should dwell go down when rpms go up

[lindb40530]

I have an 84 OMC 305 I/O. I have owned it since it was new and never had a problem. I repalced plugs, points, condensor, rotor and cap. I now can't get the boat over 2200 rpms. It runs fine till then and starts missing or bogging after that. I hooked up a dwell meter and the dwell goes down as the rpms go up. Is this normal, or could this be my firing problem. Specs say 28-32 dwell. It goes down to about 15. Thanks

 

[xltier]

Re: should dwell go down when rpms go up

ur dwell is a direct indication of ur point gap.if ur good at idle and it changes a lot when reved up,i cant think of anything other than a loose distibutor shaft bushing.grab the top of the dist. and pull it back and forth.u can set ur points with ur dwell meter also by having someone crank the engine while u turn the adjuster screw and watch the gauge.hth

 

[lindb40530]

Re: should dwell go down when rpms go up

I thought the same re: the bushing however, it fells solid to me. I took it out and am taking it to the shop tomorrow. I'll post what happens. I have rebuilt the carb, and changed out everything in the ignition system to no avail. It's driving me bannanas..... Thanks

 

[Boatist]

Re: should dwell go down when rpms go up

Lindy<br />Dwell should not change at all. I do not think my engine would even run at 15 degrees. First make sure it is not a problem with your meter.<br />Check the points spring tension and see if you can give it a little more tension and retest. Make sure you have a good ground to the points plate and points. Put a drop of light oil on the points pivot point. If it has a cam wiper/lube wick, pull it back some. Make sure the wires are clean and tight. Change the condensor again or put back the old.<br /><br />Please come back and tell us what fixes it.

 

[lindb40530]

Re: should dwell go down when rpms go up

I am an idiot. the distributor guy got a good laugh when he saw how I installed the points. On the prestolite distributor you have the tension bracket and the coper lead which gets screwed into the retaining screw with the condensor and negative coil wire. The points come with the tension bracket on the outside but should be mounted with them on the inside. <br /><br />Since I had it wrong, I had very little tension on the breaker arm. Thanks boatist. You had it right. The lack of tension caused the dwell to go down when the rpms went up.<br /><br />Hope my stupidity can save some one some heartache. I now have a rebuilt carb, all new fuel system and all new ignition components so it should run good for a while.

 

[Boatist]

Re: should dwell go down when rpms go up

Lindy<br />Thanks for the report and glad you got it fixed. I think it will help us all some day.<br />Have fun on your boat and enjoy.