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OAF

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Why is it every time I go out on the boat the transome always gets covered in a black residue from the exhausts, I don't tend to cruise above 2000 RPM, crusing revs should be 2400 and flat out is 2800 but I prefer to travel along at between 1800 and 2000 could this be the problem, am I not going fast enough? On every trip I always have it flat out on the return journey for about 5 minutes just to clear the exhausts and turbos out of soot. Any ideas?

Engines have now done 600 hours, caterpillar 450hp no smoke on start up and no visible smoke when running, very little oil usage, they are due for a service, props and shafts are clean (just been done)
 
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OAF said:
Why is it every time I go out on the boat the transome always gets covered in a black residue from the exhausts, I don't tend to cruise above 2000 RPM, crusing revs should be 2400 and flat out is 2800 but I prefer to travel along at between 1800 and 2000 could this be the problem, am I not going fast enough? On every trip I always have it flat out on the return journey for about 5 minutes just to clear the exhausts and turbos out of soot. Any ideas?
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Never see any soot from my engine, it's not an engine that smokes. But, i find it runs better at "proper" cruising RPM. Any less and the engine actually sounds to be working harder and i'm sure it uses more fuel per NM.
 
What boat/engines?

Cruising rpm should not really matter.
Others will know better, but some engines do have a "sooting" tendency.
VP's from the 80's, Mercruiser/BMW from 80's, no doubt others.
I had a friend with a Birchwood 37 with Mercruisers and it was appalling yet I had a Broom 33 (1991) with Mercruisers that were fine.
I think it can be a sign of over fuelling, which can also be a shortage of air. Volvopaul would correct all the above.

Also possibly a sign of fouling underwater. Try backing the throttles off until rpm start to drop?
 
Can't see any smoke when they are flat out, trouble is at between 26 and 30 knots it's difficult say if there is any because of the spray so if there is is negligible.

Paul you are talking bout one engine? Could it be an exacerbated problem with twin engines?
 
miket said:
Cruising rpm should not really matter.
Others will know better, but some engines do have a "sooting" tendency.
VP's from the 80's, Mercruiser/BMW from 80's, no doubt others.
I had a friend with a Birchwood 37 with Mercruisers and it was appalling yet I had a Broom 33 (1991) with Mercruisers that were fine.
I think it can be a sign of over fuelling, which can also be a shortage of air. Volvopaul would correct all the above.

Also possibly a sign of fouling underwater. Try backing the throttles off until rpm start to drop?
Click to expand...

It's a princess 420 with caterpillar 3126, 450 hp at 2800rpm, and it's bum is clean, air filters are the bigger capacity wash out filters that appear to be clean.
 
OAF said:
Can't see any smoke when they are flat out, trouble is at between 26 and 30 knots it's difficult say if there is any because of the spray so if there is is negligible.

Paul you are talking bout one engine? Could it be an exacerbated problem with twin engines?
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Mine is single engine. Wasn't really a comment about the soot, was more an observation that mine works best at full cruising speed, i think most do ?
 
OAF said:
Paul you are talking bout one engine? Could it be an exacerbated problem with twin engines?
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That's a point
But
If you tootle about a lot and the turbos aren't kicking in often
I have noticed with Big Iveco's (friend has two on a 38footer) when he did 5 to 8kts on pleasure trips with customers.
Say 8 half to three quarters of an hour trips per day
She smoked for a bit when we opened Her up
For about 2 miles then cleared but did leave the transom somewhat soiled
 
Kawasaki said:
That's a point
But
If you tootle about a lot and the turbos aren't kicking in often
I have noticed with Big Iveco's (friend has two on a 38footer) when he did 5 to 8kts on pleasure trips with customers.
Say 8 half to three quarters of an hour trips per day
She smoked for a bit when we opened Her up
For about 2 miles then cleared but did leave the transom somewhat soiled
Click to expand...

I find this with most car engines Rich. If someone has been creeping about in them, the first time you open them up many of them fill the road with clouds of black smoke. A good wellying soon sorts them out :D
 
OAF said:
Why is it every time I go out on the boat the transome always gets covered in a black residue from the exhausts, I don't tend to cruise above 2000 RPM, crusing revs should be 2400 and flat out is 2800 but I prefer to travel along at between 1800 and 2000 could this be the problem, am I not going fast enough? On every trip I always have it flat out on the return journey for about 5 minutes just to clear the exhausts and turbos out of soot. Any ideas?

Engines have now done 600 hours, caterpillar 450hp no smoke on start up and no visible smoke when running, very little oil usage, they are due for a service, props and shafts are clean (just been done)
Click to expand...

3126 E Rating, are you 100% SURE you can make a solid 2,800 rpm at WOT.

5 minutes at WOT is barely enough time to stabilise temperatures, give her some tight wire for at least 15 minutes and confirm #'s you are seeing. Do you have exhaust gas temperature gauge EGT??
 
