Mercruiser 165 IL6 bogging and left me stranded

[79Renken]

Looking for a bit of advice here. My 1979 Renken with the 165 HP inline 6 has been giving me problems this fall.

We haven't been out this year until fall. The engine would start and idle just fine but stalled as soon as I exited the marina no wake zone and accelerated. I was able to get it restarted and idle back in. I found I had some water in my fuel and added a Moeller fuel water separator. I also found that the O-ring on the fuel cap was rock hard so I added a new O-ring. Pretty sure this was the source of the water.

I ran the boat on the muffs for a while, emptied filter and there was a little water. Took the boat back out and was able to accelerate and get on plane for a couple of minutes, then it stalled. I was able to limp in and when I dumped the filter it was full of water. I decided to replace the anti-siphon valve and fuel line from tank to pump. Also replaced the filter in fuel pump and carb inlet. I used an electric pump to pull the fuel out and this time very little water.

Yesterday we went out and I thought I had the problem solved. She accelerated and ran at cruising speed for about 30 minutes. Then she started to bog again and finally stalled. I emptied the filter and there was just a tiny bit of water in it. But I couldn't get it restarted. She would fire with starting fluid but no fuel was getting to the carb. The fuel filter canister never filled up. I had to be towed in for the first time.

I decided that the fuel pickup may be clogged. So today I emptied the tank with the electric pump. I pulled it all out through the fuel water separator. I had a strong flow of fuel and when the tank was emptied the fuel filter canister was clean fuel, no water.

My question, does this sound like a problem with the Mercruiser mechanical fuel pump? Or should I still look to issues with the tank? I'm now leaning toward the fuel pump, but before I replace it I hoped to get a second opinion. Since the tank emptied so easily through the tank fuel pickup, fuel line and fuel water separator I'm now leaning towards the fuel pump.

Any advice welcome.

Thanks

Jim

 

[Another retired guy]

Re: Mercruiser 165 IL6 bogging and left me stranded

Hi. Yeah, based on the symptoms you describe, I'll lean the same way as you - sounds like the fuel pump! A healthy pump should have no problem drawing fuel through that filter canister.

 

[bonzoscott]

Re: Mercruiser 165 IL6 bogging and left me stranded

Welcome to iboats! Based on the amounts of water you've found - Drain the tank and/or add a bottle of dry gas. There could be pockets of water all over the bottom of the tank. When you raise the bow, they collect at your pick up. Clean / change the filter at the inlet to the carb. Pull the line at the carb (engine off) and crank the motor to see if fuel is gushing out. You could do this before or after other steps, but I would dry gas and change filter at carb anyway.

 

[CaptainMak]

Re: Mercruiser 165 IL6 bogging and left me stranded

Take a 3 gal canister of fresh fuel and run it directly into the carb. See if that solves your problem.

If not, some stores loan fuel pressure testing tools. Measure the fuel pressure the pump puts out.

 

[harleyman1975]

Re: Mercruiser 165 IL6 bogging and left me stranded

I'm gonna say just change the fuel pump and scratch that off the list of possible sources of the problem. I know they are a buck and a half but still it might save you a ton of headaches.

 

[79Renken]

Re: Mercruiser 165 IL6 bogging and left me stranded

Thanks for the advice all! I have a fuel pump ordered, $97 from O'Rielly for the marine version. Replacing all filters and rebuilding my carb.

After pumping all the fuel out through the fuel pickup and water separator I put fuel line down through the fuel fill to completely empty the tank. I raised the bow and with the electric pump I pulled about another gallon of water which contained about 1/4 cup of water.

Hopefully this will cure my problems and I can enjoy the last warm days here. I'll post an update.

 

[CaptainMak]

Re: Mercruiser 165 IL6 bogging and left me stranded

sure is one expensive way to fix boats: guessing. Hope this does the trick.

 

[harleyman1975]

Re: Mercruiser 165 IL6 bogging and left me stranded

I prefer to call it process of elimination

 

[Silvertip]

Re: Mercruiser 165 IL6 bogging and left me stranded

A very simple pressure/vacuum tester from any auto store would eliminate any guesswork regarding the fuel pump. TEST IT. You can even test it without a test setup other than an empty gallon jug. Remove the line at the carb. Put it into the gallon jug. Spin the engine over. If you get a good solid stream you have a good pump and still have $97 to spend on -- well -- whatever. But since you continually sucked water from the tank that very likely was the problem. Did you add a fuel system additive as was suggested.

 

[79Renken]

Re: Mercruiser 165 IL6 bogging and left me stranded

Ok, I did replace the fuel pump. But it was a very old pump so I don't feel too back about replacing it. The old one would provide a nice flow of fuel and as I said above I cruised for about 30 minutes before the problem occurred. I thought possible worn or one of the check valves was sticking/clogged.

