The best of today's Diesels

[exsailor]

My Yanmar experience was in a Erwin 40 sailboat and it was trouble free for me and the next owner. Our last boat had 1996 420 HP Cummins and they were great except for exhaust risers cracking. The newer ones are better also on soot. It seems to me I read somewhere recently that, although the newer Powerboat Yanmars are lighter and perform well, now that they are getting extended hours on them their reputation is slipping. Be good to hear from someone with extended hours on Yanmars.
exsailor

 

[Genesis]

In theory. But I've never seen it, and I've been around the track a couple times...........Remember, I raced professionally for 20 years.
Check your cam timing. Could it have jumped a tooth?
The other thing I'd change (port for starboard) is the complete ignition. Every symptom you describe could be caused by funny ignition behaviour.

Yeah, good point.

Odd stuff like this can easily be caused by funky ignition stuff. Even something as simple as a bad coil can cause this sort of thing at higher RPM....

It would suck to rip out an engine when its just a matter of something dodgy in the ignition!

 

[yachtsmanbill]

Thats a good point too Dave. If he is still using a centrifugal advance and a spring broke, same results! Another stupid one is to shear the drive gear to cam to oil pump pin in the distributor shaft. But, I dont get the fuel deal.
With either intake or exhaust valves open you'd pop out the top or the end. Compression sounds too good for that, with cam timing too. But hell, we used to index the cam a tooth advanced for more top end or retarded one for more bottom end. Starboard engine is opposite rotation and has gears, the port is standard and has a chain.
Another stupid idea, if the oil pressure regulator stuck closed and RPMs dictated more pressure, the lifters could stay over pumped. One in a million on that with a 454 tho...got to monitor the oil pressure at speed for that. I think that much would blow the rear main seal out.
After all has been done, I would pull vacuum at the tank connection and eliminate the whole supply end for leaks. Could also be a cracked pickup in the tank too. My ROAMER had a 1/32 hole at the top of the pickup in the tank for a vacuum break in the event of a fuel line breaking, the tank wont syphon into the bilge. When I had my problems, I even soldered the hole closed and put in SeaRay (gulp) check valves at the tank valves. Its going to be something real simple. Call Henry Ford!! ws

 

[Maynard Rupp]

In theory. But I've never seen it, and I've been around the track a couple times...........Remember, I raced professionally for 20 years.
Check your cam timing. Could it have jumped a tooth?
The other thing I'd change (port for starboard) is the complete ignition. Every symptom you describe could be caused by funny ignition behaviour.

These things do take me back to my fuel dragster days. These engines have prestolite ignitions and yes I swapped the complete assemblies including the coils. This ia he engine with timing gears instead of a chain and gears. It is the one that rotatesopposite of a car. What really baffles me is how perfectly it runs until you go for some higher power. After that, it flows lots of gas at all rpms. athe only cure is to turn it off for a short time, then re-start. It will now run perfectly again until powered up higher.

 

[Maynard Rupp]

In theory. But I've never seen it, and I've been around the track a couple times...........Remember, I raced professionally for 20 years.
Check your cam timing. Could it have jumped a tooth?
The other thing I'd change (port for starboard) is the complete ignition. Every symptom you describe could be caused by funny ignition behaviour.

These things do take me back to my fuel dragster days. These engines have prestolite ignitions, and yes I swapped the complete assemblies including the coils. This is the engine with timing gears instead of a chain and gears. It is the one that rotates opposite of a car. What really baffles me is how perfectly it runs until you go for some higher power. After that, it flows lots of gas at all rpms. athe only cure is to turn it off for a short time, then re-start. It will now run perfectly again until powered up higher.

 

[Maynard Rupp]

Yeah, good point.

Odd stuff like this can easily be caused by funky ignition stuff. Even something as simple as a bad coil can cause this sort of thing at higher RPM....

It would suck to rip out an engine when its just a matter of something dodgy in the ignition!

