sliping tx?? Prop??

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Apr 17, 2011
3208N and MG 502. Returning home from fishing trip*stopped to check out oyster bed. Upon accel. to continue, some slipage in the drive train on the port engine. Surge at accel. seemed normal, than there was a release than in a few seconds, 2 or 3 surge again than release. It was repeatable and we determined about 1500 rpm all we could do. Checked oil dip stick when we got home. Oil very clear, in fact so clear hard to tell where it was on the dip stick, but it was 3 or 4 inches up the stick, instead of inch or so to full mark. Compared to the other tx. reading to confirm what I was seeing. No discoloration or burnt odor, foam or frothing.

Just acquired the boat so don't know what PO used for oil, or any history of repair, if any, on this unit. We have about 6 hours on the boat with the last hour being at 2400 RPM. It did have newer hyd. hoses to heat exchanger which suggests *some event.

I have the original manual that came with the boat and tx. when boat was new. No pressure gage on the unit since that port is used for heat exchanger connection. Book calls for T is want to use gage.

New props were put on by the yard when we hauled for survey. Could that prop have "thrown or sheared" the key. Maybe key wasn't used??

Coupler appears normal.

As a start will drain the oil and add fresh, appropriate oil as called for by the book, and pay attention to how much is being added.

Book says there is a strainer. Will try to check that, but doubt it is clogged since oil is so clear on the stick.

I guess I could get a diver on scene to check the prop.

Any other suggestions would be appreciated. Thanks

If not done already, suggest you post same on boatdiesel.
hard to imagine anything enough on the screen to cause slippage....but that was my first inclination was to pull them and look.

Doubt prop...would be a thousand to one in my book but either start there and work forward or the other and back...prop check would seem easy enough but costs right off.* Gotta start eliminating some of the easy stuff.
could b the clutchs slipping under a heavey load, i think it is a twin disck tranny on some of them you can* put new cluchts in without taking out the tranny????
When you operate the port shift lever thru the range; forward to reverse, does it feel the same as the stbd side? Is there a definite detent @ neutral? It is possible that the shift lever on the TX*is loose & not staying in place. Could be a loose cable clamp at the shifting arm, or the retaining bolts have worked loose a bit. Happened to me while getting into a crowded face dock; a bit of a heart stopper.

-- Edited by chc on Saturday 31st of December 2011 10:37:46 AM
Thanks for the advice. I have posted on boatdiesel where I am a member. Didn't think about loose clamp at the shifter station. Everything on the tx. seems tight. Will check that. Going to drain oil and also check screen filter. Oil spec. in the old manual calls for CD that will pass TO-2 or C3 specs. All diesel oil today seems to have passed that by with CF designation etc. Do I use diesel oil in the appropriate weight right off the shelf? (No synthetic).

Boatdiesel forum wondered if there was a trolling valve installed. Said sometimes that could cause problems. Did they ever put trolling valves in the tx. for the Californian because it was a slower cruising boat? Certainly not for fishing purposes.

Maybe of interest, in the configuration now, light loaded, cruise at 2400rpm is 17knots and wot is 21 and just making the rated 2800rpm. Will probably have to remove some pitch from the props to ensure not over loading the engines when we get a more normal loading. Trim tabs not working so don't know if best trim for cruise. In fact seems to be a little bit to much nose down. Making contact with the water really far forward.*Getting*tabs to work is another project, after*we sort out the tx.**

Thanks for the advice.

-- Edited by Fighterpilot on Saturday 31st of December 2011 12:53:54 PM
I have seen trolling valves installed on a few sport fishing diesel boats for*fishing with downriggers when they fish deep and slow for Chinook salmon in the PNW, not common though.**They're more*often found in the commercial fishing fleet.

I'm not familiar with your transmissions, but*the symptoms you're describing sound more like slipping clutchs*or a buiild up of tarnish in the valves, ports and passage ways*in the*transmission.**i had that happen once in a while on one of our*gillnet fishing boats.* It would act like it was slidding in and out of gear while under load.* The mechanic*just change*the fluid*and filter and it*cured it.* But still worth having a qualified mechanic check out before using it much more, just on the off chance it is something else like a prop eating up the end of your shaft.* Ouch!!

