I have a H25 with a motorwell. Last year was my first year with the boat and I used a 6hp chrysler motor. It would die down at high rpms. I figured I needed a more powerful motor. I replaced it with a 15hp chrysler this year. This motor has more power but eventually it dies down and stalls. I am having the same problems!! I have cleaned the carb, replaced the reed valve gaskets(one was leaking a little), replaced the points, and plugs. Exhaust fumes do bubble up into the well when we are not moving but under way there are no fumes in the well (I even have the upper exhaust ports vented out throught the transom), maybe the motor is not getting enough O2. The spark plugs appear to somewhat responsible but I am out of options on what to do differently. They both have good spark, they are the hottest NGK plug available (BP6HS not the recommended BP7HS). The upper cylinder's plug does get a little more carbon on it the the lower cylinder(the lower plug is a little wetter when it is removed) but the carbon can be wiped off with a towel. Compression is even between the two cylinders (70 psi cold/dry). When the engine stalls if I open the throttle all the way and choke the motor it will putter and die, the I turn off the choke and three pulls later it starts, if I rev the motor up and down after about six revs it will run OK for a minute then die again. I can run the engine for hours by using this technique, once it is running and starts to die down, pinch the fuel line and wait, as soon as the motor revs up unpich the line and repeat. Thinking the motor needs to be running a leaner mixture I have replaced the jets, I am running the smallest jet with no big improvement. If I lean out the idle mixture needle it will not run at low rpms(kicks and dies). Thinking the exhaust ports where clogged I removed the head and cleaned the tops of the pistons and veryfied all of the tubes where free of obstructions(there was some carbon on the pistons but nothing serious). I am out of ideas, it is very frustrating to use this boat when I cannot rely on the engine. I need to use an older chrysler engine because nothing else fits in my motor well. Open to suggestions. Dan
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under what conditions!
Dan: When you say running the engine, are you in gear and driving the boat or is this just at the dock (in neutral). The reason that I'm asking this was because if you have a motor in a well and are driving the boat the stern will sink lower in the water. The faster you go the lower the stern will be and you may be not getting enough air? Is this a possibility?
Dan: When you say running the engine, are you in gear and driving the boat or is this just at the dock (in neutral). The reason that I'm asking this was because if you have a motor in a well and are driving the boat the stern will sink lower in the water. The faster you go the lower the stern will be and you may be not getting enough air? Is this a possibility?
Air does sound like the problem.
Those symptoms are sure indicative of lack of air as Steve points out. My outboard experience ended about 20 years ago so I am not familiar with current technology. What kind of air intake and filtration is used? Is there some way to duct fresh air in?
Those symptoms are sure indicative of lack of air as Steve points out. My outboard experience ended about 20 years ago so I am not familiar with current technology. What kind of air intake and filtration is used? Is there some way to duct fresh air in?
The motor is an '84 Chrysler 15hp
The motor is an '84 Chrysler 15hp(nothing hightech)magneto, points and no air filter. I cut a hole in the top of the motor cover and glued a 2 1/2" pvc Elbow onto it to get more air into the engine. The front of the well has a 1' x 1' opening into the cockpit and the back of the well has two 2" vents, but it does get smoky in there when it is in nuetral. I just don't understand why it happens when we are underway and in gear, the fumes are all sucked out the lower unit and away from the boat? Dan
The motor is an '84 Chrysler 15hp(nothing hightech)magneto, points and no air filter. I cut a hole in the top of the motor cover and glued a 2 1/2" pvc Elbow onto it to get more air into the engine. The front of the well has a 1' x 1' opening into the cockpit and the back of the well has two 2" vents, but it does get smoky in there when it is in nuetral. I just don't understand why it happens when we are underway and in gear, the fumes are all sucked out the lower unit and away from the boat? Dan
Dan, You said that your motor has an older
style ignition system, as in points and condenser. I assume the points are set corectly and have no pitting or smoked appearance. If they do then they need replacement. Now the important point. I have seen throughout my mechanical career many times that the condenser goes bad and can cause a similar condition. This is fairly rare but not uncommon, even a new condenser. This can be eliminated as the cause if both the new and old condenser did not change the problem. But, be very certain that the points and condenser also have a very clean and solid connection with the base mounting plate. The rotor and cap should also be is serviceable condition. Another problem source is very possible the air correction jet in your carb. I would say that 80 to 85% of the persons overhauling carbs have no idea of its function or presence. Since you have changed your fuel jets and had no inprovement check this. Fuel jets really never go bad, they are just not right for the air condtions in different altitudes. Your earlier jets were not the problem unless plugged. The air jet is the condition I would verify first. Ray s/v Speedy
style ignition system, as in points and condenser. I assume the points are set corectly and have no pitting or smoked appearance. If they do then they need replacement. Now the important point. I have seen throughout my mechanical career many times that the condenser goes bad and can cause a similar condition. This is fairly rare but not uncommon, even a new condenser. This can be eliminated as the cause if both the new and old condenser did not change the problem. But, be very certain that the points and condenser also have a very clean and solid connection with the base mounting plate. The rotor and cap should also be is serviceable condition. Another problem source is very possible the air correction jet in your carb. I would say that 80 to 85% of the persons overhauling carbs have no idea of its function or presence. Since you have changed your fuel jets and had no inprovement check this. Fuel jets really never go bad, they are just not right for the air condtions in different altitudes. Your earlier jets were not the problem unless plugged. The air jet is the condition I would verify first. Ray s/v Speedy
Fuel flow prob?
