Help!! What is wrong with my boat?

[Forbin]

Ok folks I just got it out of the shop with a tune up and clean carb. Put the boat it today and this is what happened:

1976 Crestliner with OMC 165hp inboard

Started no problem, got gas at marina and headed out on the lake. Was cruising at about 2500 rpms with no problem then I increased the throttle and just started to to move a bit fast and all of the sudden it felt like I was tied to a dock and a rope was pulling my boat to a stop. I to off the throttle and let it idle a bit then I hit the throttle again and it was moving for about 1 min and then bam! The same thing it just pulled right back. This happened a few time to the point where I had to head back to the marina going very very slow. I could no longer even get it going medium speed without the boat pulling and chugging along.

Is it the fuel pump or is there a leak. What do you guys think?

 

[superbenk]

Re: Help!! What is wrong with my boat?

Check the entire fuel path. Could be a stuck anti-siphon valve at the tank, the screen in the pickup tube might be clogged, filters might be clogged, fuel line might be collapsed internally and/or allowing air into the lines, water in the gas, phase separated fuel, etc.

This seems to be a problem that's been coming up a lot lately. I went through this on my boat & replaced all sorts of stuff. Seems like it was the anti-siphon valve for me.

 

[Forbin]

Re: Help!! What is wrong with my boat?

Under the steering wheel there is a tube going from the gas tank and around to the engine in the back. In the middle of the tube is a plastic or glass tube inwhich you can see the fuel in it. When the boat is off the tube has 1/2 fuel and 1/2 air. When I start the boat it is solid fuel. When I am driving the boat and experiencing a pulling feeling I look under an dit looks like air bubbles going through that glass tube. Is that normal?

 

[Fordiesel69]

Re: Help!! What is wrong with my boat?

No that is not normal to have air bubbles in the fuel supply.

Methodically work from the tank to the carb, not backwards.

 

[Forbin]

Re: Help!! What is wrong with my boat?

Ok so I will:

1) connect outboard fuel can

2) Check Fuel Filter

3) Check anti siphon valve

4) Check Tank vent


Any other suggestions? Should I check fuel pump pressure? Is there a chance the diaphram in my fuel filter has ruptured?

 

[SeanMcl]

Re: Help!! What is wrong with my boat?

If you have bubbles in a sight glass tube, you have an air leak somewhere in between your tank and that sight glass tube. Hows that for stating the obvious!

It's possible/probable given the age of your boat that you have a plugged up tank vent or pickup tube in the tank. This gives similar, intermittent symptoms to what you describe. When the fuel pump has to "suck" really hard to draw gas (because of the restriction in the fuel pickup or because the tank can't draw in any air), the increased vacuum in the fuel line starts drawing air into the line.

I know I did a bad job on that, but get a straw and poke a pinhole in it near the top. Drink from the straw normally, and you will be OK. Pinch the straw below the pinhole so you have to suck hard to get any water, and you will notice you are now drawing air into the straw where you weren't before.

A large leak in a fitting could also allow air in, but you would probably notice, by sight or smell, a leak that large. Either way, good luck!

 

[Forbin]

Re: Help!! What is wrong with my boat?

OK Thanks SeanMcl,

So how do I check if I have a plugged up tank vent or pickup tube in the tank?

K

 

[emoney]

Re: Help!! What is wrong with my boat?

Did you have the glass tube before the carb cleaning/tune up?
I'd ditch the glass tube for a fuel/water separator with a spin off filter.

 

[SeanMcl]

Re: Help!! What is wrong with my boat?

So how do I check if I have a plugged up tank vent or pickup tube in the tank?

If you can follow the fuel line to the tank and see where it connects, you can probably just remove the line, and unscrew the brass fitting from the tank. That fitting usually has the pickup tube connected to it so it all comes out as one piece. The pickup tube has a screen at the bottom that plugs up sometimes, or maybe there is gunk in the tube. I would also unhook the fuel line at the fuel pump and blow through it from the tank end, just to be sure there isn't a clog/pinch somewhere else, unless you test for vacuum as referenced in the next paragraph.

If that is a big hassle, use this link http://forums.iboats.com/showthread.php?t=283269 to build a vacuum tester and test the line between the fuel pump and tank for high vacuum. You should be under 5 inches of Hg.

As for the tank vent I just take of the gas fill cap, seal my lips to the hull around the vent and blow. If the neighbor walks by I start caressing the hull and rubbing my cheek on the outdrive, but I like to mess with him.

 

[Forbin]

Re: Help!! What is wrong with my boat?

Here is an update and another issue. I check the fuel line, all valves, changed all filters and put in a fuel/water separator. I then took it out and the initial problem where it was pulling has stopped. The boat ran great. Then this happened:

When I would stop and sit for a bit then restart it would immediately start but then stop. Then I would start the boat and it would run in neutral but as soon as I put it into gear to move it, it would quit again. Finally I could get it going. Why is this happening?