Hope it's something easy

Larry B

-- Edited by Edelweiss on Saturday 31st of December 2011 01:36:44 PM
Appreciate the advice. I'm going to drain oil and replace to proper level, after I have pulled the mesh strainer and looked at it. Guess I will use regular diesel oil of the appropriate weight, which for me here in Fl. will be 40 weight. If that doesn't fix it than guess go with a diver next to check prop, than try to get mech. out. I have found they are really loaded up here and it is tough to get a house call. Two that we know and had them do previous work are loaded up with BIG jobs and beg off on our job. May have to ease over to a yard to get it checked.
You can have the drain oil analyzed , to see if it is full of clutch plate powder.

Personally I would never run a 3208 at 2800 except for a min as an engine check.

These are NOT industrial rated diesels ( medium truck marinizations).

Even 2400 for long periods (over an hour) would make me nervous.
The 2800rpm was a short time. Operators manual that came with the engine said to run wot for 4 minutes, note the rpm and back down 400 rpm for your cruise setting. Vintage 1983 manual. I needed wot rpm to determine if I needed to adjust the props. I wouldn't even run it 400rpm under if the props weren't right.

As to cruise rpm would hope could run at 2400rpm, if proped correctly, for a couple of hours. Is your concern it will come apart or just shorten life? It will take about two hours at our 16knots to get to the fishing area, than will throttle back and 2hours again to run home. Traded comfort for speed but my understanding was could run 2400 rpm, in fact expert said could probably run 2500rpm for an hour or two.

The Cat. parts books lists both industrial and marine parts, but your understanding is that all the boat engines were marinized truck engines hence a different rating. Probably so, but even that rating permits higher rpm for so many hours in the day. At least the 3208 has a good reputation so maybe I have a chance of keeping things together for a while. My previous boat had the yanmars at 3300rpm rating--and some yanmars are 3700rpm rated--now they would really hum. Thanks for your thoughts.
I wouldn't be afraid to run a 3208 NA* (210hp) or T or TA (in other words up to the 375hp version) at 2400 for several hours a day a few days here and there.* Even at the pins for those hours/rpms.

I wouldn't run anything except the NA version on the pins for 8 hrs a day by 365.* And yes...better be propped right.* I still say they are 10,000hr rebuildables (I know they are not sleeved)*and there's thousands out there that have proven me right.

My cut on most engines built in the last*25 years or so....they either run much harder than we all think or they all fail from a manufacturing flaw that will happen even if the engine is babied.**It will also happen most likely in the firest few hours or the early part of the engines life.

-- Edited by psneeld on Sunday 1st of January 2012 07:52:14 AM
"At least the 3208 has a good reputation so maybe I have a chance of keeping things together for a while."

Their reputation depends on the power setting.

If you can find it the CAT folks usually have a series of power ratings on the web site.

One is for about 5 min to get a heavy bloat boat to start up on the plane.

The last is 24/7 cont. duty operation.

The 3 in between give various service limits for different power settings.

Check if 2400 for how many hours is OK with the guys that built it.

USE YOUR ENGINE , not something modern that is "close".

Most service life today is figured on a gallons consumed concept.

Run 5gph , say 80 or 90 HP and you might get 8000-10,000 hours of service.

Doubble the hourly fuel burn and you will at least cut the engine service time in half.

Operate near the engines max cont out put , is only recomended for industrial engines , not truck transplants.

