88 Force 85 hp drops to idle while @ WoT

[OhioCatman]

I recently purchased a 1988 Bayliner Trophy 17 ft with a 85 hp Force outboard. The problem I am having is rather strange. The motor always fires right up, idles with no problem, goes into gear and everything with no problem. The problem only occurs when running @ WoT on a plane for about 15 min, the motor sounds like it flutters and then all the sudden will drop to idle rpm and even sometimes immediatly increase rpm back to normal WoT. Motor does not die at all when this happens, it just drops to idle rpm. I replaced the fuel line and primer bulb going from the water seperater to motor after the first time I took it out and it did this as I was thinking it was maybe sucking air into the line or even water. I took it back out a couple days ago and it did the exact same thing, took almost exactly about 15 min again before it started doing it. Thanks in advance for the help.

 

[pnwboat]

Re: 88 Force 85 hp drops to idle while @ WoT

Sure sounds like a fuel supply problem. Is the fuel tank vent open to prevent a vacuum from building up in the tank? Might also check the tank itself to make sure there isn't any gunk in there clogging things up. Last thing might be the fuel pump diaphragm.

 

[OhioCatman]

Re: 88 Force 85 hp drops to idle while @ WoT

There is a small screen on the back which I am guessing is the vent, it is a little corroded but looks like its still able to let air in. As far as gunk in the tank I wouldnt know how to go about checking it as its not a removable tank. It is a center console boat made for fishing mainly on the ocean or bays and has a huge capacity, I dont know if this type is molded into the hull when they are built or how they work exactly. And if it was the fuel pump diaphram wouldnt you think it would be a constant issue instead of always starting about 15 min after its been running on a plane? I do agree that it seems like it is getting starved of fuel for some reason and there was a couple things i seen that i didnt like with the fuel line running from the water seperater to the motor, that is why I replaced that first hoping it was a quick cheap fix.

 

[tds1774]

Re: 88 Force 85 hp drops to idle while @ WoT

i have a 125 force that does almost the exact samething and i have rebuilt the entire fuel system! runs great for 15-20 min then starts fluttering back off to 1/2 or 3/4 throttle runs good and smooth do that for a few then wot will run good about 2 min then same thing. a buddy squeezed the bulb and it picked up a little but not like it should. I let you know what i figure out. gonna change plugs, and check the floats and see what happens. get back to ya soon

 

[pnwboat]

Re: 88 Force 85 hp drops to idle while @ WoT

You can verify the vent by opening the gas cap to allow air into the tank. See what that gets you. You should have some type of access to the tank. Usually close to the gas fill hose. There should be a circular plate with about 5 or 6 screws that hold it in place. This is the fuel gauge sending unit. If you remove it, you should be able to see into the tank.

 

[boating man]

Re: 88 Force 85 hp drops to idle while @ WoT

I have the same engine hp and all. Every time i put my boat in the water it does not get up to full speed unless some one pumps the ball on the fuel hose. i just replaced the fuel hose and that did not fix it but it is really hard to squeeze now while underway but still required to go max speed what could be the prob? thanks!

 

[bayliner Joe]

Re: 88 Force 85 hp drops to idle while @ WoT

did anyone solve this issue because my 85 hp us marine force is doing the same. I took the gas cap off and no help. just had all carbs cleaned and feul pump rebuilt. could it have something to do with the choke?

 

[boating man]

Re: 88 Force 85 hp drops to idle while @ WoT

I just replaced the fuel pump and still did not solve the problem. In fact it made it worse! now the boat goes underway at full throttle for about 2 minutes then dies out completely. .... i'm about ready to just junk the dam thing. but before i do anyone done a compression test yet?