Also after I got it started it seemed like it was struggling to plain out. The boat began the day great and slowly started to get worse. When driving back to the marina I had the throttle down in a set position but the rpms kept fluctuating. At one point it felt like it was struggling at 2400rpm, then it would slow down to 2000rpm and then it would start running really nice up to 3000rpm. all this with out touching the throttle. Then when I got back to the dock and slowed right down the motor just stopped again.

I had the Carb checked and the marina said it was fine.

What would cause this to happen or is it the carb?

 

[SeanMcl]

Re: Help!! What is wrong with my boat?

I would say that you still have basically the same problem, it's just not bad enough to kill the motor anymore. Have you tested for high vacuum ( a restriction) in the fuel line, and for fuel flow to the carb (fuel pressure), and that the carb float bowl needle is operating and the float level is correct?

It sure sounds like the motor isn't getting enough fuel. Good luck, intermittent problems are tough to track down.

 

[Forbin]

Re: Help!! What is wrong with my boat?

OK so now I am starting to think my carb has an issue. With know prior carb experience would you recommend I open it up and see if I can find the problem. I have read a lot and watch many videos but never done it before. What am I looking for? If there is a problem with the float or needle what would I see or if it is dirty?

 

[joemamma]

Re: Help!! What is wrong with my boat?

Ok here's my 2 cents;
Check the routing of your fuel vent hose. Make sure there's nowhere for gas to get trapped in the hose and block the air in ,like a plumbing "P" trap. If that's good my money is on, Bad gas, I have pulled hundreds of gallons of ethanol out of fuel tanks. When an ethanol blend is exposed to moisture either in your tank or the marinas it WILL separate from the gasoline. and sink to the bottom of your tank where the fuel pickup is. and the engine dosent like to run on just alcohol. pull a sample from your fuel line before the filter, it should smell like gas. not kinda like gas but a real strong gas smell. if it doesent pump the alcohol out until you get to gas and change the filter again, alcohol will carry the moisture and clog up the filter.
FYI marine grade fuel can be up to 30% ethanol, automotive gas is only up to 10% That's why I fill up where I fill my truck.
good luck

 

[SeanMcl]

Re: Help!! What is wrong with my boat?

OK so now I am starting to think my carb has an issue.

Have you eliminated the fuel system as the source of the problem? Have you checked for correct fuel pressure and vacuum yet? If you haven't then you are doing the hard things before you do the easy things. Build a pressure\vacuum gauge and find out for sure if you need to take the next step and look at the carb.

Don't get fooled into thinking your problem has only one source. Old boats can have lots of problems that contribute to symptoms like yours, and you have to work through them all, one by one. Or you keep having trouble every time you hit the lake.

 

[Forbin]

Re: Help!! What is wrong with my boat?

OK so if I have bad fuel without draining it is there anything I can add to it to make it better and then fill up with good gas?

Also if I don't want to mess with the carb could I just use one of those carb spray cleaners? Do they work?

 

[Forbin]

Re: Help!! What is wrong with my boat?

Vacuum seems fine. I think I will try Seafoam treatment first and see how it runs.

Also is there anything I can add to the tank if I have some bad gas to clear it up. I can't remove my tank.

 

[superbenk]

Re: Help!! What is wrong with my boat?

If the gas is bad, there's nothing you can do but dispose of it and get new gas. Same with your carb, if it's clogged up inside, there's no canned magic that will clean it - you'll need to rebuild.

 

[airdvr1227]

Re: Help!! What is wrong with my boat?

FYI marine grade fuel can be up to 30% ethanol, automotive gas is only up to 10%

Huh?

 

[donberry]

Re: Help!! What is wrong with my boat?

While I would check my fuel 1st (carb), there is a possibility that your coil is going bad and breaking down under load. Points also, tho less a possibility. Has been more cars for me as I am a "new" boat owner, but I had a truck I restored once do something similar. Always kept breaking down under load, idled just fine. As I was "restoring" it, I went as far as buying a new edelbrock carb to put on it - still had the problem. Someone told me to check out my electrical system and the problem turned out to be the coil. Swapped in a new one and it ran great, tho I did switch over to a MSD ignition a couple of months later.

 

[Forbin]

Re: Help!! What is wrong with my boat?

Ok I'm getting frustrated!

I did everything with the fuel system and carb. Ok so now I am thinking it is might be electrical.

Why does my boat run perfect for 30 minutes? No problems. Go excelleration, planes great then after 20 or 30 minutes or after I turn it off. Then we I restart it, it is very sluggish, does not plane and can't seem to get going.

The battery's are charged but old and they still hold a good charge. Spark plugs have just been changed and points all done.

Now when the boat is running perfect in the beginning the battery guage shows the needle all the way in the middle but when it is running bad the battery guage needle is all the way to the left like there is no charge.

Is it electrical.

Again why does it run great for 30 min and then turns to crap??