merc 3.0 stalls

[jt3kids]

Hey all. First time at the Lake, wonderful weather. Have an older boat, 3.0 merc 4 cyl, mechanical fuel pump, coil, etc. Everything new ( except fuel pump). This thing starts, and runs fine for 10 mins, then stall, like someone shut off the key. the longer I let it cool, the longer it will run. After it stalled I checked spark from the coil, and it was perfect. I bypassed fuel/water filter, and still no difference. new gas + additive for moisture. I took off fuel line intake to Carb and cranked engine. Fuel came pouring out. I disconnected RPM wire from coil ( TACH didn't work anyway), just incase it was that... When its cold, it starts right up and runs perfect. New T-stat, water pump, lower unit rebuild, starter, batt, wiring, IGN switch, etc. I am at my wits end. ruining vacation at this point. Any ideas would be extremely helpful. Also, does anyone know of a mechanic that would do house calls tomorrow ( monday) on Gov's Island? Thanks for any help.

[KarmaGirl]

I've something similar. Finally figured out that it was a blocked air intake to the carb. Like a vapor lock in a choke. You could try Andrew's Marine at 875-0654. Tel him Marty (Karma) sent you.

[NoBozo]

OK: I'll assume you have a four cylinder Mercrusier...135 Hp at the prop. (depends on the year) Earlier years were HP rated at the flywheel. Later years were rated at the prop. I'm not sure..but I think the transission came around 1993. You seem to be pretty savy with motors.

Faulty ignition coils can overheat and short out internally....Then recover when they cool off. They are usually bolted in direct contact (steel to steel) with the engine block OR intake manifold, as in the V8s. This contact contributes to the coil overheating. Replace the coil. :) NB

EDIT: Running fine at the dock is NOT the same as running fine under load..underway.

[jt3kids]

thats what I was thinking, so as soon as the engine died, I grounded out the coil and cranked the engine. Spark came out perfect. And i did this within 5 seconds after it died, so it should still be hot...I was hoping I wasn't getting spark, but I was

[NoBozo]

There's Spark..and then there is SPARK. NB

PS: What year is your engine..?? just wonderin..

PPS: You said you grounded out the coil..does that mean you took the coil exit (center) WIRE and "touched" it to the block to see a spark...??

If thats the case..leave a sparkplug connected to a cylinder coil wire and ground the spark plug base.. to the block. Does the PLUG Arc..??

[bigdog]

I had same senario, however, I had a 4.3L Merc.....

Engine would run fine for 15-20 minutes then cough and stall....

After several trips to marina, and many dollars spent for things I didn't need performed, I found the underlying culprit either from NoBozo, DaveR,
Ishoot308, or SIKSUKR can't remember? Lot's of experience in this group for sure !

But the issue was the coil ! As NoBozo described so correctly quote.., '
Faulty ignition coils can overheat and short out internally....Then recover when they cool off'. This is 'exactly' what was happening.

Marina said it was gas related (ethanol), but after draining the tank, then filling with fresh gas, didn't resolve the issue. They then did a carb rebuild, again, didn't resolve the issue $$$.

After feedback from this Foum the common denominator was 'coil issue' ! I ordered a new coil for $35. and installed myself in about 30 min. Problem solved ! And the boat was running like a race horse again.

So, I still think you have a spark issue, as a result of a bad coil.

Oh, one last word, make sure you use a marina with a good reputation, and not just 'parts changers', who try this and that, as a process of elimination to resolve the issue.... Lessons learned !

Bigdog

[jt3kids]

Yes. I took of the middle plug of the distributor and went to frame. Seems like a good spark. I compared to the spark when it was running, and seemed to be the same. White/yellow look? Not blue... I called thurstons, and they don't have one. neither does NAPA. I will try some other places in the morning and try replacing myself. The coil I got a few months ago from the auto parts store. If that doesn't work, I will call someone in. I don't know what else to do.. thanks for ALL your information. I'll keep you posted.

[NoBozo]

Yes. I took of the middle plug of the distributor and went to frame. Seems like a good spark. I compared to the spark when it was running, and seemed to be the same. White/yellow look? Not blue... I called thurstons, and they don't have one. neither does NAPA. I will try some other places in the morning and try replacing myself. The coil I got a few months ago from the auto parts store. If that doesn't work, I will call someone in. I don't know what else to do.. thanks for ALL your information. I'll keep you posted.

You need a coil that will be compatible with a "Thunderbolt IV" ingnition module. NB

EDIT: I don't think NAPA will do it this time. Take a plug out of the cylinder ON the wire...and ground the base..crank it over....SPARK...??

[bigdog]

Hey...

I usually NEVER endorse any marine parts suppliers, but have great luck with the following:

Go2marine:
(Here's a coil for under $30, Thuderbolt for Merc, just an example)
http://www.go2marine.com/product/83471F/ignition-system-coil-18-5438.html

Also have used:
Marine Engine: http://www.marineengine.com/
Marine Parts Plus: http://www.marinepartsplus.com/aboutus.html

All with very competitive prices, good customer service, and fast delivery.

