The best of today's Diesels

[Maynard Rupp]

OK We might throw in the towel. I have been working for three weeks to overcome the problems with our Crusader 454s. We bought enough diesel, 18%, to dilute our oil etc. I have changed all filters, swapped every bolt on piece etc. Our starbord engine still runs very badly and drops rpm at anything above 2700. Below that it is as smooth as glass. The port runs great. I have deduced that the diluted oil loosened some carbon and the hydraulic lifters are pumping up and holding some of the valves open. Our digital fuel flow indicaters show a large increase of starboard fuel flow when it roughens up. Any ideas?

My son, who is my boat partner thinks it is time to throw in the towel and change to diesels. Maybe the 380 HP Cummins 370 series, or one of the C series. Our '86 36 convertable is as pretty as they come and looks about like new. I guess the investement may be worth it for this boat. We also will have to change the generator. What thoughts do you guys have about the engines or genny. What about Yanmars? Is the new QSB Cummins worth the extra money? My ears are open.

 

[Starman]

Maynard,

Don Charland just bought some Yanmars, at a very good price. He can tell you where that was. 5 year warrenty. He to also looked at the 370 series.

The Yanmars are changing a bit and the new 250hp replaces the 240 hp this year.

Not being an engine person per say, I have heard only good things about the Yanmars.

 

[Genesis]

I'm a Cummins fan myself. If you look at Yanmars make sure you're not getting an engine that has a combined heat exchanger/exhaust manifold. There are dissimilar metals in there and you know what's going to happen to that, right? Its a "service item" - price 'em before you buy. In fact, price ALL parts that that any manufacturer has on the "service" list and also price the parts for a full overhaul. Do it BEFORE you buy the motors, because even if you never need it, a buyer may in the future and he WILL factor that in.

Cummins has a few "brain f@##s" too, but not like that. The weakest thing I know of is the raw water pumps, but there is an afermarket fix for it.

I've been a fan of Kohler gensets for a while. They're using a Yanmar engine that just plain works. I had one in Gigabite and it was an awesome piece of gear with only one problem during my ownership (an injector went bad - cheap to fix)

 

[Trojan]

I looked at a set of Yanmars at the boat show. They sure looked good and the price was real good. I sure would look long and hard at the Yanmars if I needed new engines.
Will your 454 rev up with no load and hold a steady rpm? Does it ever reach high rpm. Does it fall off with no load? That diesel fuel is not doing your engine bearings any good.


BILL

 

[captddis]

Cummins would be my choice as well.

 

[Mike36c]

One more vote for Cummins. I put in a pair of mechanical 330B's in 2004, they run great. You would probably need more HP for the series II 36, I'm thinking QSB-425 would be a nice combination or maybe some reman "C" series 450's to keep the price down if needed. I too looked at the Yanmars before going with Cummins but all the mechanics I talked to said when they run, they run perfect but when they fail, look out. Maybe things have changed but they all complained about part price/availability. The only weak points on the "B" series is the sherwood raw water pump (as Karl mentioned but improved aftermarket replacements are available) and the aftercooler. As long as you service the aftercooler yearly, no problem.

 

[luckydave215]

As much as I'm a fan of Cummins, I have to say that a freind of mine owns four charter boats that run out of Lahaina harbor on Maui, three Bertram 31's and a 37' Merrit. He's gradually changed from Cummins to Yanmars in all four, and swears by them. They use so much less fuel they pay for themselves in one year.
Of course, his boats do two 4 hour charters every day, including about 3 hours daily WOT running, so they certainly get the piss run out of them. Fuel burn might not matter as much to you.
Cummins has good parts support in the islands, so he must have a good reason to favor Yanmars.
Your milage may vary.

 

[Don Charland]

Hieght was a big issue for me. My displacement is about 15,500. The Yanmar 240s are a proven fit for me. Horse power per dollar would suggest the Cummins 370B. Same approx price as the yanmars, 130 more hp. Two inches taller, you will also need to go 1-3/4" shaft and probably larger dia props.What do you have now? You will also have more down angle and ratio options with gears.

 

[34Hatt]

I say CUMMINS

The new ones are sweet but you can save some $ with the reman's which are new motors its a epa thing! But reman's can go into your year. The 370B will make you boat cruise in the lower 20 kt range. 355hp each with 700 lbs of torque.

