Easy to Start, Idle Good, No Power

[Bateau]

Hi I have a 40HP Outboard Mariner 1989 who is do not deliver the asked power.<br /><br />This boat was is storage for about 5 years, it this time everything was fine. We decide to use it again (child, fun, etc). We ask our boat service center to do a big maintenance to make sure everything ok before going further.<br /><br />At your surprise, the engine start easier than is was in the past, but when we ask for power it just move forward like a boat full of water with an isle attached at the back doing waterskiing.<br /><br />I did change the fuel for higher octane possible and also change the spark plugs.<br /><br />Is anyone have an idea, it will be welcome...<br /><br />Thanks<br /><br />Bateau<br />(Means boat in French!!!)<br />

 

[ShafferNY]

Re: Easy to Start, Idle Good, No Power

Change back to a lower octane. The higher the octane number the slower it ignites, therefore it will ignite late in the cylinder as the piston is already on it's way down, not getting the full power possible. It more or less throws your timing off.<br /><br />Let us know what happens.

 

[Chris Wilson]

Re: Easy to Start, Idle Good, No Power

What work was done as part of the "big maintenance". If we knew that, and can assume they did a decent job, we might have a starting point.<br /><br />What maintenance did they do to your motor?<br /><br />Also, you need to provide more information about the motor itself. Take a look at and follow the posting hints in this site and it will help us.

 

[12Footer]

Re: Easy to Start, Idle Good, No Power

Does the engine reach it's full revolutions? Does it sound high, but just crawls forward? If so, the hub has spun in the prop. Remove the prop and take it to a prop shop to have a new hub pressed into it.

 

[JB]

Re: Easy to Start, Idle Good, No Power

Howdy Bateau.<br /><br />If you haven't spun the prop you are running on one cylinder.<br /><br />Disable each spark plug, in turn. If there is no change you have a dead cylinder. Check for a hot, blue spark.<br /><br />If you have good spark to a dead cylinder, squirt some fuel into the carb and see what happens.<br /><br />Let us know what you find.

 

[Bateau]

Re: Easy to Start, Idle Good, No Power

Hi All,<br /><br />12Footer: Is any way to convience the workshop of this problem (hub and prop) like turn the prop by hand will be easy, stiff, loose, shaky??<br /><br />JB: I got blue sparks for each 4 spark plugs. The sound do not change when I disconnect one of them at the time!<br /><br />Any other ideas... the workshop will be at my place end of the week and more info I get easy I will able to have it fix...<br /><br />Thanks all

 

[Bateau]

Re: Easy to Start, Idle Good, No Power

Hello All,<br /><br />First I want to thank you all for your great ideas.<br /><br />We finally found the problem and fixed it this week-end. It was the lower caburator who did not open. In idle mode this engine runs on 2 cylinder (1 carburator), when we engage the engine forward to lower carburator open and then switch to 4 cylinders. A little steel piece was missing in the plastic rod between the carburators.<br /><br />Alain Normandin.<br /><br />What a power for Mariner 40HP Magnum with a 15 feet fish boat!!!