guess I’ll do those first and check the thermostat and see what happens.

 

[Aquaholic90]

Well.... update and I guess I don’t know where to go from here... I replaced the Impeller(old one was worn out but all whole) thermostat is working properly. Replaced the cdi switchbox with the part# specified by marine engine.com and I could barely keep the thing running. It was not happy at all. Also the fitment was poor. Dumbfounded I took it off and put my other one back on.stayed running fine...... Part was brand new from CDI. All the leads were correct and easy to pair because the trigger is less than a month old. I guess I’ll have to see if overheating iwas causing my issue cause I won’t be able to test the new switchbox.....

 

[Aquaholic90]

Well.... found my own mistake while installing the cdi switchbox took the boat out today and she is running good so far the couple hours we have been out. So. Either it was run it too hot or the switchbox was junk when it got hot. Thank everyone for their responses even for things that I might have checked over because it made me not second guess myself. Happy fourth everyone!!!

 

[Aquaholic90]

Just wanted to give everyone wondering an update, the issue is definitely resolved. Have 20-30 hours on it since and hasn’t skipped a beat