89 85 hp runs hard then slows, then runs hard again....power pack?

I've replaced the fuel pump diaphram, it has a new head gasket, new exhaust gaskets, new impellor, compression is 109/110/105, rebuilt carbs, adjusted mistures, when it runs well it accellerates hard (I mean powerfully) up to 5700 rpm (light load) and will run for many minutes like that.....until...well until its like I throttle back suddenly....rpms slow from 5700 to 4300 without moving the throttle....then its like throwing a switch......runs HARD for a few seconds, then slows, then hard, then slow....it never quits...it doesn't get rough....just slows mysteriously....because its so sudden when it happens I was wondering if it might be a power pack....what happens when they are on the way out<br />?.....thanks.......Tim

Re: 89 85 hp runs hard then slows, then runs hard again....power pack?

I would suspect old coils first, breaking down when they get hot.<br /><br />Does it ever happen when the engine is cold?

Re: 89 85 hp runs hard then slows, then runs hard again....power pack?

No it doesn't seem to happen when its cold, however I always let it run a couple minutes to warm up before I give it more than 1/2 throttle....If it is coils....are those the blue boxes on the rear right?.....do I replace em all, or just one at a time?....and how do I know for sure thats the problem (Iknow we never really know....but with a reasonable assurance)?....thanks for the help...Tim

Re: 89 85 hp runs hard then slows, then runs hard again....power pack?

Any more thoughts about this problem....should I head out and buy some power packs...where and how $....thanks.....Tim

Re: 89 85 hp runs hard then slows, then runs hard again....power pack?

Max rpm is 5500 on that motor. You may want to lower pitch by 2 on that prop.

Re: 89 85 hp runs hard then slows, then runs hard again....power pack?

I think you should set a dollar limit on how much you are willing to spend on this motor before you start buying parts.<br /><br /> click cd box and coils <br /><br />Number 45 and 46 in the list.<br /><br />Aftermarket parts may be available from maxrules.com

Re: 89 85 hp runs hard then slows, then runs hard again....power pack?

Since the problem is intermitant and the parts are very expensive is there some way I can confirm the packs are the problem without potentially buying new ones (there are 3) only to find the problem is elsewhere.....FWIW a dealer told me this motor is worth about $1000 Cdn so I really don't want to put $900 worth of powerpacks in it if I don't have too....I would rather sell it off and buy another......<br /><br />Thanks once again....Tim

Re: 89 85 hp runs hard then slows, then runs hard again....power pack?

Check www.standardmagneto.com/Marine/forceparts.html for OEM Force/Prestolite ignition parts at the lowest cost I've seen. They are based out of Chicago.

Re: 89 85 hp runs hard then slows, then runs hard again....power pack?

How do I test a powerpack?<br />I assume it's just one of the three thats failed (failing)?

Re: 89 85 hp runs hard then slows, then runs hard again....power pack?

The powerpaqck tests are quite involved, several pages of info in my Clymer repair manual. Much more than I can understand and interpret. You really should invest $30 in a manual before you get too far into this.

Re: 89 85 hp runs hard then slows, then runs hard again....power pack?

I don't think you're to the point of replacing powerpacks yet. If you were dropping ignition to one cylinder I would expect the engine to run rough when it slows down. <br /><br />You may still have a fuel problem. If the fuel flow was restricted you'd slow down and run evenly on all cylinders. The key is to determine if it's running on all cylinders when it slows down. If yes, it's probably a fuel delivery problem.<br /><br />As Roscoe said, it could be a bad coil. The coil is different from the ignition pack, and cheaper. <br /><br />I hate to start swapping parts without isolating the problem a little better. <br /><br />Most electronic components fail hard, they don't work intermittently unless there is a loose connection. Check and clean all the ground wires on the ignition board and the ground strap to the block. You'll have to loosen the board from the vibration isolators to check for bad grounds on the back of the board.<br /><br />Then if the probler persists, try to determine if only one cylinder is causing the problem.