Need some help with a 302 problem

[blueskyracer]

Two weeks ago our boat ran perfectly..This weekend the motor would run fine on the cart but the minute we sent the boat out and it was under a load it acted like it would suddenly run only on one cylinder..Would not get on plane and it was that way for all three heats on Saturday.. This is our C mod motor and we checked and it has spark at both plugs but the bottom plug was definately wetter than the upper plug.. Put the boat away for Sunday

I have been told to check the kill switch diode since it is a two wire system.. Any more ideas..It definately seems to be an ignition problem..

[bill van steenwyk]

simplest and easiest thing to do.........

if you haven't already is change plugs and see if it solves the problem. If no joy, see if you can get hold of an automotive spark tester if you are convinced it is ignition. Usually Western Auto, Autozone, etc. have them. It is a device that allows the gap the spark is jumping to be lengthened so as to increase the load on the ignition system.

I would agree that from your post it could be ignition, and both coils, spark leads, and plugs can break down under load, but show fire when just pulling over under no load. Also check to make sure the contact between the "sparky" and the plug is good. Since you normally cannot see those sometimes you can have a problem there also.

Lots of ignitions will fire both cylinders under no or small load, but when you load the motor it will break down, and it is sometimes hard to tell by exhaust noise alone.


ADD:

Also check compression on both cylinders. If compression is low on the wet cylinder you could have an internal water leak caused by a blown head gasket on that cylinder. Another tip off is water in cylinder or on the plug.

[doc 35-0]

you still have IT

Bill, good advice Still

[bill boyes]

I had the same problem with a NKG Spark plug boot.
Blown head casket and another possible problem.
I have a 102 that would do that sometimes. Goller told me to check the cyl sleeves. They should be about .002-.003 high. Had a corner was even with the block. Drove me nuts as it would not do it all the time.

[Jack Stotts]

Several years ago a friend had similar symptons for an extended time. Discovered a small piece of cloth in the pipe that had been used to plug it while in storage. Somehow it had been ingested into the pipe. Jack

[blueskyracer]

I may try the easiest solution..New plugs since the ones in the motor are two years old and have about 12 race weekends on them and I will check the pipe for dead things in it

[JWarren]

Plug is possible, testing a plug? just feel the plugs after you run the motor under load as soon as you turn motor off for tempetures. The plugs thats the coldest could be bad or it could be a nother problem. Do you have a fuel pump that runs off the cylinders perhaps? Omc and many other after market pumps will directly bolt to the 302, a blown fuel pump diaphram with cause this issue as well as the cylinder sucks in and blows pressure to over load fuel to a cylinder. I have seen this overlooked many times in the past 25 years of being a boat mechanic. Let us all know what you find would be good food for thought if the problem happens to us. Good luck Jimmy W.

[mercguy]

also......after plugs are replaced........

try a different mag.........the transistor units do fail in the 302 mags (which cause weak or no spark).............I have had 2 fail in the last 4yrs.................

[blueskyracer]

try a different mag.........the transistor units do fail in the 302 mags.............I have had 2 fail in the last 4yrs.................

Thanks Daren.. I guess I will order one to try..Want to try it at Perrygin and hope it is fixed for next year.. We are running a stock fuel system for general info..

Daren are you coming to Winthrop..I am real sure that there will be another D stock there with a Tohatsu and possible two D mods

[mercguy]

Thanks Daren.. I guess I will order one to try..Want to try it at Perrygin and hope it is fixed for next year.. We are running a stock fuel system for general info..

Daren are you coming to Winthrop..I am real sure that there will be another D stock there with a Tohatsu and possible two D mods

it can be cheaper to buy a complete mag, versus a new transistor unit.............not sure about Perrygin............Yelm is the priority and am about burnt out racing this year......

[blueskyracer]

it can be cheaper to buy a complete mag, versus a new transistor unit.............not sure about Perrygin............Yelm is the priority and am about burnt out racing this year......

Then just come for the pot luck..It was sure good last year

[HydroKyle93R]

Try unplugging the kill switch to get on-plane. If you plane off at full power, you know its the switch or the mag.

[blueskyracer]

Try unplugging the kill switch to get on-plane. If you plane off at full power, you know its the switch or the mag.

Well we can give her a try at Pearrygin in about three weeks.. You will be there right??

[Racerkyle20]

Seals

Check them all. Exhust, tower, and head. Not very many bolts or invasive to the motor just to check.

[krazy karl]

I just had the exact same thing happen at Chowchilla. Sent the mag to Ricky but haven't heard back. In the meantime took the motor to Minden and ran it with a good borrowed mag. Had the same issues. Put in new plugs and off it went like a scalded cat.
kk