Please help me figure out what is wrong with my force 120.

[r81gsr95]

Hi guys, i will try and do my best to explain my situation, please try and bear with me. I just bought my first boat, its a 1994 17 foot maxum with a 120 hp force on it. Yesterday my dad and i took the boat to a mechanic friend and we couldn't get it started all day. We believe the engine keeps flooding itself. it is getting spark and fuel. Today we redid the battery connections because they were pretty bad and put a new battery in it. It took us about an hour to get it started but we finally did by spraying some ether(sp) starter spray into the top carb. It fired up and we let it run for awhile. Upon cool down it would fire right back up without having to give it gas. So what we did then was take it down to the lake and we ran it for awhile. It ran alright, with me and my brother in it i got up to about 41mph trimmed. Does that sound right? I would think a 17 footer with a 120 would go faster but idk.

After about 20 minutes of test running it, i tied it up and let it sit for about 2 hours. After that i cuoldn't get it started again. It would just flood it self. I tried removing the sparkplugs, airing it out and then trying again but same outcome. I had to have it towed in. If you guys could please give me some things to walk through and check i would greatly appreciate it. Someone told me that the starter might be drawing too many amps and not giving enough spark to the plugs to ignite all the fuel. is that possible? It's very confusing to me beacuse when i bought the boat the engine would always fire up great and easy. Also one last thing, when i pull the plugs out to air it out, i would crank it over for a few seconds to blow everything out of the cylinders but i noticed that gas would mist out of only 1 cylinder. the 3rd one from the top. Why would it only come out of that cylinder? Could i have a problem with my lower carb? Thanks guys

 

[bowhuntrrl]

Re: Please help me figure out what is wrong with my force 120.

Sounds like you need to take the carbs off and clean them and also check the needle and seats for sticking. You should spend some money on a good manual, probably a Clymer.

 

[roscoe]

Re: Please help me figure out what is wrong with my force 120.

Welcome to iboats.

Simple and easy repair if it is indeed flooding while it is sitting.

THe fuel pump is leaking on the inside, into the crankcase.

Get a fuel pump rebuild kit from Mercury, about $18.

A very common problem with 10-15 year old Force motors.

 

[Racer]

Re: Please help me figure out what is wrong with my force 120.

I have a 19' with a Force 125 and it has a top speed of about 38-39 mph, so 41 on a 17' is probably about right.

 

[QuadManiac]

Re: Please help me figure out what is wrong with my force 120.

I have an 18' with a Force 90, top is 34. 7 MPH with the extra 30HP sounds in the ballpark.

 

[r81gsr95]

Re: Please help me figure out what is wrong with my force 120.

thank you guys for the replys. I took the fuel pump off and opened it up and sure enough the gasket was torn in the middle. You could see where fuel was passing through. So i put a new gasket on it thinking it was going to solve the problem but i still couldn't get the engine to start. Anyone else have any ideas? This killed my 4th

 

[Bigprairie1]

Re: Please help me figure out what is wrong with my force 120.

...ok back up. Will it start with an ether injection? If so...this is a carb(s) problem or more specifically a fuel delivery problem.
Remove the carbs, clean the carbs, fix the carbs, set them up, check your fuel pump issues, fix your fuel delivery problem...and you will beat this problem. Whatever you do...don't putz the problem. Don't be afraid to remove them and professionally clean them either yourself or at a shop. While you are at it...do a compression test...this will give you info on the engine condition and info on your max speed question.
This work will pay in spades.
As for maximum speed....I'm running an 18' with a Force 90...I'm pushing 38-40mph. You should be good for something over 40...maybe 45mph. A lot of this depends on your trim, your prop, your tune, empty bilge, etc.
Good luck.

 

[roscoe]

Re: Please help me figure out what is wrong with my force 120.

Can't just replace the gasket.
You need to replace the diaphrams.