Dan, this is a stretch and I have no outboard experience but in as much as these symptoms have occured on two separate motors it remined me of a problem I had last year on my 36 HP Yanmar. It would stall under power, any thing over 2800 RPM my cruising speed. I changed the primary filter, no luck, then the secondary fuel filter, same results, then microfiltered the diesel fuel, no good. It turned out that I had a blockage at the bottom of the pick up tube in the fuel tank. There was a screen at the bottom and it was partially clogged. The engine would run fine at idle but under load when more fuel was demanded, it starved. We cleaned the screen (and now I add a biocide to keep stuff from growing in my diesel) and things have been fine. Maybe you have a similiar fuel flow or tank problem, it seems odd that this would happen to two different engines. Hope this helps Good Luck Tom LaRocco SV Follow the Sun H376
Dan, this is a stretch and I have no outboard experience but in as much as these symptoms have occured on two separate motors it remined me of a problem I had last year on my 36 HP Yanmar. It would stall under power, any thing over 2800 RPM my cruising speed. I changed the primary filter, no luck, then the secondary fuel filter, same results, then microfiltered the diesel fuel, no good. It turned out that I had a blockage at the bottom of the pick up tube in the fuel tank. There was a screen at the bottom and it was partially clogged. The engine would run fine at idle but under load when more fuel was demanded, it starved. We cleaned the screen (and now I add a biocide to keep stuff from growing in my diesel) and things have been fine. Maybe you have a similiar fuel flow or tank problem, it seems odd that this would happen to two different engines. Hope this helps Good Luck Tom LaRocco SV Follow the Sun H376
Fuel Line?
If you are using an external tank could the fuel line be collapsing and cutting off the fuel supply? Another thought, have you tried it in a tank to see if it is the well in the boat choking it out?
If you are using an external tank could the fuel line be collapsing and cutting off the fuel supply? Another thought, have you tried it in a tank to see if it is the well in the boat choking it out?
similar problems, no answers
I have been experiencing something similar on my 8hp 1996 mercury outboard. At full speed it runs fine for about 10 minutes, then it starts to stall and run very poorly. It doesnt cut off, but runs as if it is not getting fuel. If I pull the choke out, it runs fine. It also runs fine at idle speed. Any answers? david mosley, hunter 23
I have been experiencing something similar on my 8hp 1996 mercury outboard. At full speed it runs fine for about 10 minutes, then it starts to stall and run very poorly. It doesnt cut off, but runs as if it is not getting fuel. If I pull the choke out, it runs fine. It also runs fine at idle speed. Any answers? david mosley, hunter 23
Thanks for all the responses so far, But.....
When I cut the fuel supply off it runs great!! So it is getting fuel(too much? Then why does it need choked to start again?). The points and condensors are new! They are properly set. I ran it in a tank in March, after doing the piston work and replacing the reed valve gasket that was leaking. It ran fine (I thought I was out of the woods!) but it was not pushing a 25' boat. After I put the motor back in the boat I did not even go 20 meters and it started acting up again. Thanks for all the suggestions, keep em coming there has to be something that I have missed! Dan Pitman s/v Essayons
When I cut the fuel supply off it runs great!! So it is getting fuel(too much? Then why does it need choked to start again?). The points and condensors are new! They are properly set. I ran it in a tank in March, after doing the piston work and replacing the reed valve gasket that was leaking. It ran fine (I thought I was out of the woods!) but it was not pushing a 25' boat. After I put the motor back in the boat I did not even go 20 meters and it started acting up again. Thanks for all the suggestions, keep em coming there has to be something that I have missed! Dan Pitman s/v Essayons
This sounds a LOT like an air problem...
This is strictly a guess, but... Since the only place your motor seems to have this problem is in the motor well, I would have to guess that the motor is getting oxygen-starved by exhaust gasses in the motor well. Are you sure that the carb is getting plenty of fresh air, and not sucking in exhaist gasses? Can you run the motor with the lid to the motor well open? If so, does the problem persist? --Jon Bastien H25 'Adagio'
This is strictly a guess, but... Since the only place your motor seems to have this problem is in the motor well, I would have to guess that the motor is getting oxygen-starved by exhaust gasses in the motor well. Are you sure that the carb is getting plenty of fresh air, and not sucking in exhaist gasses? Can you run the motor with the lid to the motor well open? If so, does the problem persist? --Jon Bastien H25 'Adagio'
Fuel tank?
