30hp Mariner is skipping when I run W.O.T

[Johnshan1]

This is a 1986 30hp Mariner <br /><br />When I take the boat out with 3 people on board, we get 20 mph for the first 3 or so miles out, then all of a sudden the engine bogs a little and we are down to a top speed of 16 mph for the rest of the day.<br /><br />The top plug looks perfect, the bottom looks ok- looks like it may be a touch too lean. <br /><br />This is a new powerhead, just checked the compression and it is perfect on both.<br /><br />Carb was just cleaned when we did powerhead a month and a 1/2 ago.<br /><br />Any ideas? I can run it at WOT but the engine has a little skip/hesitation once every 3 seconds or so, it doesnt sound like its cutting out, just losing power- its not enough to slow the boat it just sounds like its skipping.<br /><br />Also if I pump the fuel primer it does no different.<br /><br />where do I start? thanks everyone.<br /><br />-John

 

[Johnshan1]

Re: 30hp Mariner is skipping when I run W.O.T

Also sometimes it will come back and we will hit 20 mph for a second and then it will go back to what it did before.<br /><br />Cooling system is fine also, the engine is not overheating. <br /><br />It idles perfect and I can troll for miles on end.<br /><br />I replaced everything in the ignition circuit but the CDI box when I did the rebuild as well (they were damaged).<br /><br />-John

 

[The Marine Doctor]

Re: 30hp Mariner is skipping when I run W.O.T

Is the fuel tank venting properly?<br /><br />TMD

 

[Johnshan1]

Re: 30hp Mariner is skipping when I run W.O.T

Thanks for the reply- yep I just went out and checked the vent line and it is free from kinks or twists, everything seems good. Vent line and gas line were all replaced when power head was done. <br /><br />Keep the comments comming, ive run out of ideas.<br /><br />Oh, I also just changed the fuel filter with no difference noted.<br /><br />-John

 

[heatherjoy]

Re: 30hp Mariner is skipping when I run W.O.T

This must be a tough one... anyone else?

 

[The Marine Doctor]

Re: 30hp Mariner is skipping when I run W.O.T

This is just a guess.<br /><br />Its possible that the High side of the stator is cutting out.<br /><br />Does your stator have RED and BLUE leads?<br /><br />TMD

 

[Johnshan1]

Re: 30hp Mariner is skipping when I run W.O.T

I dont think there is a stator-<br /><br />I have a impulse coil, and an igniton coil under the flywheel, thats it- and I replaced those. <br />correct me if i am wrong, thanks<br /><br />-John

 

[Johnshan1]

Re: 30hp Mariner is skipping when I run W.O.T

bump