 

[r81gsr95]

Re: Please help me figure out what is wrong with my force 120.

okay i rebuilt the fuel pump and at first it wouldn't start up. I finally got it running and so i took it down to the lake to swap trailers. I let it run for about 5 minutes then shut it off. After that it wouldn't start again. I still haven't been able to get it started. All 4 cylinders are getting spark and the fuel pump is working fine. What else could it be? How much would it cost for the olympic boat center to tell me whats wrong with it? THanks

 

[MikDee]

Re: Please help me figure out what is wrong with my force 120.

One thing you want to watch out for, is once it is started for the day, you usually don't need the choke again, because these engines flood easily, don't use the choke when warm, unless all else fails, but it sounds like your carb floats, and needles are hanging up causing the carbs to flood out, I would go through them and check it out, if I were you.

 

[RRitt]

Re: Please help me figure out what is wrong with my force 120.

well ... a couple of things.

I don't think you should shoot ether into the engine to start it unless you can find some ether with 2-stroke oil mixed into it. Someone with more knowledge can chip in tell you for sure but i think you might tear up your engine very quickly with aerosol starting fluids.

If you put up your boat for winter with gas in the carbs then the gas evaporates and leaves behind a residue from 2 stroke oil. after a few seasons the accumulation can be significant enough to cause starting problems. When you have checked everything out and you know that you have good compression, good spark, and good fuel delivery ... then gummed up jets is a reasonable suspect.

 

[r81gsr95]

Re: Please help me figure out what is wrong with my force 120.

well ... a couple of things.

I don't think you should shoot ether into the engine to start it unless you can find some ether with 2-stroke oil mixed into it. Someone with more knowledge can chip in tell you for sure but i think you might tear up your engine very quickly with aerosol starting fluids.

If you put up your boat for winter with gas in the carbs then the gas evaporates and leaves behind a residue from 2 stroke oil. after a few seasons the accumulation can be significant enough to cause starting problems. When you have checked everything out and you know that you have good compression, good spark, and good fuel delivery ... then gummed up jets is a reasonable suspect.

how can i go about cleaning the jets? Will i be able to do it without having the engine running? Thanks

 

[QuadManiac]

Re: Please help me figure out what is wrong with my force 120.

Shooting ether into the carb throat will not clean the jets. They need to be removed, cleaned with a solvent and then dried thoroughly with compressed air. Running Seafoam or an equivalent cleaner in your gas will help keep them clean in the future, but if they are all gummed up, the only way is removal, IMO. Comments, anyone?

Good luck!

 

[r81gsr95]

Re: Please help me figure out what is wrong with my force 120.

There has to be something mechanically wrong. It will run one minute and then not the other. I need to have this turnkey.

 

[bowhuntrrl]

Re: Please help me figure out what is wrong with my force 120.

You are being given a lot of good advice that you are ignoring !! The carbs need to come off and be overhauled, it's that simple. No amount of additives or spraying is going to fix your problem. A proper repair is needed, and that entails taking the carbs off, disassembling them , soaking in cleaner, and reassembling and adjusting to specifications. If you can't handle this, you need to take it to someone who can.

 

[RRitt]

Re: Please help me figure out what is wrong with my force 120.

I put my boat up every hurricane season and the lift doesn't come back down until the tourists are gone. every year the engines got harder and harder to start. It got so bad that I wouldn't even try starting left engine until after the right one was running for fear of killing both batteries. at first it would start if i repumped the sqeeze bulb. then sqeeze bulb didn't work and I could smell flooding in engine.

took carbs off engine and cleaned them with pipe cleaners. It was much easier to do than I thought it would be. The choke linkage was tricky because of small parts and it had to be reassembled in specific order. but carb synchronization was laughably easy and it was the main reason I was avoiding the job. Only parts needed were new carb to manifold gaskets. put mixture screw back at factory default as per manual. started right up on first spark, idled perfect, ran perfect. left engine went from being a finicky little sob to running like a brand new motor. I think you have same problem.

 

[elesar]

Re: Please help me figure out what is wrong with my force 120.

Sorry if I've missed something, but this thread is too long and confusing. Has anybody suggested checking the "pull out and push forward" operation for cold starts on the Maxum/Force controls?