Good luck !

Bigdog

[jt3kids]

its an 89'.

[Dave R]

Make sure the ballast resistor is in place. Some people remove them thinking they will get a better spark. This makes the coil run too hot. To verify, measure the voltage at the coil. You should have around 9 volts (if memory serves) at the coil + lead when the engine is running.You don't want 12 or more volts at the coil, it's not designed for that much voltage.

Check to see if you have an exhaust leak. This can fill the engine compartment with CO (carbon monoxide) after awhile and that does support combustion like O2 (oxygen). Once you open the hatch to troubleshoot, you let fresh air in and the engine will run fine again. Try running with the engine hatch or cover open and see if it stays running.

[Dave R]

Couple of other things to check:

If the engine has points, replace the condensor.

Verify that the battery has good coennections at the battery and the engine. A loose connection can cause this problem.

Verify that the fuel line (especially the metal portion) does not contact the engine anywhere except at the pump and carburetor.

Replace the fuel filter in the carburetor, if equipped.

[Dave R]

While you have the engine hatch open, check the wiring on the coil.

On the + side, you should only have the purple resistor wire, and a purple/yellow from the starter.
On the - side, you should have a gray wire for the tach, and a black wire from the distributor. The OEM harness a white/green wire is spliced into the gray wire and goes to the shift interrupt switch.

[jt3kids]

update. got another coil today from Fays, same problem
new batt this year with all new wiring
new starter
new solenoid
new fuel/water filter yesterday
fuel additive
new wires, plugs, condenser, points, cap/rotor this year
Have done all troublshooting with hatch open.
new 130 T-stat last week
new hoses, water pump rebuild
new gimbal, U-joint, gaskets, etc lower unit

started it up right away this morning, ran fine for 10 mins, then shut off. tank vent tube clear.

I had it on a lake last friday, and it lasted for about 45 mins pulling kids on tube. Now it won't last more than 10 minutes.

[NoBozo]

its an 89'. OK: I looked it up. 1990 was the first year Merc started rating horsepower at the prop. Your motor should be 130 HP with an Alpha 1 with a gear ratio of 1.98:1.

Clymer has a nice repair manual for the 1986-1994 Mercruiser Sterndrive. I got mine at West Marine. :) NB

[NoBozo]

update. got another coil today from Fays, same problem
new batt this year with all new wiring
new starter
new solenoid
new fuel/water filter yesterday
fuel additive
new wires, plugs, condenser, points, cap/rotor this year
Have done all troublshooting with hatch open.
new 130 T-stat last week
new hoses, water pump rebuild
new gimbal, U-joint, gaskets, etc lower unit

started it up right away this morning, ran fine for 10 mins, then shut off. tank vent tube clear.

I had it on a lake last friday, and it lasted for about 45 mins pulling kids on tube. Now it won't last more than 10 minutes.

If you are always using the boat in fresh water, I would UP the T-Stat to 165. Don't know what else to tell you. :look: NB

[Winnaholic]

You really need to find out which it is, Fuel or electrical otherwise you will just be replacing good parts for a lot of $$ with no solution.

Take it out again with a can of carb cleaner or ether (be real carefull and keep fire extingisher handy), with engine hatch open run it till it stalls then give it a shot of carb cleaner or ether if it doesn't start you have an electrical problem.

If it is electrical you need to trace the power from the coil backwards to the ignition. I would bet on a older boat that if it's electrical it is corrosion or bad connection (assuming coil is good since you have already replaced it).

If it's fuel has the tank been drained, this ethanol crap has really caused a lot of similar problems on older boats. When was the last time the boat was used or run for a longer period of time, has it been sitting long?

Just one man's opinion

[Irrigation Guy]

If it's fuel related it could be the check valve fitting on the tank(easy fix). Assuming you say clear hose on vent to verify it doesn't have a low spot and fuel accumulated causing a vent issue. Open the fuel filler cap and then try it immediately after it quits.

[jt3kids]

UPDATE. I was a little wrong with what I thought I did. I didn't use an external tank until this morning. I found the problem. Something was clogging the fuel pick-up in the tank. The anti-syphon seemed fine, but I pulled out the tube from the tank ( something fell off and stayed in the tank). Maybe it was some sort of filter/screen, that was clogged. Got a new fuel pickup at Fay's, cleaned anti-syphon and worked perfect all day. On a sad not, my little 89' larson 170 is too small for this lake:(. It gets a little hairy out there with 8 people. I get tossed around pretty good. Looks like I'll need to upgrade next year before the family vacation. On another note ( and I'll post on another forum), but looking to head out to Weirs for a while. Where would I dock the boat for a few hours? do I have to call ahead? Is there a fee? Thanks again for all the advice

[Woodsy]

You can park at the Weirs town docks..... no fee and definitely no problem tonight. No need to call ahead.

On another note.... 8 people in a 17' boat! WOW!!!

