On one of my engines (1967 427, port side), I have noticed what looks to be fuel out the exhaust at very low (idle) speed. I can't tell for sure, but it looks more like fuel than oil to me.  Just a slight boost in RPM and it stops doing it.  Could it be a mixture adjustment on the carburetor providing excess fuel at the low rpms? If it isn't fuel, I guess it could be oil, but we use very little oil over the course of a season in either engine, although occasionally there is some smoke, again noticeable at low rpm. The engine seems to run very well otherwise.  This is the engine that had the plug wires installed to several of the wrong plugs before I got it.  Any ideas would be appreciated. 

Views: 468

Reply to This

Replies to This Discussion

Kevin - my money is on unspent fuel either because of a down cylinder or timing being off.  Happened to me last year and ended-up being both.  I'd check compression and timing and go from there.  Given how you say it runs well otherwise, might just be timing.

Kevin, We had a very similar issue on our 31 with 327Fs.  We would get a slight sheen on the water from one engine at idle at the dock.  Turned out it was a very small leak in the oil cooler for the transmission.  I'm not sure how much pressure is on the oil cooler lines, but it was enough to push oil through a leak in the oil cooler without letting water go back the other way.

Replace the oil cooler, problem solved.  Never really noticed a drop in the oil level.  Very, very little was getting through, but still enough to put a little sheen on the water at idle.

Darin

Could be a few things, starting by making sure everything is in tune is a good start. Usually running rich has a very distinct smell. I had a float sticking on one of my carbs that was dumping fuel into the carb through the vents. Ran fine under power, but would barely run below 1,500rpms. Of coarse this had to happen on a day with stiff cross winds at the dock. If you don't smell "rich fuel" I would investigate to oil or trans fluid.

The trans should run about 60-125psi.

Good suggestions. I don't really smell anything that smells like I would expect "rich fuel" to smell. I think I will start with the timing and investigate from there. The engine really sounds good at all speeds, even at very low idle.

While you're doing that, Kevin, make sure the crab cap is good.  Whenever my 427s start to act funny, that's the first thing I change.  Amazing how many times that's the culprit.  If there's a crack or something and you aren't getting a good spark, I would think that could also cause unspent fuel.

I'm dealing with the same issue. Been going on for awhile now. I do smell some richness of fuel on the port 350 engine. I had a trans cooler go bad and when it does it will look like pepto-bismal in the water. I will pull plugs and do a compression test. look at all the plugs to see which one may not be firing. If all looks good I will get my old carter carb rebuilt. I had the starboard carb done a few years ago. 

Kevin,

Here is my two cents. And that's about what it's worth. Our engines are old and of an inefficient design to begin with. They are only about 30% efficient by design. You are probably seeing unburnt hydro carbons floating on the water. It could be many of the other things listed above, but I would not get too concerned about it until you experience another symptom. If you find water in the oil or rich burning plugs or increased fuel burn, then I would start chasing gremlins. If you don't have any of that, I would consider it that these old girls were designed in the 60's and efficiency was not a design component. Also, if it makes you feel any better, mine does it too.

I guess I will chime is as well, one of my 350's does the same. Runs fine otherwise, I was considering adding a fuel pressure regulator since I have electric fuel pumps. As a side note I did an oil analysis and there was some fuel in the oil as well. 

I have done a little bit of PM since then, the fuel in the oil may not be related to the fuel in the exhaust. Like you I only get this at idle and when starting the engines, doesn't come up once warm. 

Mine does the same and sometimes smokes as well. I have 427s. I had a mechanic down last year who worked on engines for about 40 years. He tweeked it a little before I hauled it. It definitely changed the sound of the one side. I had some kind of milky looking substance for a bit as well that dissipated. But have had the sheen since I brought it home. I don't know if it did it before I owned it. I will be checking the timing this year as now I am backfiring and losing power at 2500 rpms. I know I am down compression from when I had it tested back when I bought the boat in 2014. I thought maybe the backfiring was solved but it did it on the haulout run last fall.

Captain  Doug

You need to get the valve lash set correctly on your 427 engines ASAP  !!!  The backfire issue at 2500

rpm & low compression is a classic symptom of tight  valve lash and will lead to  wiped out cam lobes !!! 

The best way to adjust them is using the cold lash spec per the Chris Craft service manual .  Do not

run your engines until that issue is corrected

Tim  Toth

Huron  /  Ohio

-------------------------
 
Doug Buell said:

Mine does the same and sometimes smokes as well. I have 427s. I had a mechanic down last year who worked on engines for about 40 years. He tweeked it a little before I hauled it. It definitely changed the sound of the one side. I had some kind of milky looking substance for a bit as well that dissipated. But have had the sheen since I brought it home. I don't know if it did it before I owned it. I will be checking the timing this year as now I am backfiring and losing power at 2500 rpms. I know I am down compression from when I had it tested back when I bought the boat in 2014. I thought maybe the backfiring was solved but it did it on the haulout run last fall.

I'm really glad you chimed in, Tim. I always worry when people accept "well, it's old, it's ok." After what I've gone through with mine, I've realized these old girls can be brought around. Amazing how after three years with mine and making sure they get new plugs every year, those new plug wires, an annual valve job, and proper timing brings them right into shape!

Question before I get up on my soap box :-)

Do you have this sheen just with a cold or cool engine, or would you also have it after a nice long run with the engines up to full operating temperature. Your answer affects my answer !

Reply to Discussion

RSS

Club News

Styled In Fiberglass

For your reading pleasure, the latest issue of the Chris-Craft Commander Club's newsletter, Styled In Fiberglass, along with past issues, can you accessed through the link below.

Styled In Fiberglass Issues

________________________________________

The 2018 Chris-Craft Commander Club National Rendezvous is in the books and it was a great time!!

City of Mentor, Ohio

The city of Mentor, Ohio and the Lawnfield Inn & Suites were wonderful hosts.  A special Thanks to Rob Kneen, the local member sponsor, and Char Pike for the hours of hard work put in organizing and coordinating an amazing weekend. 

The Rendezvous Photo Albums can be accessed through the links below, as well as, under Library, Photo Albums.  We will continue to add links to other albums as they become available. Also below, you will find links to a couple articles written for the local newspaper.

Photo Album 1                 Photo Album 2  

Photo Album 3

Articles:

Chris-Craft Commander Club Celebrates Anniversary in Mentor

Chris-Craft Commander connoisseurs congregate at Mentor Lagoons Marina

_________________________________________

 

© 2018   Created by CCCC Webmaster.   Powered by

Badges  |  Report an Issue  |  Terms of Service