Actually Karl, the idea of changing to diesels isn't because of our current problem. I swapped the entire prestolite distributers and coils. It runs great until you get it up to higher power settings, runs fine when throttled back except for high indicated fuel flow. Stopping and re-starting cures the fuel flow until you power up higher again. We get a raw exhaust gas smell and it will backfire when running badly. It doesn't run bad at first powerr up either. It runs fine for a few minutes then the fuel flow about doubles and the problem starts.

 

[MikeP]

Hi Maynard,

Well, let's don't over science this thing. It was running perfectly before the diesel got put in the gas tank, right?

If so then it's pretty safe to say that the problem resulted from that. Ok, so now what problems could occur from diesel in gas? The only "system" directly affected is the fuel system.

I don't frankly know if diesel will act as a "cleaner" in a gas system in the manner of say, Marvel Mystery Oil. If it will then it has the potential of continuously clogging fuel filters with the gunk that has been loosened in the fuel system for MONTHS - I've seen that happen with MMO added to gas. So, after you replaced the fuel filters have you ever checked them again? In the situation I referred to, I saw the primary filter clog completely - engine wouldn't run - in 15 minutes.

When you say the engine is smooth below 2700RPM, is that under load or no load? If it will rev to high RPM - 4000+ at no load, then this points even more firmly to a fuel delivery problem. If it won't then it is possible we're dealing with something else.

It is possible for lifters to pump up and float the valves but this occurs at high RPM - much higher than these engines can (should) rev. As far as carbon "clogging" the lifters, I have never heard of that happening but I suppose anything is possible. If the valve lash is properly set with the hydraulics, the most they should be able to do is pump up to remove all the working clearance which still shouldn't float the valves under any normal RPM.

How are gas fuel pump diaphragms affected by diesel? Personally, I don't know but since many oils adversely affect various types of "rubber," there could be a fuel pump problem with a porous diaghragm. Don't count on the clear tube that's supposed to tell you if there's a ruptured diaphragm - check the fuel flow with the fuel line disconnected from the carb while you spin the engine with the starter. You should get a good healthy solid spurt of fuel every cycle.

Float level issues could cause this but since either carb will work fine on the other engine, that pretty much eliminates the carbs (Q-Jets are junk carburetors BUT if they're working, they're working).

I got to this point in writing and then found that you had added another post...

In your latest post you mentioned "What really baffles me is how perfectly it runs until you go for some higher power. After that, it flows lots of gas at all rpms. athe only cure is to turn it off for a short time, then re-start. It will now run perfectly again until powered up higher"

When you say it flows a lot of gas what do you mean? Are you checking the fuel flow somehow?

Again - no load? Does it initiallly rev up to, say, 4000 and then start sputtering and backing itself down to a lower RPM? Will it hold that lower RPM? Or will it just never go above 2700 at all?

We'll sort it out - For God's sake, they're just Chevys - there's darned sure no rocket science involved and no need to fool around with repowers! (unless you just really want to do that, of course)

 

[yachtsmanbill]

Any chance of a flexible hose delaminating on the inside blocking off flow? Instantaneous low fuel cold cause the float to be sucked open or lift the power valve in the carb off its seat and flood. Do you run a choke pull off that may be allowing the choke to close? Put a clothes pin on the butterfly and try it. ws

 

[captddis]

A number of years I had the same problem on a cust 35 Viking with 454 Crusaders. The problem was a loose connection on a terminal on the ballast resistor. A few years ago I had a similar problem as well on a new pair of EFI engines I installed on a Chris Craft. one would run fine to 3200 then die. It was a bad harness on that one. It would set up a harmonic resonance at that speed to shake the wires just right.

 

[captddis]

A bad coil wire will do this also. had it happen a couple times

 

[Mike36c]

Hmmmm, Once the higher RPM problem starts the only way to fix it is to shut down the engine, wait a short while, then re-start? A fuel vacuum issue? Have you tried feeding the engine directly from a portable fuel tank?

 

[egaito]

In theory. But I've never seen it, and I've been around the track a couple times...........Remember, I raced professionally for 20 years.
Check your cam timing. Could it have jumped a tooth?
The other thing I'd change (port for starboard) is the complete ignition. Every symptom you describe could be caused by funny ignition behaviour.

