First time drive my hatt

[Toolsntoys]

So we left Annapolis yesterday and traveled to Bohemia river to stop for the night. I was surprised how easy the 53my was to handle in tight space at the marina. Today we are traveling through the c&d canal and heading to cape may. Pascal was right when he said 9kts. That seams to be the sweet spot. I am apprehensive to bring it up and higher. I just don't want any issues for the trip to Connecticut. What are the issues with running the 8v71ti at slower speeds for long periods ? Thanks Pete

 

[rsmith]

Soot will coke on the rings and valves. You need to firewall them for 10 minutes or so every couple hours. The smoke you see will be all the crap burning off.

 

[SEVEN]

Don't be affraid, they are meant to be run.

 

[branwyn]

Soot will coke on the rings and valves. You need to firewall them for 10 minutes or so every couple hours. The smoke you see will be all the crap burning off.

I concur. In our 62' (53') CPMY with 8v71TI's we generally cruise at 1,000-1,100 RPM around 7-9 knots all day. We'll run it up to 1,800 RPM for 10-15 minutes periodically to clean things out. Burn a lot less fuel at the lower RPM too.

Cheers,
Ryan

 

[Top Hatt Craig]

Soot will coke on the rings and valves. You need to firewall them for 10 minutes or so every couple hours. The smoke you see will be all the crap burning off.

I find this very interesting and don't dispute it, my '78 DD manual says to avoid extended idling and if extended idling can't be avoided set idle to 800 rpm.Would you (anyone) know where I might find more on DD low/mid rpm cylinder and valve deposits?Regards, Craig

 

[Boatsb]

There's a member here named bobk. He runs his up and down the coast yearly and is very conscientious. He can state by experience that running them up now and then is a good practice.

There's another member here name rsmith. He has put tens of thosands of hours on his boat and suggested to run them up once a day or so to clear the coke.

Another member named Captdis is a detroit expert (professional mechanic) who will also back it up. What more do you need to learn and why do you need to read about it?

 

[saltshaker]

I find this very interesting and don't dispute it, my '78 DD manual says to avoid extended idling and if extended idling can't be avoided set idle to 800 rpm.Would you (anyone) know where I might find more on DD low/mid rpm cylinder and valve deposits?Regards, Craig

Idling is at idle speed and not under load. That is not the same as running under load at 1000-1200 RPMs. SF regularly troll at idle speed for many hours per day and run at speed to and from thier destinations. The problem is when you run them for extended periods, aren't making required temperature and never run them up before shutting down. You may not hit 170 but as long as you are at least in the 150-160 range you'll be fine. Most Detroit powered Hat MYs run at hull speed 98% of the time.

 

[SKYCHENEY]

X2

I have 4300hrs on mine and I run mostly at 12-1300rpm cruise. I run them up at least every few hours to 2150 for at least 10 minutes. It has served me well and I would not suggest running slow without "cleaning them out" as you WILL have problems if you don't. Ask any here with experience with these engines and they will tell you the same.

 

[saltshaker]

I have to point out that you don't drive a boat you pilot it.

 

[Top Hatt Craig]

X2I have 4300hrs on mine and I run mostly at 12-1300rpm cruise. I run them up at least every few hours to 2150 for at least 10 minutes. It has served me well and I would not suggest running slow without "cleaning them out" as you WILL have problems if you don't. Ask any here with experience with these engines and they will tell you the same.

Thanks for your reply, may I ask what problems are found?Regards, Craig

 

[rsmith]

Thanks for your reply, may I ask what problems are found?Regards, Craig

Most of my boats life was running 3-4 hours to the NE canyon fishing grounds at near wot or at wot throttle speeds. Followed by 8-10 hours of 850 rpm trolling in between. Thousands of hours without a hiccup. In the early 90's I moved the boat to Florida we're 6 miles of slow speed manatee area from the inlet with 11 miles to the fishing grounds. By the time we got out the inlet dropped the riggers and setup the cockpit it wasn't worth cranking it up to run offshore. So I just kept 900 rpm the whole way out. After about 10 trips like this we got hit with one of those Florida summer afternoon whiteout squalls. I decided to get out of dodge and head for the barn. When I cranked up the engines the port started pouring out white smoke and wouldn't get over 1200 rpm. After we pulled the head we found one of the exhaust valves had the skirt torched off like it was cut with a blow torch.
When this unburnt crap builds up on areas that are not designed for combustion bad things can happen. When you crank up the engines after a slow run and see the smoke burning off this is what's happening.

 

[Top Hatt Craig]

Idling is at idle speed and not under load. That is not the same as running under load at 1000-1200 RPMs. SF regularly troll at idle speed for many hours per day and run at speed to and from thier destinations. The problem is when you run them for extended periods, aren't making required temperature and never run them up before shutting down. You may not hit 170 but as long as you are at least in the 150-160 range you'll be fine. Most Detroit powered Hat MYs run at hull speed 98% of the time.

Could it be said you guys with the full size boats and low cruise rpm's have a real issue to be concerned about and that smaller boats that cruise at say 1750 rpm don't see these problems? Thanks again, Craig

 

[saltshaker]

Could it be said you guys with the full size boats and low cruise rpm's have a real issue to be concerned about and that smaller boats that cruise at say 1750 rpm don't see these problems? Thanks again, Craig

The size of the boat has nothing to do with it. Running the engines at low load is the problem. I run mine at 1950rpm most of the time. My slow cruise is 1750rpm so I never have an issue of having to run them up and clear them out.

 

[TopHattandTails]

My rated cruise was supposed to be 2150. But the boat preferred running at 1850 all day long (8v71ti's in a 53my). At the end of each cruise, I would wot them for a few minutes. Mostly to make sure the old girls still had it in her, but after a long day of cruising it also was to burn up any deposits that might be starting. She also hit temp within 5 minutes of running at standard cruise. I never really enjoyed running at hull speed, unless I had too. She didn't like std cruise (2150) due to a lot of granite and extra eight in her. She just struggled to climb the head wave and unnecessarily load the engines. 1850 felt like the motors enjoyed that speed and didn't struggle at all. I've always wot at the end of the day on my's, sf's, express's, and dingy's... Just good std practice on diesels. My $0.02!

 

[TROUBLE]

Is 165-175 degrees hot enough to burn off the build up or do they have to get hotter?


Art

 

[Avenger]

It's about temperature in the cylinders, not the coolant. But if you're not even getting the coolant up to temp you're not working them hard enough.