Carbon build up

[67hat34c]

Have the intake off of port motor, Crusader model 350-454. Looked down the intake ports in the heads and can see the back side of the valves and there appears to be a fair amount of build up, lets say 1/8" thick or more. I have been running SeaFoam down carbs of both engines in the past couple of years so it has either disolved some of it or none, cant tell as this is the first time looking at it. I suspect starboard engine has more build up than this one. Also would guess piston top and combustion chambers will also have this build up.

Is there anything I can do outside of pulling the heads? Comperssion testing in the past couple of years indicated a healthy top end on both engines.

 

[guyerst]

I've heard some guys swear by Auto-Rx. Another one of those add to the oil and it automagically cleans everything up. There's an oil forum (Bob the Oil Guy or something like that) where a couple took a peek before and after and claimed it did some good. I can't remember the process, but it's more than just add it and forget. Might be worth a try.

Whatever you try, I'd get some good pictures before and again after so you can see (and show us) if there was any improvement.

Steve

 

[REBrueckner]

Do you run these at low RPM for extended periods...insufficient combustion?? How long has this taken to develop? What do the plugs look like...light gray residue...or wet,dark,black and oily???? Are the plugs the correct ones for the engine...depth, and heat rating???

Are you sure the valves are adjusted ok?? .....I guess so, if compression tests are still good....

 

[67hat34c]

No telling how long, suspect way before we ever owned it. We have owned for about 6 years. Engines were installed in december 1988.
Spark plugs have been black since we have owned it. Done everthing possible to correct this. Compression is 160 area on all 16. only a few pounds difference between any of them. Atributed black to oil leaking past valve stem seals. oily black gone after valve stem seal change on starboard engine so now doing port engine.

I dont want to pull heads. Boat is for sale and she runs strong, no smoke and no oil use. Starboard engine runs about 150rpms less and uses more fuel so I suspect the carbon problem is worse in that engine.

Will start MMO in the gas again and keep using either ATF or Seafoam down the carbs and run her as is. I may try to run the seafoam or atf through vacuum fitting on the carb and use a screw type valve in line to adjust the flow that way it will run in slower and do more good while under way instead of just dumping in all at once and most of it going out the tail pipe.

 

[krush]

Just do water injection

 

[REBrueckner]

"Spark plugs have been black since we have owned it."

That's what I suspected. You are getting incomplete combustion....

I'm no engine expert and maybe somebody else will comment but I KNOW what I would do: put in HOTTER plugs. Be cautious because some brands get hotter with a higher number, others with a lower number,

Usually the white ceramic insulator will be a different length for different hotness...is it more/longer ceramic means a hotter burn???.... Anyway, the WORST that can happen is that hotter plugs will burn a bit faster....opening the gap a bit faster...but that won't happen if you bump up a number or two...

Post your sparkplug brand and model number here and see what others use for comparison....

 

[NAN-PO 41]

This is really getting scary. The other day I agreed with Randy and now I even understand what Krush is saying. Many years ago we used to have real problems with carbon build up. It would get so bad the engines would knock. The solution was to slowly pour a cup of water down the carb at a fast idle with engine up to temp. It would literally steam clean the carbon out of the cyls. Worked like a charm.
Fred

 

[67hat34c]

A few people I have talked to mentioned water but did not say how much.

Starboard engine got this treatment by accident. Water line from pump to cooler burst and caused brakish water to be injested. Was running on the pins at the time. P-4500 S-4300. Well S engine ran up to 4500 just before it started to get too wet down there. Next week changed all hoses on both engines.

May try distilled water. However this will do nothing for the stuff on the back side or stem side of the valves. I am guessing the build up will not allow proper fuel air into cylinders. P engine is the one I have partialy apart but it is the one that runs good. S engine runs strong but uses more gas and runs 200 slower. And over the last few years I have ruled out evertying but the build up, Many old posts on this engine problem.

Anyhow I may go ahead and pull the heads tomorrow from the port engine since it is minus the intake already.

 

[MikeP]

Could be bad valve guides/seals, could be poor ring control, could be a poor fuel/air ratio. Guides/seals are a head only issue, rings are, well...rings which means overhaul. Air fuel is a carburation issue. Looking closely at the back of the valve will help narrow it down.

If it is hard carbon, it is more likely a fuel/air issue. If it is heavier and more oily-feeling, it is more likely to be valve guides. Rings would tend to look more oily but less so than bad guides/seals. The buildup on the back of the valves can get amazingly large and look almost like a small black egg around the valve stem where it meets the valve.

 

[67hat34c]

Mike, I think it was oil from valve guide seals. Out of 16 i think only 3 were not split open.

I was there on saturday , Stuck a probe down there and it seems oily and not hard. It was not as much as i thought originaly but it was still there. Decided to button it back up which I did and fired it up and it ran perfect as always. Compression on both engines is very good, only a few pounds between cyl. and all tend to be around 156lbs. She does not burn oil, no smoke. I Will now watch them with the new plugs which are the ones NGK calls for and see what happens. I will keep doing the SeaFoam and Use MMO in the tanks.

We are going to retire from boating due to the lack of funding and ever increasing expenses. I dont want to spend any more on her than I need to. She runs very strong so there is no real reason to pull the motors apart. If I had the extra money to spend and were keeping her then I guess I would do the job just to make the engines more perfect, same as everything else I have done on her in the last 6 years.

 

[stormchaser]

Just do water injection

Exactly! it actually works VERY well, but ya gotta do it right so as not to hydro-lock the engine. I've done it dozens of times on many engines, it really cleans them up ni9ce with no damage if done right. But damn...the exhaust cloud will make you HATED at the marina, I suggest doing it well away from ANYONE. And be ready to had a very sooty boat after.

 

[MikeP]

Well, that sounds like "good" news, valve seals are the easiest thing to deal with if you choose to do so and can be replaced with the heads on the engine.

Sorry to hear you are leaving boating - you've been on this site a long time! But I can understand finance-wise, at the moment we would like to buy a house in San Miguel de Allende, Mexico and not having our 53 would make that workable money-wise for us. Having the boat makes it not...

 

[67hat34c]

Mike, I did the valve stem seals on starboard engine a year or so ago and the port engine in the last 2 weekends.

Will try the distilled water thing next weekend. Will pull out of the marina and get it done. We are the very first slip in front of the marina bar/grill so will not do it there. Also not wise to have exhaust looking that way for a boat that is for sale. Someone who does not understand will think it has serious issues.

I hate to quit boating but have no choice. This boat has been my pride and joy for many years now and have learned a book full of stuff from you guys. They joy started to go away with the cost of fuel and the gouging from marine suppliers and marina fees and insurance etc. Still not decided on a reasonable asking price but will do so in the next week or so. Sale day will not be a happy day for me inspite of economics.