Cam timing...that's an interesting thought. I had an old Buick that did just that. Backfired, then ran exactly as described. Once I replaced the chain (and reset the cam timing), she ran great.

On the ignition side, I've seen this symptom out of Chrysler inboards, with bad ballast resistors. I don't know if Crusaders have an equivalent weak link in the ignition though.

 

[Maynard Rupp]

Thanks everyone..First, all components of the ignition have been switched including coils. I also can't believe that the diesel fuel isn't the culprit. I suppose a primary wire feeding the coil could be bad, and I will check that. The oil was BADLY diluted by the diesel operation. I drained 4 gallons from each engine. This problem started about 1 hour after we got that diesel fuel though. The port engine as always run great. I removed and looked through every rubber line. These were new last spring. The steel lines and fuel pump have been changed since the diesel,(last week). I am sure happy to have the oppurtunity to pick so many good brains. Please keep the thoughts coming. We have been thinking about the diesels for some time. Everyone in Florida looks at you like you are sick when you tell them that you have gas engines. When fueling, you have to get angry before the guy will agree to pump gas into a sportfish.
I can't think of a simpler power package than a pair of good old 454s. You also will never find one that is cheaper to maintain.

 

[egaito]

Maynard, I would suggest you talk to either Tony Athens in California, or Tom Slane, or both. There were diesel options (two evidently) for these boats when new- my guess is 6-71s, 6v53TIs, or Cummins V8s... the only CAT available then would have been the 3208- maybe that was an option as well.

If you have 1.75" shafts you might be able to get up to the "C" series Cummins; if not, you would be limited to the "B" series engines. I think 385hp with 1.75 would be at the outside limit of the 1.5" shaft, and I might be wrong on that.

As you know, it's torque that does the work of turning the wheels, and for a given hp rating, diesels have much more torque available all through the rev range. The hp rating is not as important as how much wheel you can turn. I think appropriate gears will be available- after all, they had diesel options when new and this stuff isn't all out of production.

"Unity" is the best looking Series II 36 I have seen. If any boat is worth repowering, she is. Keep in mind, though, that you will be upside down, probably permanently, when you are done. In terms of economics, I mean.

This will be "heresay" (as apposed to heresy ) but Misty was upgraded to 2" shafts with the repower to C's. I can't say who recommended it (Cummins, Twindisc or yard), but folks that have worked on her all seem to think it made sense. I believe the original struts had enough meat in them, and were bored to accept a larger cutlass bearing. Either that, or they did a great job of repairing the old strut mounting locations inside and out.

I agree also after seeing Unity, that she would be well worth the upgrade!

Noise was mentioned elsewhere in the thread...talking with the Cummins rep at the Miami show, on the topic of B's being in Dodge Trucks, I asked when they were going to make something for the road as quite and mild mannered as a Duramax engine/tranny package (they really drive great and are quiet).

He said the new QSM's, electronically controlled, were about 30% quieter due to similar injection timing techniques. It seems most of the noise from a diesel comes from the pistons rattling in the cylinders due to the force of the explosion. When you "drip" part of the fuel charge in, then introduce the rest, you get a small explosion that in turn lights off the rest of the fuel charge, less violently and therefore more quietly. Someone correct me if I messed up that explanation, but I wonder if the same benefits are being realized in B's or C's yet.

-Ed G.

 

[SKYCHENEY]

Maynard,
You said that you blew all of the fuel lines out after the diesel. Do you think you could have caused any damage to the lines with the pressure. Did you use compressed air? I'm just trying to think of something that has not been discussed yet. Have you tried running from each tank (I assume you have 2 tanks). Could the tank selector valve be the problem? It sure sounds like a fuel issue. If that system was drawing air into it somewhere, could those bubbles be messing up the flowscan and make it think you were dumping fuel in there when really it was actually starved for fuel? Just some thoughts.

 

[dougl33]

The fact that you can smell raw gas in the exhaust leads me to believe its an ignition problem and not fuel restriction. If you weren't getting enough fuel to the engines, I doubt that you'd smell it coming out the exhaust.