If both engines have the same or similar problem, I would change the fuel tank if you are using the same one, and also replace the fuel line and priming bulb because there may be a problem with that. Be sure the air valve is open! I often forget.
If both engines have the same or similar problem, I would change the fuel tank if you are using the same one, and also replace the fuel line and priming bulb because there may be a problem with that. Be sure the air valve is open! I often forget.
Talked With a Buddy of Mine
He suggested three things 1. Compression is on the low side though he said he has seen them run lower 2. Try running with the engine cover off and the hatch open. He has put 3" bilge blowers on a couple of boats having the same problem to get more fresh air into the well. 3. The exaust ports maybe plugged up. Run some Quickleen or somthing similar through it and be sure to run OMC, Quicksilver or Yamaha oil with your fuel. I never thought it made a difference but he swears that it does.
He suggested three things 1. Compression is on the low side though he said he has seen them run lower 2. Try running with the engine cover off and the hatch open. He has put 3" bilge blowers on a couple of boats having the same problem to get more fresh air into the well. 3. The exaust ports maybe plugged up. Run some Quickleen or somthing similar through it and be sure to run OMC, Quicksilver or Yamaha oil with your fuel. I never thought it made a difference but he swears that it does.
Agree with John
The primer bulb has a one way "check" valve. I would replace the fuel line and bulb. Also make sure the fuel is fresh. Good Luck, Bob
The primer bulb has a one way "check" valve. I would replace the fuel line and bulb. Also make sure the fuel is fresh. Good Luck, Bob
Thanks for all the responses!
I have been leaning towards venting more fresh air into the motor well. Exhaust fumes in the motor well have been a problem in the past, that is why I vented the exhaust ports out the transom. Fumes still make it into the well from the lower unit. This is not a fuel delivery problem, this engine gets enough gas. I have thoroughly cleaned the exhaust ports, I have used Seafoam and it did not make a big improvement. Replacing the rings might improve compression but I will wait to do that until this winter. The gentleman I bought this boat from never had it in the water. It sat in his yard for a few years ( a restoration project he never had time for). It would be nice to ask the previous owner what he did while under power. Thanks again for all the suggestions. If you have any more please let me know! Dan s/v Essayons
I have been leaning towards venting more fresh air into the motor well. Exhaust fumes in the motor well have been a problem in the past, that is why I vented the exhaust ports out the transom. Fumes still make it into the well from the lower unit. This is not a fuel delivery problem, this engine gets enough gas. I have thoroughly cleaned the exhaust ports, I have used Seafoam and it did not make a big improvement. Replacing the rings might improve compression but I will wait to do that until this winter. The gentleman I bought this boat from never had it in the water. It sat in his yard for a few years ( a restoration project he never had time for). It would be nice to ask the previous owner what he did while under power. Thanks again for all the suggestions. If you have any more please let me know! Dan s/v Essayons
chrysler
Dan, sorry to be responding so late, Buoyant his been out of her slip for the past week. ....... I once owned an '82 Chrysler 15hp engine, which I used to power a Metzler inflatable. It was, simply put, the worst engine I've ever owned. (And I've otherwise owned two Mercuries, a Suzuki, a Nissan and two Evenrudes.) I had problems with the Chrysler from the day I bought it, and took it from one mechanic to the next trying to find a fix. Hotter plugs, increased air supply, different jets, adjusting the magnito. Nothing worked. I ended up selling the Metzler, which I loved, because it was the only way I could find somebody to buy the Chrysler.
Dan, sorry to be responding so late, Buoyant his been out of her slip for the past week. ....... I once owned an '82 Chrysler 15hp engine, which I used to power a Metzler inflatable. It was, simply put, the worst engine I've ever owned. (And I've otherwise owned two Mercuries, a Suzuki, a Nissan and two Evenrudes.) I had problems with the Chrysler from the day I bought it, and took it from one mechanic to the next trying to find a fix. Hotter plugs, increased air supply, different jets, adjusting the magnito. Nothing worked. I ended up selling the Metzler, which I loved, because it was the only way I could find somebody to buy the Chrysler.
Motor stalling
Check your oil injector, see if there is any kinks, or leaks in the hose. I had a similar problem with a suzuki outboard put a new injector pump on it and never had the problem again.
Check your oil injector, see if there is any kinks, or leaks in the hose. I had a similar problem with a suzuki outboard put a new injector pump on it and never had the problem again.
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