2002 350HP 3126 question

[Strecker25]

Hi all, still working a deal on a boat with 2002 350HP 3126's. They have over 850 hours, and as I understand it by now should have shown if they had "soft" blocks - but based based on posts from @fwebster in years past I believe the only way to verify they are not susceptible is to look at the block for the FAPS stamp.

I have the SNs, CAT has done their pre-purchase survey (including blow-by), and all fluid samples are healthy. The hull survey is scheduled for thursday so I'll be on the boat and can look around for the stamp but is there any way of telling ahead of time using the SN's?

I want to avoid having the surveyor start his thing only for me to get on the boat shortly after and see they're soft blocks.

Correction: The boat is a 2002 but according to CAT Build Date - 09/25/2000, Test Date - 09/29/2000, Ship Date - 10/05/2000

 

[Strecker25]

also, where on the block is the stamp?

 

[carterchapman]

It's my understanding that the soft blocks failed around 100-125 hours. At your hours, it shouldn't be a worry...

 

[fwebster]

The casting number is located on the top milled face of the engine block just below the head. On the port engine, on a v-drive boat, look near the rear of the engine on the inboard side visible just below the head. Also, the presence of the FAPS casting number does not confirm that you have soft blocks, only that the blocks come from the foundry that made the soft block engines. Even Caterpillar cannot trace the soft blocks to a specific batch or to a specific motor without confirmation by in the field testing with blow by and lube oil sampling.

However, you have already eliminated the soft block issue from these engines by doing the blow by test with results within factory tolerance and by the number of hours on the engines. The soft block usually surfaced as a problem with high oil consumption, blue smoke in the exhaust, and excessive blow-by at about 150 hours. Also, if these were FAPS blocks, your oil samples would had shown fuel and excessive soot in the lube oil.

Suggest you move on and do the hull survey..............

 

[Strecker25]

The casting number is located on the top milled face of the engine block just below the head. On the port engine, on a v-drive boat, look near the rear of the engine on the inboard side visible just below the head. Also, the presence of the FAPS casting number does not confirm that you have soft blocks, only that the blocks come from the foundry that made the soft block engines. Even Caterpillar cannot trace the soft blocks to a specific batch or to a specific motor without confirmation by in the field testing with blow by and lube oil sampling.

However, you have already eliminated the soft block issue from these engines by doing the blow by test with results within factory tolerance and by the number of hours on the engines. The soft block usually surfaced as a problem with high oil consumption, blue smoke in the exhaust, and excessive blow-by at about 150 hours. Also, if these were FAPS blocks, your oil samples would had shown fuel and excessive soot in the lube oil.

Suggest you move on and do the hull survey..............

Thank you Frank!

 

[ttmott]

The casting number is located on the top milled face of the engine block just below the head. On the port engine, on a v-drive boat, look near the rear of the engine on the inboard side visible just below the head. Also, the presence of the FAPS casting number does not confirm that you have soft blocks, only that the blocks come from the foundry that made the soft block engines. Even Caterpillar cannot trace the soft blocks to a specific batch or to a specific motor without confirmation by in the field testing with blow by and lube oil sampling.

However, you have already eliminated the soft block issue from these engines by doing the blow by test with results within factory tolerance and by the number of hours on the engines. The soft block usually surfaced as a problem with high oil consumption, blue smoke in the exhaust, and excessive blow-by at about 150 hours. Also, if these were FAPS blocks, your oil samples would had shown fuel and excessive soot in the lube oil.

Suggest you move on and do the hull survey..............

Didn't Cat already account for all of these defects have been corrected?

 

[fwebster]

They replaced all the soft block engines that were reported, but unfortunately, they had no record of which engines were soft block engines.

Their approach was to warrant all the engines that were found thru or about 1/1/2005 and Caterpillar’s position was that if any engines were going to fail, they would have by done so 1/05 and any failure after 1/05 is the result of normal wear and tear and is not the result of the vendor problem, but due to another cause not covered by a Caterpillar warranty.

 

[Strecker25]

They replaced all the soft block engines that were reported, but unfortunately, they had no record of which engines were soft block engines.

Their approach was to warrant all the engines that were found thru or about 1/1/2005 and Caterpillar’s position was that if any engines were going to fail, they would have by done so 1/05 and any failure after 1/05 is the result of normal wear and tear and is not the result of the vendor problem, but due to another cause not covered by a Caterpillar warranty.

grabbed the photos of the stamps today. No FAPS. Engines ran great but only 2700/2750 WOT. Wasn’t a surprise, the owner told us that’s where they were at. 3/4 fuel, 3 pob, half water. I’m going to swap to aetnas before we pull her for the year so I know where they really run and then get the props worked if necessary.