Excuse my ignorance as I've had nothing but Mercruisers in my 2 Berts. Do these Crusaders have an electronic ignition? My current 33 Bert had 454's with Merc Thunderbolt Electronic iginition system (prior to re-powering with RTO 6BTA's this winter!). My 28 Bert had 305's that I "upgraded" to the Thunder Bolt electronic ignition. In the 5 years I ran the 454's with the factory installed ThunderBolt iginition I never had one problem.

The 305's in the 28 is another story. Back in 2001 I had my mechanic switch the 305's to the Thunderbolt system in June. I ran the boat most of June and into July (about 20-25 hours) before leaving for a trip to Nantucket. I wasn't a half hour into my trip when the port engine started losing rpms. After a few minutes it would die out completely. After a half hour or so, I could re-start the engine and get another 20-30 minutes out of it before it started all over again. Since it was foggy out anyway, I went all the way to Nantucket mostly on 1 engine (about 110 miles over 2 days). When I got to Nantucket I had a mechanic crawling all over the boat for 3 days switching everything back and forth to try and isolate the problem: coils, carbs, alternator, batteries, cap, rotor, wires, plugs, etc...) Finally nearing the end of the 3rd day he switched the match book size ignition sensor module for the Thunderbolt iginition. Sure enough, after 30 minutes the starboard engine started acting up. So it cost me around $900 to diagnose a problem with a 6 week old $70 sensor.

 

[Avenger]

Okay, I'm going to take a crack at this, but I'll warn you up front that I'm more of a diesel guy. Do you have any kind of sight glass on the fuel system? Is it possible that the fuel supply to that engine is becoming aerated? If the fuel going into the bowl is foamy it may settle out at low loads, but once the demand goes up you're not getting solid fuel and developing a lean miss? Maybe a bad standpipe in the tank or a faulty line. Just a guess.

 

[Capt Ratty]

Maynard
Have you checked the cam? Running on dilutrd oil starves the camshaft of oil and will wear the lobes down. It may run fine at lower rpm, but when you pour the coal to it, it will backfire, spit and cough. Fuel consumption will go way up. Just pull the valve covers, and see if the rockers are moving an equal amount of travel.

 

[Maynard Rupp]

Maynard,
You said that you blew all of the fuel lines out after the diesel. Do you think you could have caused any damage to the lines with the pressure. Did you use compressed air? I'm just trying to think of something that has not been discussed yet. Have you tried running from each tank (I assume you have 2 tanks). Could the tank selector valve be the problem? It sure sounds like a fuel issue. If that system was drawing air into it somewhere, could those bubbles be messing up the flowscan and make it think you were dumping fuel in there when really it was actually starved for fuel? Just some thoughts.

Thanks, Sky...Unity has only one tank. I removed all lines after blowing the diesel/gas mix out with my mouth. (I have been called a blowhard). my compressor is in Detroit. I have discovered that the high indicated fuel flow on that engine is not a true reading. I just gassed this thing today and the total used was 180 gal. The indicated said we needed 233 gal. The difference was totally reflected in the "stb. fuel used" entry. We are using a Navman fuel syatem, Sky, not FloScan. I am going to remove the stb. engine flow sensor and replace it with a tubing piece. Maybe that thing is sending the gas around in a circle or whatever. I did remove and sight through every flexible line and replaced all steel lines. It is running great now for at least 10 minutes at higher power settings. One of the guys on this forum asked what the no load high rpm operation was like. I ran it to 5000 rpm in neutral and left it there for over 1 minute. Smooth as silk and doing that seems to have helped the problem. Shure is a crazy one. I have built many of these engines for race cars. They are simple and fool proof. I have been tearing the few hairs I have out with this one.

 

[Maynard Rupp]

Maynard
Have you checked the cam? Running on dilutrd oil starves the camshaft of oil and will wear the lobes down. It may run fine at lower rpm, but when you pour the coal to it, it will backfire, spit and cough. Fuel consumption will go way up. Just pull the valve covers, and see if the rockers are moving an equal amount of travel.

No. but I sure hope you are wrong. Not impossible though. The oil is nice and clear and my magnet didn't pick anything up in the oil pan.