-- Edited by FF on Monday 2nd of January 2012 07:34:41 AM
Just read CAT spec /ratings sheets* even the high performance allows 1/2 hour at full power out of every 6 hours of operation and 2 at full power*out of 12 for light duty (patrol boat, etc).* Ran my 1986 - 3208s at 2400-2600 cruise all day long and sold the boat with 3650 hours on the engines...Passed survey/oil analysis with flying colors pushing 20,000 pound sport fish at 20 knots.* Engines are still strong with new owner so 26 years of that duty cycle didn't seem to hurt the 320hp 3208T's.* Most of the guys I know that have the 3208's in Blackfins and Bretrams run them the same.* It was the 475hp versions in trawlers going 18 knots that seemed to give them a bad rap in the last few years of production.
<table class="NormalBorder" style="width:100%;" border="0" cellspacing="0" cellpadding="1" align="center" bgcolor="#808080"><tbody><tr><td class="L1100" valign="top" bgcolor="#ffffff">Intermittent Duty - For vessels operating at rated load and rated speed up to 16 percent of the time, or 2 hours out of 12, (up to 50 percent load factor). Typical applications could include but are not limited to vessels such as offshore patrol boats, customs boats, police boats, some fishing boats, fireboats, or harbor tugs. Typical operation ranges from 1000 to 3000 hours per year. </td><td class="L1100" valign="top" nowrap="nowrap" bgcolor="#ffffff">*</td><td class="L1100" valign="top" nowrap="nowrap" bgcolor="#ffffff">*</td><td class="L1100" valign="top" bgcolor="#ffffff">*</td></tr><tr><td class="L1100" valign="top" nowrap="nowrap" bgcolor="#ffffff">E</td><td class="L1100" valign="top" bgcolor="#ffffff">High Performance - For vessels operating at rated load and rated speed up to 8 percent of the time, or one half hour out of 6, (up to 30 percent load factor). Typical applications could include but are not limited to vessels such as pleasure craft, harbor patrol boats, harbor master boats, some fishing or patrol boats. Typical operation ranges from 250 to 1000 hours per year. </td></tr></tbody></table>

-- Edited by psneeld on Monday 2nd of January 2012 08:15:20 AM

-- Edited by psneeld on Monday 2nd of January 2012 08:16:16 AM
Update on the slipping "something". The TX is looking more and more like the problem. Changed the oil to proper oil and weight. St. 40 diesel oil. Pulled the filter--was clean. Attached a pressure gage which gave me some valuable information. Manual calls for 320PSI. On first check out, at the dock, had that pressure until shifted into gear than pressure dropped to 200PSI. After discussion on and local forum the troubleshooting big question was did drop occur in both forward and reverse? Went back to boat and checked again. This time no drop in either forward or reverse. Go figure. Suggestions were some small piece of trash, probably in the selector valve assembly, finally cleared itself. We'll take it out this weekend for the big test. I have sent the oil off for analysis to see how much metal we have from the previous slippage. Hopefully not much. Thanks for your help. I'll let you know how the test goes.
Here is a "caution" about interpreting the oil results.

I took a sample from my BW Velvet Drive a few years ago, after haulout of my initial season with the boat. Tranny seemed fine, but I am a PM nut and would rather fix something off season. Tranny had close to 3500 hours on it.

Anyway I get my analysis back and see 3500+ PPM of iron! Yikes, that's a lot but what doi I know I show results to Bob Smith of ADC, the ford lehman gurus. He says the tranny is not worth rebuilding with that much iron. Says ADC recommend rebuilding once the iron reaches 350 PPM, and I am 10 times that. Here's the price of a new one. (Gulp!).

So I talk to*an oldtimer at Atlantic Gear which is my local BW distributor. He says it's free to look inside so go for it. So (after I buy a manual) I take it apart and voila there's a magnet epoxied to the bottom of the case (that is not shown in the manual I might add).

So what I assume is that I had unknowingly taken the sample from the magnet hence all the iron. None of the experts even suggested that as a possibility.

Bottom line there was a little rust inside the reverse cylinder and my paper clutches were about to disintigrate, so I rebuilt it myself and even replaced the 2 main bearings, even though they were fine. (since I worked as an enigneer for a bearing company at the time I know how to inspect bearings).


Boat transmissions don't make oil. If they did one would have to carry a barrel around to collect it in. So, a slipping transmission that is overfilled now but not 6 running hours before during the pre=purchase survery, has some type of foreign fluid in it. The heat exchanger uses water on one side of the tubes and oil on the other. When it gets a pinhole it starts leaking one into another. Have your transmission heat exchanger tested. Flush the transmission with clean fluid several times and hope there is no permanent damage. If after several flushes the trans is still acting up, then you'll have to troubleshoot further.
2bucks, thanks for the suggestion. When I had the Cat. Mechanic check it while I stood by the controls he indicated oil level 1 inch high in off position and normal in idle. I want to believe I just didn't know what I was seeing. He said one had to turn the dip stick over and look at the other side to to get true level. I have noted that situation on my truck, but never thought about it on the boat. The sea trial will tell us fixed or not, plus I have a pressure gage for reference as well. Oil was so clear very hard to discern the level.
502 manual calls for level to be checked at idle. I have to flip my dipsticks to read them as well. Your levels sound normal; unless mine are messed up as well.
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