So to repair I:

-replaced fuel pump.
-new fuel filters throughout
-rebuilt carb
-cleaned spark arrestor
-rerouted fuel line from tank to fuel/water separator (shorter with less bends)
-emptied fuel tank
-started with fresh fuel
-added a bottle of Heet in case there was a tad of water left in the tank

this past Spring I:
-replaced distributor cap
-replaced points and condenser
-new spark plugs


Took her out for a test run this afternoon, started quickly, cruised at full power for about 10 minutes... then bogged and lost power. I was able to restart and it would cruise at speed for a couple of minutes then bog and lose power. She restarted every time, but full power would only last a minute or so and seem to get shorter as time went on.

I stayed close to the marina and idled back in with no problems. Never stalled idling in and restarted and loaded on the trailer with no problems.

So now I'm stumped. Should I get a fuel pressure gauge and test? I have my doubts that would show the problem as I can cruise at full power for 10-30 minutes before having problems. Is there something electrical? I tried a coil I had in my garage when having this problem a couple of weeks ago, but at that point I didn't have all the water out of the fuel (could have been multiple problems confusing the issue at that point???).

Any advice welcome!

Thanks

 

[searay3]

Re: Mercruiser 165 IL6 bogging and left me stranded

When it dies you need to check if your losing spark or fuel. Had a similar issue once and after chasing ghosts and spending a good deal of cash came to find out the coil was bad and quit when it heated up. If the spark is still there, try the remote tank test. There is no good way to test a coil that I have ever had luck with. Coils are on the cheap side if it's old. Mine was original and 15 years old when it finally failed.

 

[CaptainMak]

Re: Mercruiser 165 IL6 bogging and left me stranded

save yourself the headaches and aggregation and purchase a pertronix 2 and flamethrower coil setup. the best money you'll ever spend on ignition.

 

[79Renken]

Re: Mercruiser 165 IL6 bogging and left me stranded

When it bogged the boat dropped off plane, however if I cut the throttle back the engine would continue to run and not die. I could then apply power and she would run at power on plane for a minute or so. To me that sounds like it's got spark but is starving for fuel. Does this seem right?? Or could a bad coil be delivering a weak spark and cause these symptoms?

 

[bonzoscott]

Re: Mercruiser 165 IL6 bogging and left me stranded

Recreate the problem on the lake and then use a spark tester to see if there is spark. Coil heats up and fails. You could just replace the coil $25-$50, depending. If that's not it, check the anti-siphon valve at the tank. I don't understand how you "pulled another gallon of water which contained about a 1/4 cup of water".

 

[79Renken]

Re: Mercruiser 165 IL6 bogging and left me stranded

Recreate the problem on the lake and then use a spark tester to see if there is spark. Coil heats up and fails. You could just replace the coil $25-$50, depending.

When it bogged on the lake the engine didn't quit, just lost power but would still idle as long as I backed off the throttle quick enough. Otherwise it would start right up. Isn't this a pretty good indication there is spark? Would a spark tester show a weak spark versus a normal spark? Does a problem coil exhibit these symptoms?

If that's not it, check the anti-siphon valve at the tank.

The anti-siphon valve was just replaced.

I don't understand how you "pulled another gallon of water which contained about a 1/4 cup of water".

I emptied the tank through the fuel lines and water separator with an external electric fuel pump. Then to get anything in the bottom of the fuel tank below the fuel pickup I inclined the boat bow up, used the electric fuel pump by sticking fuel line down through the fuel filler opening to get the very bottom of the tank. Since water rests on the bottom of the tank this was to get the last of the water, which was about 1/4 cup of water in the last gallon.

 

[pilot4net]

Re: Mercruiser 165 IL6 bogging and left me stranded

Sounds like the engine is starving for fuel. It sounds like as you run for some time, the fuel tank encounters a vacuum condition from which the fuel pump cannot draw adequate fuel against. I'd do more checking on the fuel system...

 

[79Renken]

Re: Mercruiser 165 IL6 bogging and left me stranded

Problem solved! Finally.

Now that the weather has cleared I decided to replace the coil. From reading other threads it sounded like a coil issue. I had previously swapped the coil for one I had laying around the garage, however at that time I was still having major issues with water in the fuel which are now resolved.

It still seems odd that the engine would lose power but not completely die with the bad coil. But the symptoms matched as it would run well at first then when the problem occurred it would have power for a shorter and shorter amount of time.

I cruised today for a bit over an hour without any issue. The engine seems to have more power and is more responsive. I sure wish the coil would have died completely as intermittent issues are a pain to solve.

Thanks for the advice all.

 

[PBarrett]

Re: Mercruiser 165 IL6 bogging and left me stranded

Glad you finally solved your problem. I had the same thing happen to me on my 5.7. I too finally changed the coil and got back on the water. one day I had my boat tied up at the dock with the engine running and lifted the engine hatch and went to move my trim tab hose and my arm touched the coil, got a real painful burn on my arm from the coil. I ended up replacing the new coil with an epoxy filled sever duty coil, haven't had any problems since.The coil I used was an Accel coil from Summit racing. I wasn't looking for a high performance coil,but it was the only epoxy filled coil I could find. Now that you got it running, go run the hell out of it.

Pat