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Ask The Motor Doc

Ask The Motor Doc
Ask The Motor Doc

Every month we post a new series of questions asked by our website visitors, with answers from our Motor Doc, Grid Michal.




Motor Starved for Gas When Idling

Eric Ferrenbach, Collinsville, Illinois: "I've put up with this problem for several years and I'm hoping you can give me some advice. I have a Sprint Fish and Ski with a 150hp Johnson outboard (1999/2000?) and I've had this problem since I bought the boat new: The motor seems to be starved for gas when idling. It only happens after the engine gets warmed up, normally after we've been out running, gone slowly through the no-wake zone (without a problem), and then parked it at the dock while we have lunch. When we come back out we have a hard time keeping it running. It will begin to sputter and usually dies when we put it in gear. Pumping the ball helps a little bit but doesn't solve the problem. I've tried to uncap the gas tank thinking it may be some sort of venting problem, but that doesn't seem to help either. When the engine is cold it idles just fine. Any advice would be appreciated."

Well, my first thought is that the engine is really ticked that you aren't inviting it for lunch! You can begin some diagnostics by pushing in the primer (key) when the engine starts to falter. If the RPM pick up and the engine runs okay, then you've properly diagnosed that the engine is starving for fuel. At that point you can go to the dealer and ask him to reset the floats, or re-jet the carbs, or even look for an air leak when the engine's warm. I just fixed one where the throttle plate assembly behind the carburetors was warped just a tiny bit and allowed the engine to run lean (60-degree OMC). Start with that and see where it goes.























Starved for Fuel Revisited

John Jefferies, Fresno, California: "I have a 3.0L Volvo Penta engine in my 2003 Chaparral 180SS. In early June of this year I had the starter motor replaced under extended warranty. Ever since that time, the engine has quit between 3700 and 4200 RPM. When it backs off to around 3500 RPM, it starts running perfectly again. The mechanic at the Volvo Penta authorized dealership insists that there's no correlation between the starter problem and the current condition. I've checked the starter wiring against my shop manual and find no problems or incorrectly installed connections. I've checked for cracks in the distributor cap and the coil, checked the coil wire and spark plug cables and can find no problems. The distributor seems not to have a condenser inside, which was suggested as a possible problem. The points are okay and not burned or scorched. I've replaced both fuel filters (in fuel pump and at carburetor) and added a stabilizer to the fuel tank that would deal with any water accumulation. The engine just seems to be starved for fuel or spark in that narrow RPM gap. Help!"

The dealer is correct, there is no correlation between the starter problem and your current situation. If it were mine, I'd go to the source, the fuel pickup in the tank, and check the filter screen and the anti-siphon valve, both of which could cause your problem.

 

 

 

 

 

 

Starving for Fuel, Take 3

Alan Maher, Albany, New York: "I have a 1999 Johnson 175hp (carb'd) motor. When the weather is hot and humid, I can't keep the motor running. It idles fine but when I put it in gear, it misfires and stalls. It seems to be starving for fuel. I've been able to work through it by squeezing the primer bulb while it's idling. I'm running regular unleaded gasoline from a busy gas station, so I don't think it's bad gas. Any suggestions besides not fishing when it's hot and humid?"

That would be my first thought. That's why they have air-conditioned fish markets. Well, I'm thinking that your VRO isn't pulling fuel because 1) there's an air leak in the pulse hose/fitting; 2) one (or both) of the intake manifolds are warping as they warm up; or 3) whoever had his hands on the throttle linkage last didn't balance it after carburetor work.























Smoking Alot, Fuel in the Water

Luc Goulet, Fabre, Quebec: "I own a 1996 Johnson Fast-Strike 115hp. It runs well and starts good, but this year it has begun to smoke a lot, especially when we slow troll. I've also noticed fuel in the water, probably by the exhaust. What problem might that be indicating?"

