couple of questions for a newbie need help

[bfan781]

I just picked up my first boat (used) and I am very excited. It was running good then started bogging down and not opening. After talking with friends who have boats we determined it bad gas. Sitting for 3yrs. Anyhow, these are my questions, now that the old gas is out should I do anything to the actual tank? I have read putting alcohol in it and flushing it out, but what if it all doesnt come out? My main question is (excuse the newbie here) where is the fuel filter located if i have one? is it on the engine or inside the boat? Should I add a fuel/water separator now? does that act as a fuel filter too? Where do they go on the line where the primer bulb is? Are they easy to install/expensive? lastly, I am thinking of doing the plugs since they are proabably old too and could be changed. Is there a good brand to get? do I have to worry about torque for them? I will gap them the same as the ones I take out. Any help would be great

 

[bfan781]

Re: couple of questions for a newbie need help

oh, I forgot its a 1998 115 mariner offshore on a 19' cc. Thanks!!!

 

[CharlieB]

Re: couple of questions for a newbie need help

Adding alcohol to marine fuel is NOT a good idea, up to 10% maximum is allowable, so says the factory manuals, over that engine damage can/will occur. You do not know what is in the pump so do not add any to stay on the safe side.

A fuel/water separator is highly recommended on all marine engines and wouldn't hurt to have on our 'land yachts' also. Install anywhere between the tank and engine that makes for a decent fit and ease of changing the filter annually.

Fuel additives, Sea Foam at a maintenance level as directed on the can, and fuel stabilizer if there is any possibility that the fuel will not be used within a month.

Nothing compares to a good carb cleaning, dirty fuel passages restrict flow causing not just the motor to run rough, but leans the fuel mixture burning too hot, melting pistons, and that is a serious problem. The Sea Foam greatly extends the time between cleanings, but you want to be SURE that your carbs are spotless to begin with.

Fuel lines, primer bulb, and fuel pump, all MUST BE clean, tight, no air sucking into the system and able to flow adequate fuel or the carbs go lean. Fuel line kits are not too expensive and should be changed at the first sign of any cracking to stay safe. Fuel pump rebuild kits are available and are also a suspect whenever WOT begins to drop.

Spark plugs, Merc generally spec NGK's, check their site for a catalog, you should find something like a BPZ8HS, the Z indicates a precious metal electrode which is more expensive than a BPR8HS which is much more cost effective. Gap .032 to .035 and change them annually for good measure.

Some owners run the same set of plugs for years until they finally start to fail, at the cost of standard BPR's I change mine and KNOW they are going to work.

You didn't mention the water pump impeller, the most important part of the cooling system. If you don't know its age, CHANGE it! And change it every other year, it is cheap insurance against an over-heat and and engine rebuild!

You can quickly learn to change an impeller in an hour, the effort will save you from buying a new engine. Period.

This may seem like a lot but once it is all checked you can be pretty sure you are not going to soon destroy your new toy.

If I left anything out I am sure the other guys here will jump in to let you know.

 

[bfan781]

Re: couple of questions for a newbie need help

Wow, thanks for all the advice and tips. Like I mentioned earlier I am new to all of this. I apprieciate all the info. So is there a good chance I have a fuel filter already?if so where is it located? In the engine? If I add a fuel separator does that act as a fuel filter as well? Are they usually installed in a compartment hidden? Lastly is there any online sites to get parts that is really good and recommended? I know for autos you can't beat rockauto . Thanks again!!!

 

[gregtobin]

Re: couple of questions for a newbie need help

I have a 77 Merc 115. This was also my first power boat. Some suggestions that I've learned over the past few years. First, always add fuel stabilizer when filling unless you are sure that you'll be burning it up within a month. If your boat sits for a while, the gas can also absorb moisture, so a small bit of methanol (5%) might help. Methanol will eat the rubber so, you don't want to use it very often or at higher concentrations.

Each year, replace the fuel line and bulb to ensure that the unit is in good condition. I put an inline filter just downstream from the bulb. A water separator is also a great idea as I've already konked out once when the fuel line sucked up a little water.

Pay close attention to how much water comes out the tell-tale. It should be a pretty good stream. Mine started to get wimpy and I found that the entire lower end was full of sand.

Good luck!

 

[dutchdog]

Re: couple of questions for a newbie need help

My 94 125 has a fuel filter on the port side of the engine by the carbs. Some mercs use gapless plugs, if yours have them then gapless plugs will needed to be put back in. I tried regular plugs years ago and only made it about 1 mile before they carboned up. Luckly I kept my old plugs and had my tools with me.