Only time I saw any smoke was just a small black puff under hard acceleration or when the surveyor ran them hard in reverse.

 

[fwebster]

A slight coating of slime or algae can easily cost you 50-100 rpm. Has the bottom been cleaned recently?

Incidentally, my boat's WOT is about 2750 but she is propped for 2 adults, full fuel and full water. I know it and run her accordingly. As the fuel burn off, the engine load lightens up and I'm not overloading the engines.

 

[Strecker25]

We had it

A slight coating of slime or algae can easily cost you 50-100 rpm. Has the bottom been cleaned recently?

Incidentally, my boat's WOT is about 2750 but she is propped for 2 adults, full fuel and full water. I know it and run her accordingly. As the fuel burn off, the engine load lightens up and I'm not overloading the engines.

We had it hauled for the out of water survey and it was pretty clean prior to the sea trial, they did decent power wash of it when it was yanked out.

I'm half (or more) expecting the stock tachs are just off - of course they could be off in the other direction, but until I can put a laser on them or better yet get the aetnas in I'll run it a little lighter on fuel and water to keep the load down.

I've read through the archives than Dom and others posted about the 410DA/350HP 3126 combo and it looks like the best results are from shaving the props down to 22x22's. The boat has 22x23's on it but with a little cup removed.

It was my first run on a diesel boat, what an experience. The power and consistent thrust compared to gas engines in a head sea is unbelievable and the thing just jumps up on plane

 

[fwebster]

The easier way to manage the engine loads is to divide your WOT rpm by 2800 rpm then multiply that result by 2400 rpm. That becomes your new cruise max rpms and it will not overload the engines.

You are less likely to run out of fuel that way!

 

[Strecker25]

The easier way to manage the engine loads is to divide your WOT rpm by 2800 rpm then multiply that result by 2400 rpm. That becomes your new cruise max rpms and it will not overload the engines.

You are less likely to run out of fuel that way!

frank, can you dig into this a little deeper? I was under the impression that if the engines turn under The target loaded WOT, in this case 2800, then you are overloading them at any rpm in the range. Are you saying that adjusting the cruise load to a lower level accounts for the overprop and keeps the load in cats recommended range?

maybe I’m just misunderstanding. Appreciate your insight!

 

[dtfeld]

I added boost and EGT to mine as a way to help keep track of engine load. My WOT is 2700-2750 depending on load. I like to run at 2350, boost is about 20 psi and the stack temps (not true EGT) are about 780-790 F. I’m trying to keep them below 800 F. My understanding these number are very much in line with other 3126 350 hp powered 410s.

Taking some pitch and cup out is on the list, maybe in the spring. It is interesting to watch the EGT. It will rise and fall 20deg just by trimming the boat.

 

[Strecker25]

I added boost and EGT to mine as a way to help keep track of engine load. My WOT is 2700-2750 depending on load. I like to run at 2350, boost is about 20 psi and the stack temps (not true EGT) are about 780-790 F. I’m trying to keep them below 800 F. My understanding these number are very much in line with other 3126 350 hp powered 410s.

Taking some pitch and cup out is on the list, maybe in the spring. It is interesting to watch the EGT. It will rise and fall 20deg just by trimming the boat.

Interesting - what’s your wide open throttle boat speed? The surveyor clocked us around 31mph I believe, I will get his report Monday to confirm. That was with tabs fully retracted and a little chop

 

[fwebster]

My example and the formula was meant to show the relationship between Max rpm and the appropriate normal load at a desired rpm.

So the maximum WOT for your engine is 2800 rpm and your maximum rated cruise rpm's is 2400, then you boat is correctly loaded at 2400/2800 or 85.7% of WOT.

If your WOT is only 2750, then your max cruise speed should not exceed 85.7% of 2750 rpm or 2356 rpm. Having run the 3100series Caterpillar engine for 25 years, I can tell you these engines have a sweet spot at about 2200-2250 rpm. Cockpit noise is very moderate, turbo whine is entirely;y tolerable and efficiency is a lot better........and, the difference between 2400 rpm and 2356 is not material because you will prefer to run the engines at their sweet spot.

Sorry if I confused you .............

frank

 

[Strecker25]

My example and the formula was meant to show the relationship between Max rpm and the appropriate normal load at a desired rpm.

So the maximum WOT for your engine is 2800 rpm and your maximum rated cruise rpm's is 2400, then you boat is correctly loaded at 2400/2800 or 85.7% of WOT.

If your WOT is only 2750, then your max cruise speed should not exceed 85.7% of 2750 rpm or 2356 rpm. Having run the 3100series Caterpillar engine for 25 years, I can tell you these engines have a sweet spot at about 2200-2250 rpm. Cockpit noise is very moderate, turbo whine is entirely;y tolerable and efficiency is a lot better........and, the difference between 2400 rpm and 2356 is not material because you will prefer to run the engines at their sweet spot.