 

[Avenger]

Add one more vote for Cummins, either B or C. The C series would be the better engine, it's got more cu. in. to work with, and it's a sleeved block. However I think you'd have clearance issues, as well as needing larger running gear.

I'm just curious as to how all the cheering for gas engines went south so fast.

 

[egaito]

Another Cummins Guy here Maynard. I've got C's in Misty, my 41C.

They're rated at 320hp, and push her to about 28 kts and comfortably cruise her at 22-26. Mine are what I'd call "early C's" and they have some kinks, that seem to have been worked out over time.

You might be able to get away with B's in a '36, but pay attention as others have mentioned to the hp/cid. You might even consider some of the "commercial" rated engines rather than "recreational" rated outputs if you're primary interest is reliability.

Also, not too long ago, there was a supply of "reman" C's that were basically new motors at a great price. Not sure if they're still around, but factory reman B's OR C's might be a great way to repower without opening the checkbook quite as wide.

Welcome to the dark side ;-)

 

[REBrueckner]

Don't know this histroy here, nor how many hours your gas engines have nor exactly what's been done, but if the engine runs good except at higher RPM it sounds like it would be worthwhile fixing.

I'm no gas engine guru but I would not think open valves would increase fuel usage.

Sounds like maybe a fuel restriction to me...
Does it run higher RPM ok in neutral but gets rough under load?? even a kinked fuel line could be the culprit..or a dirty carb.

 

[Maynard Rupp]

I looked at a set of Yanmars at the boat show. They sure looked good and the price was real good. I sure would look long and hard at the Yanmars if I needed new engines.
Will your 454 rev up with no load and hold a steady rpm? Does it ever reach high rpm. Does it fall off with no load? That diesel fuel is not doing your engine bearings any good.


BILL

I changed all oil and fuel filters right away. Pumped the tank, blew the lines, changed the fuel pumps and spark plugs. Compression checked . All 16 at 140 to 150. Swapped carbs, ignitions, and coils. Stb. engine starts and runs great until power is up at 2500 rpm or more. OK for awhile, then you can watch the digital fuel flow almost double and engine looses rpm. If left alone it will shut down. Reduce to about 2000 rpm and it is smooth as glass, but fuel flow is still high. 5gph port, 8.6gph stb. I then shut the stb. down for a few minutes and re-start. set both at 2000 rpm and fuel flows are both together and stay that way until you bring the rpm up to re-start the problem. I think the diluted diesel broke some carbon loose and plugged up the hydraulic lifters. Could they then hold some valves open?

 

[Maynard Rupp]

I will solve those 454 problems, but We think we may still re-power. Some of you are mentionink engines with 320 hp. i can't believe that we don't need more. Our torqueless 454s still do make 350 hp and the boat weighs 26000lbs. Jim rosenthall will tell you it is a much bigger than his earlier 36C. Way different boat. We were thinking 375 to 385 hp. would be needed. Are we wrong and why. Our 454s top,(when they are running right), at 24 to 26 knots but struggle to cruise at 17. That is that torque thing eh? I am told that we don't have enough room or shaft size etc. for Cummins "C" series. I also hear that it is hard to find trannys that don't have too much down angle. Our shafts are only down about 3 to 5 degrees. The Crusaders have no down angle drives and are nearly flat. Our stock exhausts are 5", and the shafts are 1 3/4". I don't want to alter them. Our props seem very close also. They are 26" dia. and 23" pitch 3 blabe with no cup.

We are hearing lots of very good things about Yanmars. I think they make a 380hp. or so. I do hear Karl's comments and dissimilar metals is sure a concern. I have a Yanmar in my sailboat and they sure don't give their parts away. I guess they are quieter and smoother than Commins "B" series and they burn less fuel. Is all that true?

 

[luckydave215]

If there are any valves sticking open you'll hear spitting thru the intake or VERY loud ragged firing through the exaust as peak combustion pressures will be venting through partially open exaust valves. If the valves aren't opening due to collapsing lifters, I would expect you'd hear clattering valves/lifters.

My guess is you have a (too high) fuel pressure problem, or the float valve is fooey, forcing the float chamber to overflow, and drowning that engine at high load/rpm. Check your fuel pressure and look down the carb for fuel pouring out of the jets when the engine mis behaves.
It may be as simple as a main jet having fallen out of place. You say the engine revs up normally without load, but at that time the throttle is only open a little bit, not wide open (secondaries) like it is under load.

