79 Rude Performance Mystery

[BBMerlin5091]

Re: 79 Rude Performance Mystery

ok,....my timing light crapped out, so i'll have to buy another one and check the timing tomorrow. Quick question: this boat sat for roughly a year and a half without being started, i have done all of the general maintenance stuff, except for changing the thermostats, could the t-stats cause those two cylinders not to fire if the t-stats are stuck open? the water here is still only about 60-65 degrees. It won't idle in the water at first, you have to start it several times before it will even run with the high idle engaged.

 

[Solittle]

Re: 79 Rude Performance Mystery

Bad t-stats would not account for 2 out of 4 not firing.

 

[BBMerlin5091]

Re: 79 Rude Performance Mystery

ok, in that case i'll get on the timing tomorrow.

 

[gatorboaterUF]

Re: 79 Rude Performance Mystery

ok you have good compression, plugs are firing, assuming you have good timing its gotta be a fuel problem have you soaked the carbs in carb cleaner? that is a must soak em for a few hours and blow em out good then run a small wire trough the idle jets some times air can not clear them out

 

[BBMerlin5091]

Re: 79 Rude Performance Mystery

thanks gator, i'll do that in the morning. i did run into an interesting issue today though. I got a 55 gallon drum, cut it up and filled it with water and put that under the engine, it gave me ALOT of trouble starting with back pressure on the cylinders, but after i did get it to finally idle, i grabbed the primer bulb and squeezed, it was soft, and it sounded like it had alot of air in it. 2 days ago i replaced that primer bulb, the fuel line leading up to the engine, all of the fuel lines on the engine, and all of the clamps on the hoses, nothing is leaking. Anyone have any ideas on this problem, and could this be causing my 2 cylinders not to fire?

 

[fireman57]

Re: 79 Rude Performance Mystery

Your primer bulb will not be hard when your engine is running. I gets hard when you pump it to prime the carb. It will stay expanded when you are running. If it gets sucked flat you have a venting problem. Did the engine have any change when you sqeezed the bulb? Backpressure makes a big difference on how an engine idles. Once you get your cylinders firing properly take the boat out and warm it up good at WOT for five minutes or so then throttle down and set your idle. First things first though let's get them all firing.

 

[BBMerlin5091]

Re: 79 Rude Performance Mystery

ok, sorry took so long, but i finally got around to checking the timing, and it was dead on. to answer your last question fireman, it didn't change a thing when i pumped the primer bulb.

 

[fireman57]

Re: 79 Rude Performance Mystery

Are the same two cylinders not sparking? Can you start this engine in your 55 gallon drum and pull one plug wire at a time to confirm they are not firing? If they aren't then I still would have to suspect a pack. Did you ever get a manual for this engine? You really need an OEM manual. Like DHadley says opposite plugs would point to a carb problem. Have you inspected your fuel pump diaphragm (if it has one) for small tears or waviness. Maybe the hard starting is a sporadic fuel supply from there. Maybe DHadley or Joe Reeves can tell you what might be causing this from under the flywheel if your packs really are good.

 

[BBMerlin5091]

Re: 79 Rude Performance Mystery

The same 2 are still not firing, and yes i started it in my test tank, and pulled the plugs, and they are definitely not firing. I do have a manual for this engine, it's a Clymer. I ran the resistance and output tests on all of the ignition components yesterday, the packs, charge coil, ignition coils, stator.....every one of them was within spec. The only thing left is the fuel system i suppose. I did pull the fuel pump apart right after i got this boat and the diaphram was wavy, do you think that could have something to do with this?

 

[Walker]

Re: 79 Rude Performance Mystery

Tear the carbs down, give them a good soaking in carb cleaner, blow out all the orifices with compressed air, make certain that all orifices and passages are absolutely clean. Then rebuild the carbs with OMC kits.

 

[dolluper]

Re: 79 Rude Performance Mystery

The cylinders that aren't firing change a coil that is firing with one that isn't[have to unhook and reinstall]to make sure, it is possible your sensor coil gap is off or grounding also, your flywheel is torqued right ,pack grounds good or coils ground good

 

[Walker]

Re: 79 Rude Performance Mystery

Well I'm lost here. Do you have spark to all cylinders or not???

 

[BBMerlin5091]

Re: 79 Rude Performance Mystery

There is spark to all cylinders Walker, strong blue spark. When i say that the cylinders aren't "firing", i mean that they have spark but they are not supplying any power to the engine. I can start the engine, let it idle, it misses terribly, but it will run...as it idles i can pull the two plug wires off and they are sparking, but it makes no difference in the idle of the engine so they are not supplying power to the engine. Since i have troubleshot the ignition system thoroughly i have to assume that the problem is fuel related. I'll go and get a couple of carb kits tomorrow and a fuel pump kit and try that.

 

[Basscat 1]

Re: 79 Rude Performance Mystery

I have an 85 hp that had the same symptons. After turning over all stones, it turns out my reeds were not sealing. When you say the engine misses, does it seem to backfire through the carbs, or just run rough?

 

[BBMerlin5091]

Re: 79 Rude Performance Mystery

it runs rough, and it will die repeatedly, but occasionaly it will spit right before it dies, but it's not backfiring. At one point i thought that it might be the reeds, but it seems to me that if it were the reeds, that it wouldn't run good at all. If you can get it to stay running for a minute, you can give it throttle and it will go....turns between 5300 and 5400 rpms at about 60 mph. But if you stop and let it idle for a minute, and then try to get going again it will die and then you have to start all over with it not wanting to idle again.

 

[fireman57]

Re: 79 Rude Performance Mystery

Is your flywheel key sheared?

 

[Basscat 1]

Re: 79 Rude Performance Mystery

If the reeds are not sealing because they are warped or worn it will run rough at an idle, but as your rpms increase you would'nt notice it.<br />My boat done the same thing. It ran great from mid to top end, it just wouldnt idle.<br />Fireman brings up a good point. Check your flywheel key and make sure it is not worn or sheared. It needs a tight snug fit for alignment even though the crankshaft is tappered.

 

[BBMerlin5091]

Re: 79 Rude Performance Mystery

flywheel is good...........well, how do i go about checking the reeds, without totally dissasembling the engine?

 

[reeldutch]

Re: 79 Rude Performance Mystery

you only have to take the carbs,starter and intake manofold off. disconect trotle cable. choke<br />make notes where the resirc lines go.<br /><br />youl see it aint that hard.<br /><br />good luck

 

[Basscat 1]

Re: 79 Rude Performance Mystery

After you remove the reed blocks from the intake, hold them up to the light. If you see any light around the edges, you will need to replace them. Also resurface the reed blocks.<br />I used the Boyesen reeds and I am very well pleased with the performance of my engine now.