[jt3kids]

yes. 6 of them kids. but even so, it was a struggle. the boat can do it, but the waves kill us. can't really get on plane with waves that big. just hoping to find some places to pull kids on tube for a couple hours a day. trying to stay close to the island..

[NoBozo]

UPDATE. I was a little wrong with what I thought I did. I didn't use an external tank until this morning. I found the problem. Something was clogging the fuel pick-up in the tank. The anti-syphon seemed fine, but I pulled out the tube from the tank ( something fell off and stayed in the tank). Maybe it was some sort of filter/screen, that was clogged. Got a new fuel pickup at Fay's, cleaned anti-syphon and worked perfect all day. On a sad not, my little 89' larson 170 is too small for this lake:(. It gets a little hairy out there with 8 people. I get tossed around pretty good. Looks like I'll need to upgrade next year before the family vacation. On another note ( and I'll post on another forum), but looking to head out to Weirs for a while. Where would I dock the boat for a few hours? do I have to call ahead? Is there a fee? Thanks again for all the advice

Okey Dokey.... NB

[jt3kids]

Hey NB. why up the T-stat to 165?. just curious. original equipment is 130. thanks, Jim

[MDoug]

yes. 6 of them kids. but even so, it was a struggle. the boat can do it, but the waves kill us. can't really get on plane with waves that big. just hoping to find some places to pull kids on tube for a couple hours a day. trying to stay close to the island..

We upgraded to a 22' C-Dory and can handle almost all conditions on the lake. A 25' would be even better, imho.

[Dave R]

UPDATE. Got a new fuel pickup at Fay's, cleaned anti-syphon and worked perfect all day. On a sad not, my little 89' larson 170 is too small for this lake:(. It gets a little hairy out there with 8 people. I get tossed around pretty good. Looks like I'll need to upgrade next year before the family vacation.
Glad you got it fixed; it's good to be handy...

Sorry to say, you picked pretty much the worst possible place on the lake to vacation with a 17 foot boat. There's an awful lot of boat traffic and wake chop where you are. If you were staying in Moultonborough Bay, you'd be much happier with the boat, I suspect.

[NoBozo]

Hey NB. why up the T-stat to 165?. just curious. original equipment is 130. thanks, Jim

RAW water cooled boats run in salt water are usually run with a low temp T-Stat..say 140 because if you run them hotter than that (ie Raw Water Cooled) you will likely Salt Up the cooling passages in the engine which is not good.

MANY people with boats used in salt water order the boat NEW with Closed Cooling...or retrofit it soon afterward. This system is also pressurized like your car, and can run hotter without boiling the coolant. The cost used to be something like $2K or more. The engine never sees salt water....just fresh water and anti freeze in the block. There is a heat exchanger to get rid of the heat.

ALL this allows the engine to run hotter which is MUCH more efficient..AND Best of all...the engine will not wear out nearly as fast as running it COLD. Your modern automobile typically runs at 187-190 degrees F.

If your boat came with a 130* T-Stat, it may have been originally sold by a dealer near salt water.

My 1986 Mercruiser V8 is run in salt AND fresh water with a 165* T-Stat. HOWEVER: After each salt water use, the boat is hauled out on the trailer and the system is Flushed with fresh water. The boat never stays overnight in salt water.

Having the Luxury of running your boat in fresh water ALL or most of the time, it just seems logical to take advantage of that. :D NB

[jt3kids]

Thanks all. Just got back from vacation. The boat ran fine the rest of the week. mornings, and early evenings where the best for the little old boat. Kids still had a good time though. we got down to Alton sand bar, and up to Meredith. Didn't travel across the lake though. Maybe next year. My son was impressed with all the Formulas, Baja's, Cigarette boats. I posted a new thread on another post, but any Ideas on an upgrade for next year? I can sell mine for about 2800, and I'd invest about 5000. What can I get for about 8000, that is small enough to tow to a local lake, but also handle Winnipesaukee? Possibly a bowrider that can handle about 8 people? Thanks for any advice.

[Dave R]

Thanks all. Just got back from vacation. The boat ran fine the rest of the week. mornings, and early evenings where the best for the little old boat. Kids still had a good time though. we got down to Alton sand bar, and up to Meredith. Didn't travel across the lake though. Maybe next year. My son was impressed with all the Formulas, Baja's, Cigarette boats. I posted a new thread on another post, but any Ideas on an upgrade for next year? I can sell mine for about 2800, and I'd invest about 5000. What can I get for about 8000, that is small enough to tow to a local lake, but also handle Winnipesaukee? Possibly a bowrider that can handle about 8 people? Thanks for any advice.

I went for a spin on Winni in a 2004 Glastron 195 on Friday. Handled the wake chop pretty nicely. I imagine a 19 foot boat would be in your price range, OK for much of the lake on decent weather/low boat volume days, and still be easily trailered. Wait until after Labor day for the best prices. For the rougher days, 23 feet is about the minimum you could operate on-plane most of the time. That size represents a big jump in tow vehicle requirements and price though.