 

[yachtsmanbill]

Maynard-- I know you changed the carbs, but if they are Rochesters there is something stupid to check that is usually overlooked. Flip the spare upside down and take off the bottom base plate. Six (?) phillips head screws. Under it you will find two small freeze plugs. These are from when the factory drilled the main jet passages. THEY LEAK. This was a GM recall a long time ago. Recommended fix is some gas compatible epoxy mashed in on top of the plugs. Just make sure its not higher than the base.
On another note, my gas boat with a repower from 283s to 454s never would turn up past 3000 without stalling. Pumps, pipes, checkvalves, siphon breaks, filters, strainers, CARBS, tanks, valves, you name it. Even distributors.Even ran new electric fuel pumps. I even stroked the pump cam with a dial indicator--all good. This went on for 3 years. I finally put a vacuum gauge on the BRAIDED flexible fuel hose to the pump and found it not holding vacuum. Just enough to run. Period. They were both 1963 Chris Craft parts made from corrugated copper, covered in copper braid with 1/4" pipe fittings silver soldered on the ends. A crack developed in one of the ribs and ONLY leaked vacuum; never fuel. THAT is whats making your flow meters go nuts!
Two new lines and they spun up to 4600 WOT and proved I had a cracked shaft on the prop taper
BOAT U S was good enough to buy me 2 new shafts and a pair of Dynaquads. FWIW ws

 

[Maynard Rupp]

If there are any valves sticking open you'll hear spitting thru the intake or VERY loud ragged firing through the exaust as peak combustion pressures will be venting through partially open exaust valves. If the valves aren't opening due to collapsing lifters, I would expect you'd hear clattering valves/lifters.

My guess is you have a (too high) fuel pressure problem, or the float valve is fooey, forcing the float chamber to overflow, and drowning that engine at high load/rpm. Check your fuel pressure and look down the carb for fuel pouring out of the jets when the engine mis behaves.
It may be as simple as a main jet having fallen out of place. You say the engine revs up normally without load, but at that time the throttle is only open a little bit, not wide open (secondaries) like it is under load.

Dave, I swapped the csrburaters port for starboard during my troubleshooting and they are still like that with the same results. I have had both an old, and a new fuel pump on that engine. I do smell raw gas in the exhaust and it will pop in the carb if you don't back off the throttle. Can't the lifters pump up to far and hold some valves open? What if I have some stray carbon junk inthe lifters plugging upa hole or something?

 

[Maynard Rupp]

Maynard-- I know you changed the carbs, but if they are Rochesters there is something stupid to check that is usually overlooked. Flip the spare upside down and take off the bottom base plate. Six (?) phillips head screws. Under it you will find two small freeze plugs. These are from when the factory drilled the main jet passages. THEY LEAK. This was a GM recall a long time ago. Recommended fix is some gas compatible epoxy mashed in on top of the plugs. Just make sure its not higher than the base.
On another note, my gas boat with a repower from 283s to 454s never would turn up past 3000 without stalling. Pumps, pipes, checkvalves, siphon breaks, filters, strainers, CARBS, tanks, valves, you name it. Even distributors.Even ran new electric fuel pumps. I even stroked the pump cam with a dial indicator--all good. This went on for 3 years. I finally put a vacuum gauge on the BRAIDED flexible fuel hose to the pump and found it not holding vacuum. Just enough to run. Period. They were both 1963 Chris Craft parts made from corrugated copper, covered in copper braid with 1/4" pipe fittings silver soldered on the ends. A crack developed in one of the ribs and ONLY leaked vacuum; never fuel. THAT is whats making your flow meters go nuts!
Two new lines and they spun up to 4600 WOT and proved I had a cracked shaft on the prop taper
BOAT U S was good enough to buy me 2 new shafts and a pair of Dynaquads. FWIW ws

I know about that plug, but either carb works great on the port engine. I replaced all steel lines and all hoses to the tank when i replaced the pump. Don't forget folks, this thing ran great before the diesel fuel. All of my changes have been in the past 2 weeks. Yes I have worked alot.

 

[jim rosenthal]

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.

 

[luckydave215]

Can't the lifters pump up to far and hold some valves open? What if I have some stray carbon junk inthe lifters plugging upa hole or something?

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.