 

[my1stboat1]

Re: 88 Force 85 hp drops to idle while @ WoT

has anyone come up with resolution to this .... someone mentioned there carbs were completely rebuilt... are the carbs syncd ? whats your air/fuel screw set too.. i figured out that my boat did something similar i took the boat out on a calm day with my dad took the engine cover off and took the air snorkle off the carbs... I got the ended hot and waited for it to act up.. I then adjust the air/fuel to 2 full turns out to the point it ran really rich and took it out again wot and it never did it again.. at that point i kepted turning the mix screws in 1/2 turn at a time till it acted up again once it acted up again i back it out 1/2 turn from that point and its been fine since... it did take some time maybe half a day and a serious *** beating on the boat i dont typically womp on it that hard but its done and worked out

 

[Wayland85]

Re: 88 Force 85 hp drops to idle while @ WoT

I recently had a similar problem and my mechanic put in a new water pump. That worked for my motor. He said the over heating was bringing the boat down to idle.

 

[chosos]

Re: 88 Force 85 hp drops to idle while @ WoT

I'm having this same issue. Did anyone ever fix this problem, or did you all junk your boats? I've replaced the entire fuel system, including the tank.

 

[mauiboy]

Re: 88 Force 85 hp drops to idle while @ WoT

I have to say like Wayland85 says the water pump might be the prob. I have a 88 85hp force and did not relize that some one disconected the buzer and did the same thing till I changed out the pump

 

[BonairII]

Re: 88 Force 85 hp drops to idle while @ WoT

Could the floats be set incorrectly( or have a restriction in the fuel supply) and you're running the bowls empty....they refilll and then you're running good again, and so on and so on?

 

[A.Hoj]

Re: 88 Force 85 hp drops to idle while @ WoT

I'm having the exact same issue with my 98' 90HP and still cant figure it out. I have a thread about it (90 hp ignition help) Seems like a very common issue. there has to be an similarity with everyone having this issue....I haven't been able to take the boat out and mess with the idle screws yet, but I'm hoping its just that simple. Ill let you know if I get anywhere with it. I'm close to just getting a different motor at this point fishing season is here.

 

[jkoppe73]

Re: 88 Force 85 hp drops to idle while @ WoT

Anybody notice that this original post is 2 yrs. old??

 

[chosos]

Re: 88 Force 85 hp drops to idle while @ WoT

Anybody notice that this original post is 2 yrs. old??

absolutely, which is why I raised it from the dead - I figure after 2 years someone had to take the boat to a repair shop or small engine mechanic to get the problem resolved, so they should be able to update the thread with a fix and help those of us still having this issue.

 

[jkoppe73]

Re: 88 Force 85 hp drops to idle while @ WoT

I must have misunderstood the announcement at the top of the forum

 

[bentle]

Re: 88 Force 85 hp drops to idle while @ WoT

We all mean well on here and its easy I guess to over look the forum rules.
If you need help with your motor then post a new thread.
If you know of a good fix for someone then reply.
Its really best to leave these older threads for info use only,
and the guys that did post on this thread 2 years ago are still
on here and ready to help.

 

[chosos]

Re: 88 Force 85 hp drops to idle while @ WoT

We all mean well on here and its easy I guess to over look the forum rules.
If you need help with your motor then post a new thread.
If you know of a good fix for someone then reply.
Its really best to leave these older threads for info use only,
and the guys that did post on this thread 2 years ago are still
on here and ready to help.

I'm sorry, I entirely skipped right over the announcement - I don't recall it being up there when I used to be active on here. Please feel free to lock this thread.

I actually created a thread a while back. check my history. I had no luck getting the problem resolved, unfortunately. Given the text in the announcement - I probably should have PM'd the guys in the thread, but I was hoping more or less to get the update in one thread, because this one keeps popping up when I use the search feature.

I haven't really been active on here since before that announcement was posted. Sorry again.

 

[jkoppe73]

Re: 88 Force 85 hp drops to idle while @ WoT

Now lets try to fix your problem, I have a 85 hp also, the only other things I can think of would be to check the exhaust boot that feeds the two cooling holes on the back of the leg, check for cracked rubber, exhaust will choke the engine out. also check the check valves in the fuel pump, old style will swell up from the ethanol fuel and will restrict fuel supply. And check the compession, don't think that is it because you are getting up to full throttle. also remove and clean the cylinder drain cover and screens. I never have experienced the overheating problems others talked about, so I can't comment on that....