Well, sir, you have about 10 years on that engine. I'm not sure how you service it, oil it, or if you run it hard and put it away wet, as the saying goes, but the spotting on the water is indicative of unburned fuel. The first thing I'd check is the compression and the spark plug wear. Then again, you may have the engine trimmed all the way in, and trimming it out just a little may cure the smoking and the fuel droplets. Try that first.























The Little Engine that Can't

Metello Levi, Toronto, Ontario: "I've got an old Johnson 6hp which I decided to put some money into last year. It ran fine until the last day of this year's opener when it stalled on me, and it hasn't run well since. I can get it started -- it revs well in neutral -- but when I put it into gear, it has no power and I have to run it wide open just to keep it running. I was able to get back to the launch with it, but it was real slow. The day before, I noticed a little bit of oil/water leaking out of it when I put it in the car. I assume the problem is in the lower unit, but I've never ventured into that realm. I'm pretty good at tinkering but have little experience with outboards and am hoping for some advice. Thanks."

Try changing the points and condensers -- AND the coils, if needed. It sounds as though it's running on one cylinder.

 

 

I Want to Premix My Own Fuel

David Springer, Bon Aqua, Tennessee: "I have a 1994 Tracker with a 40hp Evinrude. I want to unhook the oil injection and premix my own fuel. What's the easiest way to unhook or bypass the VRO system? Thank you very much for your help."

Unplug the oil hose at the cowl. Add a short piece of hose to the fitting at the cowl, then plug that hose off with a bolt, clamped in. Then use your pre-mix.

 

 

 

Boat Not Planing Quickly Enough

Benjy Milder, Kansas City, Missouri: "I have a 1986 18-foot Champion 181 Pro Bass boat with a 150hp Johnson motor. I just can't seem to get the boat to plane very quickly -- it takes 15-30 seconds, but when it does it really moves. I'm mainly concerned from a safety standpoint, as it really impedes my vision with the boat at a 45-degree angle. It has the in-boat gas tanks but I don't keep them very full; and even with my 280-pound fishing partner in the front of the boat, it still basically points straight up in the air. Is my motor just underpowered for the job? Would a different prop help at all, or is this a problem common to having a big bass boat?"

Obviously, I think that loading more weight in the bow will help cure your problem. If your engine is turning in the 5000-5500 RPM range, the engine's fine. Although I don't know that boat personally, an 18-foot boat with that much weight is probably stern-heavy and will continue to act as though it's the Discovery taking off from the Kennedy Space Center.























Problem with the Gear Module?

Francis Wurster Jr., Deptford, New Jersey: "I just purchased a 1987 Renken AFT with a Chevy 305. It had some minor problems that I got corrected, but I'm still having some trouble. Every time we attempt to take the boat out, it stalls. I gave it a full tune-up (plugs, wires, cap, rotor, points, and condenser) and also put some fuel stabilizer in the gas tank, because the boat had sat for about a year. The guy at my local marina said that it could be a problem with the gear module (is this the term for it?). He said it had something to do with the outdrive, which -- if the cables were not adjusted properly with the right tools -- it would cause the motor to shut off when opening the throttle in gear."

I think I understand what the guy was saying. There is a shift-interrupter switch that momentarily stops the engine while the gear selector is coming back to neutral. If that's sticky, yes, it could be shutting the off engine for too long, and stalling it. Probably, though, the carb has gum in the jets, and no amount of cleaner will work unless it's removed and disassembled.























Steering Locked Up (Readers, Please Help!)

James Parmenter, Hopewell, Virginia: "I have a boat with 1992 80hp Mercury outboard. I put the boat up for winter storage and left the motor in a down and straight position. After winter, I raised the motor to take out of storage and, while removing it from the building, the motor pivoted to the left. Now it's locked in that position and I can't move it by the steering wheel or by hand. I've disconnected the steering linkage outside of the motor, and the steering wheel turns okay but motor is still locked up. What could be the problem? Any help would be deeply appreciated. Thanks."

I don't have a clue! There's nothing in the steering system stopping it from turning, so where to look next? Readers…?

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