Hesitant, won't wot only sometimes.

[bfan781]

Hello,
I have a 98 mercury mariner 115 offshore outboard not used much at all over the years. Most important piece of info, I am new to boating. Not sure if related or unrelated, but I was running the engine with the vent closed (not on purpose) and after all the air was sucked out, it would barey run, very slow speed. any more any less would stall. I brought it carefully back to shore everytime. I realized the vent was closed, opened it, drained and replaced the fuel and it acted similiar again today, but not as drastic. Hopefully you can help me diagose the issue as I do not have enough cashola to drop at the shop at this moment. I have yet to do the fuel filter and I plan to do that tomorrow morning, but I do not think its the sole issue. What does this sound like? I know it can probably be many things. When I take it out when cold it seems to run a little rough and not idle properly, once warm it seems fine. I open it up and its fine, although it does seem a little hesitant. I throttle up, and there is a little delay before kicking in(little) not as spontaneous, but it works and does what it is supposed too. It seems, not nessesarily definite, that after going in no wake zones, very slowly for some time and then throttling, it does not speed up. I can be full throttled and the boat is moving but in slow slow speeds. The rpms are not racing either. If I back off the throttle a little and then throttle up, it may pick up slightly or engines revs higher momentarily, but just goes back to slow speed. Earlier I did that and the engine stalled. Get this, when I re-started, it was fine, able to open up (still slightly hesitant) but able to throttle up and down correctly? So I do not think it is something with over heating. It works properlt right out of the gate, then will not pick up and then today after stall and re starting, worked like a charm. Like I said, the fuel is brand new and the vent is opened. Should I use seafoam? Could it be something with the ignition? Any ideas? I don't want to get into cleaning/re-building carbs/compression tested unless that is definitely the problem? How should I diagnose and fixed the issue?

 

[j_martin]

Re: Hesitant, won't wot only sometimes.

Hello,
I have a 98 mercury mariner 115 offshore outboard not used much at all over the years. Most important piece of info, I am new to boating. Not sure if related or unrelated, but I was running the engine with the vent closed (not on purpose) and after all the air was sucked out, it would barey run, very slow speed. any more any less would stall. I brought it carefully back to shore everytime. I realized the vent was closed, opened it, drained and replaced the fuel and it acted similiar again today, but not as drastic. Hopefully you can help me diagose the issue as I do not have enough cashola to drop at the shop at this moment. I have yet to do the fuel filter and I plan to do that tomorrow morning, but I do not think its the sole issue. What does this sound like? I know it can probably be many things. When I take it out when cold it seems to run a little rough and not idle properly, once warm it seems fine. I open it up and its fine, although it does seem a little hesitant. I throttle up, and there is a little delay before kicking in(little) not as spontaneous, but it works and does what it is supposed too. It seems, not nessesarily definite, that after going in no wake zones, very slowly for some time and then throttling, it does not speed up. I can be full throttled and the boat is moving but in slow slow speeds. The rpms are not racing either. If I back off the throttle a little and then throttle up, it may pick up slightly or engines revs higher momentarily, but just goes back to slow speed. Earlier I did that and the engine stalled. Get this, when I re-started, it was fine, able to open up (still slightly hesitant) but able to throttle up and down correctly? So I do not think it is something with over heating. It works properlt right out of the gate, then will not pick up and then today after stall and re starting, worked like a charm. Like I said, the fuel is brand new and the vent is opened. Should I use seafoam? Could it be something with the ignition? Any ideas? I don't want to get into cleaning/re-building carbs/compression tested unless that is definitely the problem? How should I diagnose and fixed the issue?

Hate to say it. It's time to do a compression test looking for major damage.

You can do serious damage to pistons by starving them for fuel.

If you have poor compression, there's nothing short of an overhaul that will help much. If compression's good, we can troubleshoot any other faults.

John

 

[latin monkey]

Re: Hesitant, won't wot only sometimes.

you can try the seafoam to clean the carbs first to see if it helps, if not i would take them off for a good cleaning and rebuild. there is plenty of info on this site to help you if you haven't done it before

 

[bfan781]

Re: Hesitant, won't wot only sometimes.

How do you go about getting a compression test? Is that something a shop does? I only ran it for a short time with the vent closed. What do those symptoms seem like? Doesnt it seem strange that it, runs fine most of the time. How difficult is cleaning the carbs? any other advice or input?

 

[bfan781]

Re: Hesitant, won't wot only sometimes.

One more thing, if there was damage to the pistons would that cause it to only not wot sometimes? Seems like it would be more consistant. Can a compression test be done by myself with a kit? Does the boat need or should be in the water. Just seems like it only happened after a while and then once was turn off and on it fixed itself

 

[Coloradolakeboy]

Re: Hesitant, won't wot only sometimes.

