Warm enging falls on it's face

[nikon4u]

I have an '88 Mercruiser 470 and it runs great for the first 20 to 25 minutes, but then it get's progressively worse. It starts to cut-out and fall on it's face at high rpm's and then it get's worse until it keeps dying everytime I put it in gear. It starts just fine, and I can rev it up real good in neutral, but soon as I put it in gear, it dies.

 

[Don S]

Re: Warm enging falls on it's face

http://forums.iboats.com/showthread.php?t=167561

 

[Four86Winns]

Re: Warm enging falls on it's face

Sounds very similar to a problem I was having. Went down to the other end of the lake and got stuck at the same spot every time. The motor would bog at full throttle. Then eventually stall anytime I put it in gear. Just did a tune-up and it's all better. New cap, rotor, points, plugs, plug wires. It all came in the tune-up kit. To check if you need a new cap or plug wires, start your boat up at night, when its really dark. Look under the hood, if you can see sparking (little blue flashes) there are hair line cracks. I, too, thought for sure if was a fuel system problem, because after adjusting the carb it improved, but that just masked the problem. And I thought I'd start with the cheap stuff before moving on the the expensive stuff in the fuel system. Good Luck

 

[nikon4u]

Re: Warm enging falls on it's face

I like it! I think I'll get the new cap, rotor, points, and maybe new plugs. I want to check for the sparking on the wires since they are pretty pricy. I did rebuild the carb this morning and it seemed to help out a lot, but when I was about to take it out, it started doing it again.

PS
unleaded gas on the road in KC is about 3.19! At the marina...2.85! I totally filled up and filled my 5 gallon tank too!

 

[Four86Winns]

Re: Warm enging falls on it's face

oh, and I forgot to mention a new condenser too, but thats all part of a tune up anyway. Also, even if they don't spark there's still a chance they're bad, just if they do spark they are definetly bad. And before you buy anything, check to make sure there isn't any condensation under the cap, a hair dryer will fix that for you. But chances are you'll probably need a tune-up, if you're like me and your boat sits on the water throughout the season with all the condensation over the water, you'll need a tune up at LEAST once a season.


P.S. Amazing that gas at the marina is actually cheaper, I thought it was a law that everything had to be more expensive at a marina.

 

[Coors]

Re: Warm enging falls on it's face

Maybe?, and most amateur carb rebuilds don't work, as the correct chemicals are not availiable.

 

[nikon4u]

Re: Warm enging falls on it's face

Not sure what you mean by that statement. I have rebuilt about 30 carbs before and even rebuilt 5 whole engines, so I'm no average Jo around engines, if that was a dig. I'm sure that you have more experience than me, and am assuming that you would change the plugs for sure. Do you also agree that it sounds like it isn't in the fuel delivery system?

 

[180Diablo]

Re: Warm enging falls on it's face

P.S. Amazing that gas at the marina is actually cheaper, I thought it was a law that everything had to be more expensive at a marina.

Yeah really, up here in canuckland its almost a dollar more per litre on the water than on land. Last summer/fall it was approx .70 to 80c/litre on land and around $1.70-$1.80/litre on water. This summer its $1/litre on land and .. well I dont think I really want to see what the price is going to be on water this year. Some reports saying $1.20/L or higher on land by this summer. So I would assume we would be looking at $2/L on water.

Which I would hope it would start to cripple the whole boating and tourism industry, then maybe they would lower the prices to match what is on land. I guarantee that there will be a noticeable lack of boaters this year on the waters if the price of fuel keeps on going up. Larger boats will now become floating cottages only.

 

[hullofalottatrouble]

Re: Warm enging falls on it's face

i would do the fuel system tests anyway.. they are easy to do and a new anti-siphon valve isn't really an expensive part but a bad one can cause you some problems.. i had all kinds of problems with my old engine but it behaved just as you describe.. one of the things i found was a bad anti-siphon valve it was restricting fuel flow.. easy to test and easy to replace..

 

[nikon4u]

Re: Warm enging falls on it's face

Can you tell me more about the anti-siphon? What does it do? Where is it in the line? What does it look like?

 

[Coors]

Re: Warm enging falls on it's face

It stops fuel from coming out of the tank if you overturn. It is usually the first fitting coming out of the tank, to the engine. They can get gummed up- been there (has a ball in it/check valve.

 

[cydonia333]

Re: Warm enging falls on it's face

Just came across this site tonight... I am having the same problem... but this past weekend when it did this.. I pulled a seat cushion that was over the engine giving me the problem... while trying to figure out what was going on, I restarted the motor and it ran fine..
I can only guess that the airtemp inside the engine compartment must affect it some how... I was thinking of hooking up a air blower that will blow on the carb. itself..

The rest of that day I left the cushion and never did have another problem