 

[bfan781]

Re: couple of questions for a newbie need help

thanks for the responses, let me give you a detailed account of what happened and maybe you can help me diagnose it. I bought the boat and it had been sitting for three years with 1/2-3/4 tank of gas. I heard it run and it ran strong. Before I put it in the water I add some new gas to it. Toppped it off. The first two times I took it out it ran flawless, idled good, opened it up, and ran smooth and strong. No issues. The third time I took it out, It ran good getting it out and after a hour or so, (first symptom) when I gave it gas there was a hesitation before it started going, but it did end up moving along. It didnt do that the first two times I had it out. By the time I was heading home it was moving at a very slow pace and the more I throttled it, it would either stall or bog, but it wont go any faster. Just slow.
I spoke with fellow boat owners that had a similar problem and they said it was most like bad gas being three years old. I drained all the gas, changed the plugs while I was in the process and took it out tonight. Before launching I filled up with new gas. On the ride out it ran great, idling and so forth and when I left the no wake zone, I opened it up, good reaction time and moved right along. After going for a little while I started to notice the hestiation I mentioned before where I throttle it and it hesitates before it got going. But it was moving. Then it came to the point where at full throttle it was slower than it had been ten minutes before but still was moving. Like resistance. Started to head back in and then it got the point where it would not go fast any more and if not at the right "spot" it would stall. Periodically it would rev at the point it was at. I did not change the fuel filter yet. I doesnt appear to be the gas. So tonight It ran good and strong and then after a half hour or so started the bogging and sluggish performance. Any ideas? I havent messed with any else, just drained fuel, and want to try and figure out what is going on. The first two times I saw none of these symtoms. Sorry for the long post, just trying to be detailed. I guess next i will change the fuel filter but not sure why it would run strong int he beginning then have the issues.
Thanks for any help or insight. Its apprieciated for a new boater!

 

[CharlieB]

Re: couple of questions for a newbie need help

"left sitting for 3 or 4 years"

You have NO IDEA how old the water pump impeller is, CHANGE IT!

With the key turned ON (but don't start the motor), ground the wire that is on the temp sensor, it should cause the overtemp alarm to sound, if it does not sound, you need to find out why, or you could be overheating, rebuilding that engine soon.

Pull those new spark plugs out and look at them, what color is each one, black, brown, white, speckled/spattered with melted aluminum (piston)?

Check the compression on each cyl, they should be over 100 and within 10% of each other. What are they?

You could be having a problem with the stator or ignition module heating up and failing to product a hot spark, DVA testing while hot will be needed to verify.

You could be having a restricted fuel supply caused by a plugged up fuel tank vent, run great til the fuel pump cannot suck hard enough overcome the vacuum and pull fuel from the tank. Continue to run WOT and a bogging engine WILL burn pistons, find the root cause of the problem before you seriously hurt your motor.

Check the things mentioned, ask more questions on anything you don't know about yet.

Let us know what you find and we can recommend what to do next.

Remember there is NO RETURN on electrical parts so don't even think of replacing anything until you test and PROVE something wrong.

 

[bfan781]

Re: couple of questions for a newbie need help

Charlie, I think I figured it out. The vent on the fuel tank below the gas fill is closed. After reading your response, I searched around and found out it needs to be open when in use. That should resolve the problem I would imagine right? No air gettign in. Chalk it up to still learning. First boat. luckly I did not keep it WOT for long so shouldn't have done any damage.

 

[bfan781]

Re: couple of questions for a newbie need help

hey, not sure if this got lost in all the posts. Being the beginner I am I had the fuel vent closed. I should have put two and two together. So from what I described as the symptoms would having that closed cause those issues? It would run fine until it was out of air and then could suck hard enough. I am going to try it hopefully tonight (opened) and see if it resolves the problem. The fuel vent has a screw cap with holes in it and a sleeve. when the sleeve is on and the cap is screwed in, it is not allowing air in. I assume that I have to take the sleeve off and screw that cap in allowing air to vent the tank. Sound right?

 

[CharlieB]

Re: couple of questions for a newbie need help

I don't know your particular tank with a 'sleeve', generally the portable tanks have a vent screw that just needs to be unscrewed a few turns to air the tank to 'breathe'.

Yes, pulling a vacuum on a tank will cause the motor to seem find for a little while then begin to loose power, bog and die, running lean and possibly even melting a piston in the process.

Test compression on each cyl to find out for sure if all cyl's are close to even.