I have been awakening my 175. I am going thru almost the exact same things.
I ordered the Mercury service manual (the original) and since I am low on funds also, tore into it. Mine will run poorly until warmed up after awhile it's fine. Here's what I have done.

1. Replace old fuel lines, connectors and fuel filters.
2. Replace spark plugs
3. Rebuild carbs and new needle/seats.
4. Rebuild fuel pump. Replace fuel lines from pump to carbs.

I hopefully will get her out this weekend and test but I am not confident it will fix all the problems. SO...

Next on my list is:
1. 7/16" spark gap test
2. compression test (should have done this first, but it's my dad's old boat and I'm a believer)
3.Test ignition with OHM meter and DVA

Keep us updated, and we can all learn together.

Here is JB's compression test, copied from the frequently asked questions area.

1. Fully charge battery.
2. Start engine and warm her up.
3. Remove all spark plugs and disconnect fuel line.
4. Rig a jumper to engage starter solenoid without turning ignition on. Pull the emergency kill switch on rope start engines.
5. Screw guage into #1.
6. Turn engine over until reading on guage stops increasing or 5 times, whichever is more.
7. Repeat #5 for all cylinders.

All psi readings should be within a 10-15% span.

* It has no effect to open the throttle.
* Don't get psi hysteria. Remember this is a 2 stroke engine and you are an amatuer at compression testing.
* Rope start engines will usually give lower psi readings than your know-it-all neighbor claims are required. Same for big JohnnyRude V6s
__________________
RED SKY at night. . .
JB

Great article, it is recommended for safety to do the "jump" instead of turning the key on. That way, you dont have any spark to ignite fuel fumes coming from the cylinders. I have read that you should also pull the kill switch lanyard. Eliminating the spark may also protect ignition parts, but I'm not sure about that....

 

[bfan781]

Re: Hesitant, won't wot only sometimes.

Coloradolakeboy, without a doubt we will learn together. I also will make sure I post the resolution when I figure it out. Seems like alot of people need help fixing the issus but when it is finally fixed they don't put the reason on the post, so when we search we only see the issue and the suggestions not what actually did the trick.

I am just lost as to wear to start.

If there was serious damage to the pistons, I feel as though it would be more consistantly not running right. If I through it in the water now, it would operate perfectly for a good half hour before the "not being able to open up" and other symptoms started to occur. I can not stress how in a blink of an eye, I was having the above issues and then it stalled, I re-started and it worked perfecty. Does that seem like a specific area I should check out? Seems to only happen after running for a while, yet, after stalling and restarting it seemed to correct it.
I really need some help, bad.
Any more advice or starting points would be extremely appreciated.

 

[Coloradolakeboy]

Re: Hesitant, won't wot only sometimes.

Is it a sharp cutout like turning the key off or a sputter out like you pulled the gas line off?

If it's a sputter, I would think fuel pump. If you have a stuck needle seat or stuck float in a carb, she can misbehave for a while, then be fine when the part gives in. Tough starting or no WOT can be caused by the same thing, not enough or too much fuel.

If it's a key turn off it's ignition

Get the manual and start from the beginning. Replace all fuel related items, rebuild fuel pump and carbs. Look at achris's DVA build and then tackle the ignition and diagnose it after you finish the fuel side. Could be some problems there as well. That's what I'm doing and it's a blast.

 

[Faztbullet]

Re: Hesitant, won't wot only sometimes.

As J suggested check the basics first...spark,comprssion,fuel. I would check the fuel pump as I have seen these suck the rubber disc's into the edge of inlets causing weak fuel pressure(since you ran with vent closed).

 

[bfan781]

Re: Hesitant, won't wot only sometimes.

Sorry for the newbie question, but where is the fuel pump located? Is it actually on the outboard or is it in the gas tank? The tank is built in. Is it possible to visually inspect the pump to check the rubber discs? If so how would I go about. Thanks!

 

[walleyemanII]

Re: Hesitant, won't wot only sometimes.

Check the fuel lines they may look like this inside

 

[pigeon laker]

Re: Hesitant, won't wot only sometimes.

Check out the check valves on fuel recirc system.If not operating right bottom cylinder floods.

 

[CharlieB]

Re: Hesitant, won't wot only sometimes.

What achris said, fuel pump and hoses.

Download the service manual here and start reading.

http://forums.iboats.com/showpost.php?p=2072211&postcount=3

Note the password at the bottom of the page, you will need it to unpack the compressed file.

 

[bfan781]

Re: Hesitant, won't wot only sometimes.

Ok. So it seem that I can do a compression test myself. Should that be done in or out of the water, or does it not matter. I read the tips and it seems easy enough. engine should be warmed up. Where can you get a compression tester? is it an expensive tool? Are they the same for cars and outboards?

