1987 Force 85HP Bogging down at WOT

[pmcd1222]

I've recently purchased a 1987 bayliner capri bowrider with a 85hp force outboard on it.

The engine turns overs, idles, and accelerates perfect. My issues begin when I'm at WOT for about 20 seconds.

The boat acts like it's needing more fuel in order to get back up to higher rpms.

I've replaced the fuel line from tank to filter. The squeeze bulge holds pressure telling me there's no issues with holes in the line or tank.
I've replaced the fuel pump diaphram, fuel filter, and fuel lines between the fuel pump and carburetor as well as the lines between the three carbs.

My guess is the carburetors. But that's a just a guess. Any help in terms of other things to first double check would be greatly appreciated.

I'm not the most knowledgable mechanic, but I'm learning a great deal each day with this boat.

Anyone with advice or similar issues, I'd love to know what other things I should be trying to identify.

Pat

 

[Jiggz]

Many people are very hesitant to install a clear fuel filter between the fuel pump outlet and the carb's inlet. But the fact of the matter it costs less than $5 to put one and it even comes with the hose clamp. And it is indispensable for all fuel related problems. If you have one installed, the clear fuel filter should stay at least half full all the time. If it doesn't that means you have fuel delivery problem, i.e. faulty fuel pump, leaky fuel hoses or clogged suction tube. If it stays at least 1/2 full, then it is a carburetion problem, i.e. float improperly set, clogged jets or it could just be simply improperly set timing or misfiring.

 

[jerryjerry05]

Clean the carbs and check the floats.
Possible?? the floats are set wrong?
Check the drop.
​In the squeezie there is a one way valve.
After time Ethanol can delaminate or melt the valve.
Try replacing it.

The squeezie gets firm and after startup it shouldn't stay hard.
It shouldn't collapse either.

The inline connectors have a seal that can leak and suck air.
Tank, built in or 6 gal remote?
The vent hose can get clogged and cause a problem.
The tank pick up tube also can get clogged.
Some pickup tubes had a filter on the end and it would fill with crud and slowly kill the motor.
Install the filter Jiggz suggested.
I install them between the carb and the pump.

 

[pmcd1222]

Thanks for the responses.

I'm still chasing this in circles.

I decided to pull the carbs for visual inspection and to clean with carb cleaner. Once I cleaned them up and put them back on the engine, the engine is running way worse than it ever has. It bogs down and wants to die if give it any gas. But if I have someone drive and I pull the choke for all three carbs as we're moving, the engine wants to accelerate like it should.

I called a mobile marine mechanic who came over and said "he rebuilt the carbs to perfection". Although when we went out on the lake together, the boat continued to do the same thing. I'm not very trusting of this guys work, too say the least.

He explained that he thought it might be the reeds behind the carb. I pulled the carbs again and got to the reeds. They all look great.

I have three theories and I'm hoping you might be able to help me confirm or dismiss them.

1. The carbs are still not right. The lowest carb seems to be leaking a bit of fuel on the bottom of the fuel bowl. I'm wondering if the mechanic simply did not rebuild them correctly.

2. The timing is off. The engine starts right up and doesn't backfire except every now and then if I open up the carbs in neutral at the dock. I'd say maybe one ot of every 10 times I try. Would timing throw off fuel distribution or spark to the cylinders when in gear? Or if timing is off, does the engine typically have trouble starting in general. My engine turns right over at start.

3. The fuel tank exhaust is clogged. It's an built in tank. Seems to me like the hoses look pretty good that exit the tank. I would think if this were an issue, revving the engine in neutral would still present issues.

I bought this boat about a month ago. When I first took it out, it ran fairly strong, other than my initial problem of struggling for fuel at WOT. Now it seems like I'm spending every free hour of my day working on this thing, and it continues to get worse. Any insight to my issue would be greatly appreciated.

Pat

 

[pmcd1222]

I also checked compression. 145 on all three cylinders. So I believe this engine is worth putting the time in to.

I have already purchased the inline fuel filter to insert between the fuel pump and carbs, it's going on as soon as I have the chance.

The local boat shop I trust, really thinks it's still in the carbs. He employed the mobile mechanic I hired and needless to say, that guys not working for them anymore for obvious reasons. I plan on pulling the carbs again and closely inspecting the work done. I have a feeling it might be a gasket not seated correctly on the lowest carb. That's my best guess considering the fuel bowl has fuel on the bottom of it if I swipe my fingers beneath.

Again, all the help is greatly appreciated!

 

[Jiggz]

Post your results on the clear filter as soon as you get it installed and do some test run.

 

[jerryjerry05]

First few posts in the Force Forum have real useful info on timing and carb setup.
FrankA did a real good job on some maint. posts.

Age,Ethanol and hoses: E delaminates the inside of the hoses and you can't see the damage.
If you can grab the hose and it's real soft and the outside comes off when you touch it then replace it.

​Tank vent and operation at idle: a motor with a bad cylinder can rev at high rpm's without a load.
The clogged hose lets in enough fuel at no load and the motor can run wide open.
The motor uses a lot more fuel under load and the clogged hose limits it.

There has to be a vent for the tank, can bugs get in??? try blowing through the hose.
DON"T use compressed air. BOOM!!

A factory manual even a Clymer or Seloc (not my choice) will help in the rebuild.
You local library should have or can get you a book.

The timing has no effect on fuel delivery.
The pump is operated on vacuum from the intake side.
The faster the motor revs the more fuel is pumped.
Try rebuilding the pump valves too.
In 35 years I've only seen 1 bad valve in a pump.
I took the pump apart to replace the diaphragm and the valve fell apart and dropped out.
The funny part was there was no problems and the D change was just PM???

The timing: if no one touched it then it's probably ok.
It doesn't jump like a car.

The backfire or stutter or cough at idle: probably the air screws on the carbs probably set wrong.
Initial setting should be at 1 and 1/4 out from lightly seated.
The factory suggested turning them out to 1 turn and leaving it there.
My twin 88/85's run great at 1 and 1/8th out.

Get your $$$ back fro the boat butcher.

 

[pmcd1222]

The problem turned out to be that the guy I paid to rebuild the carbs had the fuel jets and air jets backwards on 2 out of 3 of the carbs. I found a diagram online and once I switched the jets, the boat runs perfect. I called the mobile mechanic and he gave me a good portion of my money back. I'll give him credit for that, just not the work he did.

Anyway, thanks for your posts. Problem solved and you all certainly gave me insight to focus on the right things.

Thanks;
Pat