I have never seen a cat engined princess or fair line with a sooty transom, so I'd be looking at wrong pitch props, I'm surprised your boat won't exceed 30'knots with those motors in as the 370hp 63p version is good for 29 with a clean bottom and light load.

The 3126 has had in the past bad exhaust elbows which corrode the turbos, maybe the boost is down which would give soot, also the intercoolers furr up, has the paint burnt off the intercoolers? Take a look on Thames boat sales site, there is a fair line phantom 41 sor sale on there with a classic 3126 cat engine with totally burnt off paint on the intercoolers, not a pretty sight and a dead giveaway there is a blockage through the sea water side as the heat of the air from the turbo is just burning the paint clean off.

The sea water flow from the sw pump is split directionally from the pump and divided, some to the cac and other to the heat exchanger, as the vanes block in the cac the water can still flow but just straight through the heat exchanger, so you get full cooling but don't realise the charge air temp is high as the engine is still being cooled on the water side.

The down side is that there isn't a clean burn in the cylinders as the inlet air temp is high, net result is the exhaust gas is running high, late starter says, do a test if possible, there should be a port to set a probe in the exhaust outlet near the turbo.
 
I suspect my comments were misunderstood, my apologies for not making my reasoning clear.

When I suggested running motor at WOT for a decent amount of time it was not to give motor a clear out, it was to establish some hard data.

Need to establish 100% that engine is actually making rated speed with stabilised temperatures.

As commented by Volvopaul any loss of CAC efficiency will lead to fall off in performance, 3126 is generally a soot free motor if everything is right. Large proportion of vessels in the US have EGT gauge and Cat publish both a boost curve and EGT curve on their data sheets.

Like all properly developed engines 3126 reaches max EGT in the mid rev range typically 645 C, however at rated speed EGT drops to under 640 C. If you take a test run with benifit of pyro and give motor the beans EGT will climb to max then stabilise and fall slightly as boost builds approaching WOT. If EGT continues to rise CAC is not doing its job properly.
 
Thanks guys for your most helpful replies, I knew Paul's would be a bit more in depth one lol I know about the poor exhaust risers that were fitted, not sure if mine are or not, however they are SS ones and if I am right in thinking it was the cast ones that gave the problems, the water inlet pipe does seem to sit right on the top of the riser which could let water back towards the turbo once the engine is initially switched off.

I don't have exhaust temp gauges but I do have over heat exhaust alarms, they have never sounded.

I do know about the inter coolers blocking and the tel tale sign of burnt paint, I am happy to report that neither of mine have burnt paint and still look like brand new:D but I didn't know that the raw water was split to divide between the inter cooler and the heat exchangers.

Where can I get a turbo boost gauge from and any ideas of the pressure they should be running at? Can you they be tested off load or do they need to be on load

The one engine definitely makes 2800 with ease, the other has only achieved 2400,this happened in the boats first year after that engine had a new prop fitted, Caterpillar did tests on both engines and could not find any reason for it to do it, so it was left as it was, it was suspected that the prop was a slightly different pitch to the other one, I do have the original prop so I might fit it next time it's out of the water, but it is the whole of the transom that gets covered in soot so it's both engines that cause it.

mrs oaf just commented that after our first trips out she remembers me saying how pleased I was that the transome stayed clean, with my last boat P35 the transome used to soot up, (TAMD41B from memory) and I never really pushed that along, so am I cruising to slow:confused:
I do think that as others have said, they need a bloody good *******ing:D

PS Paul the boat is pretty much always fully loaded with gear and tanks and now she only makes about 27 knots flat out, when I bought the boat on trial it did make 30 but only just
 
Latestarter1 said:
I suspect my comments were misunderstood, my apologies for not making my reasoning clear.

When I suggested running motor at WOT for a decent amount of time it was not to give motor a clear out, it was to establish some hard data.

Need to establish 100% that engine is actually making rated speed with stabilised temperatures.

As commented by Volvopaul any loss of CAC efficiency will lead to fall off in performance, 3126 is generally a soot free motor if everything is right. Large proportion of vessels in the US have EGT gauge and Cat publish both a boost curve and EGT curve on their data sheets.

Like all properly developed engines 3126 reaches max EGT in the mid rev range typically 645 C, however at rated speed EGT drops to under 640 C. If you take a test run with benifit of pyro and give motor the beans EGT will climb to max then stabilise and fall slightly as boost builds approaching WOT. If EGT continues to rise CAC is not doing its job properly.
Click to expand...

I think it's beyond my technical capabilities to sort this one out by myself, so I need someone to come take a look and test to see if things are working as they should be

PS what does CAC stand for and someone please tel me what the exact terminology is for WOT:confused:
 
OAF said:
I think it's beyond my technical capabilities to sort this one out by myself, so I need someone to come take a look and test to see if things are working as they should be

PS what does CAC stand for and someone please tel me what the exact terminology is for WOT:confused:
Click to expand...

CAC, Charge Air Cooler, is the equivalent of a diesel cars intercooler.

IMO, you need to get Paul on the job.
 
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