Sorry if I confused you .............

frank

got it, makes sense now. We were very comfortable at that 2250 mark with about 3/4 tabs. Boat seemed very happy, was making good speed (I believe about 24mph) and as you said the engines were incredibly quiet. I’m so used to gasoline engines at 3500 rpm that I couldn’t believe how quiet they were, I could hear the wake...

Thanks Frank, I’m sure I’ll have loads of questions moving from gas to diesel, but we’re very excited.

 

[ttmott]

got it, makes sense now. We were very comfortable at that 2250 mark with about 3/4 tabs. Boat seemed very happy, was making good speed (I believe about 24mph) and as you said the engines were incredibly quiet. I’m so used to gasoline engines at 3500 rpm that I couldn’t believe how quiet they were, I could hear the wake...

Thanks Frank, I’m sure I’ll have loads of questions moving from gas to diesel, but we’re very excited.

You didn't mention if single engine load testing was done. It is an important test in that it provides a comparison of performance and health between the two engines. This test slowly brings one engine at a time up to full throttle in gear and measures the achieved RPM, coolant temperature, crankcase pressure, induction pressure and temperature, fuel pressure, and a couple of other parameters that the surveyor has instrumented. Then do the other engine. The data between the two are compared and if they are essentially the same you can be assured a couple of healthy engines. Only running both engines together can mask issues one may be having.

 

[Strecker25]

You didn't mention if single engine load testing was done. It is an important test in that it provides a comparison of performance and health between the two engines. This test slowly brings one engine at a time up to full throttle in gear and measures the achieved RPM, coolant temperature, crankcase pressure, induction pressure and temperature, fuel pressure, and a couple of other parameters that the surveyor has instrumented. Then do the other engine. The data between the two are compared and if they are essentially the same you can be assured a couple of healthy engines. Only running both engines together can mask issues one may be having.

this test was done but not by the engine surveyor (cat) but rather the hull surveyor. He did full throttle on one engine, then the other, hard over steering tests while underway, heavy reverse acceleration tests with both one and two engines, and recorded all the data. He did not note a discrepancy in any of the tests from one engine to the other.

 

[dtfeld]

This is my poor mans fuel burn table. The fuel burn is predicated on the Published CAT prop demand curve, and observed GPS speed. This is by no means scientific, as these data points came on different days spread over different seasons/temperatures, and I did not account for wind, current or other variables. Some of the data is interpolated. Basically it just confirms that the 2200-2400 rpm range is reasonable. My EGT and boost are very consistent in this range, and I don’t think I’m cooking the engines at this rpm range. I have not added EGT and boost numbers to the chart, but maybe I’ll add that.

My WOT during my sea trial with 5 people 1/2 fuel and 3/4 water were at 2700 and 25-26 kts (29-30 mph). If I load up on fuel and water and people it drops to 2660, lighter loads 2750. Tuning the props was on the list for last winter, but current job environment has postponed all boat projects. I expect to have them tuned this coming winter. I think a 22”x22” is a better prop set up for me. Longevity of the engines is the goal, and a knot of speed for me is not important.

Cruise for me is 2250-2350 rpm running about 19.5 to 21 kts. Boost reads right around 19-20 psi and EGT 790 F.

 

[Strecker25]

This is my poor mans fuel burn table. The fuel burn is predicated on the Published CAT prop demand curve, and observed GPS speed. This is by no means scientific, as these data points came on different days spread over different seasons/temperatures, and I did not account for wind, current or other variables. Some of the data is interpolated. Basically it just confirms that the 2200-2400 rpm range is reasonable. My EGT and boost are very consistent in this range, and I don’t think I’m cooking the engines at this rpm range. I have not added EGT and boost numbers to the chart, but maybe I’ll add that.

View attachment 90883


My WOT during my sea trial with 5 people 1/2 fuel and 3/4 water were at 2700 and 25-26 kts (29-30 mph). If I load up on fuel and water and people it drops to 2660, lighter loads 2750. Tuning the props was on the list for last winter, but current job environment has postponed all boat projects. I expect to have them tuned this coming winter. I think a 22”x22” is a better prop set up for me. Longevity of the engines is the goal, and a knot of speed for me is not important.

Cruise for me is 2250-2350 rpm running about 19.5 to 21 kts. Boost reads right around 19-20 psi and EGT 790 F.

that’s about where this boat is as well. That 2250 mark was very comfortable and the engine noise was minimal. I’m with you on the speed versus longevity, I’m in no hurry go get places and longer Engine life will always win out.