Would you suggest that I do the compression test before anything else? Or because it often runs fine, does it appear the compression would be ok? And the compression test is just to see what the numbers are and prevent future damage?

 

[Coloradolakeboy]

Re: Hesitant, won't wot only sometimes.

You can buy a compression tester and spark gap tester for 7/16" at an auto parts store or Sears. Both tests can be done out of water. Warm up on muffs, turn off, then check compression and spark.

EDIT: Compression test is needed to see if you have serious problems that the other repairs can't fix saving you time if a motor rebuid is necessary.

 

[SeaKaye12]

Re: Hesitant, won't wot only sometimes.

Cheer Up bfan781...your engine probably does not have compression issues. I say that because I agree with your thinking in the sense that if it did have serious compression issues...it would **NEVER** run well...and you say that yours does run well sometimes.

But; testing the compression is so easy that you should certainly do it.

I would bet from what you are saying that it is a fuel delivery problem.

One thing that you could try is: When you are running crappily....squirt a bit of pre-mix fuel in your carbs...and see if the engine picks up speed. If it does; that carb is not getting/delivering fuel. If you find that to be the case; stop test-running and find the problem. Testing with a lean mixture like that is not doing your engine any good.

You could also have intermittent ignition issues. You could hook up a timing light when the engine is running and see if spark comes and goes. A timing light isn't too expensive; get one that works via inductance ...you just clip a pick-up on the spark-plug wires...easy! Some auto-parts stores loan tools.

One last thing....when you do a compression test you can certainly be out of the water; but I would hook up muffs to supply water to the pump. Otherwise you might damage your impeller. Probably not; but why take a chance.

Also.....when doing the compression test make doubly sure that you are cranking the engine **WITHOUT** ignition on. You do this the easiest way by jumping the terminals on the starter solenoid. Having ignition on without grounding the plug wires can cause expensive damage to ignition components. Be careful there.

Good luck, Chuck

 

[bfan781]

Re: Hesitant, won't wot only sometimes.

Thanks Chuck. I needed the reassurance. Though I agree I should and will do a compression test.

This is why I do not think there is any major damage. I took it out last night to try a few things. Would dirty carbs even cause this?

I ran it for a good 30m to 45 min. It ran perfect from idle to WOT. No hesitant, stalling or anything. Sounded and acted perfect.

After that time when I was in WOT in gradually seemed to loose power. Then eventually cut out. I attempted to squeeze bulb to see if it corrected it. It did not. I pushed in choke and that did nothing. I also threw it in neutral and it revved great and sounded as it should.

After a few minutes toggling the throttle it gradually picked back up and worked again. Once it began working the rpms were not as consistant as before and flucuated a little. It was working again though. Just strange. Like a volume that gradually went down to off then gradually back up to loud .Would dirty carbs cause this? Would like to feel as though if i do them it will fix the issues. What is your thoughts on carb rebuilds? somewhat easy to do? Do i need special tools?

 

[CharlieB]

Re: Hesitant, won't wot only sometimes.

I ran it for a good 30m to 45 min. It ran perfect from idle to WOT. No hesitant, stalling or anything. Sounded and acted perfect.

After that time when I was in WOT in gradually seemed to loose power. Then eventually cut out. I attempted to squeeze bulb to see if it corrected it. It did not. I pushed in choke and that did nothing. I also threw it in neutral and it revved great and sounded as it should.

After a few minutes toggling the throttle it gradually picked back up and worked again. Once it began working the rpms were not as consistant as before and flucuated a little.

When you tried squeezing the bulb was it partly collaped? Very soft, as if the motor was about out of fuel?

There may be something in the tank that gets sucked onto then blocking the fuel pick up tube. Once the motor dies the fuel line vacuum stops, the thing drifts away, you pump up the fuel and restart.

Try running on a portable tank of fuel to see if all is well, if so, then dive into your fuel system to find the problem.

 

[bfan781]

Re: Hesitant, won't wot only sometimes.

I actually just tried that. Hooked up a portable tank and it ran much better. Did not cut out and idled smoother.

It did drops RPMS at WOT from say 5500 down to 4000-4500, but other than that all the symptoms I mentioned above appear to be gone. So looks like I have two issues. A fuel issue before the motor and the RPM drops.

What would cause the RPMS to drop from 5500 to 4000 at WOT but have no other visible symptoms? Any ideas? Would dirty carbs do that? Or not because it runs great for ten minutes or so?

 

[bfan781]

Re: Hesitant, won't wot only sometimes.

When doing a carb rebuild, how important is it to torque the screws accurately? do you guys really do that? The torque screw drivers are really expensive and I can't see everyone doing it and buying one for the occasional DIY'er.

Thanks in advance