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rjbergen

Spike in RPMs

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Today I was cruising in our 2006 Sig 330 with VP 5.7 GXi-F engines and DP-SM drives. I was coming up to speed when all of a sudden the RPMs on the port motor spiked to the limiter. I put it in neutral and the engine was idling fine. I started to give it throttle slowly and didn’t notice any odd vibrations. At about 3k RPM, the port motor spiked again. I cut back to idle and proceeded to idle into an anchorage with no issues. After about 20 minutes we decided to head back to dock since there was too much chop. On the way home I was very gentle on the throttles, and ran about 3,500 RPM and touched 4K RPM at one point. No more RPM spikes on the way home. 

Any ideas on what could cause the RPM spike like that? It definitely wasn’t just the tachometer as I heard the revs too. 

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Did you hear the engine run up or just watching the tach? 

Sounds like a blown coupler. 

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JUNK STUFF around the prop. Dive in & check out the prop for stuff or a bent blade.  Get lucky.

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12 hours ago, Phillbo said:

Did you hear the engine run up or just watching the tach? 

Sounds like a blown coupler. 

Heard it. The strange thing is that we motored home without issues. It happened the first time under acceleration and I pulled back to neutral. Idled for a second to check for vibrations. Applied throttle and it happened again when the RPMs were over 3,000. Came back to neutral again. Tried idling on that motor only and had propulsion with no vibration. We idled around an anchorage area for 20 minutes or so and then headed home. I was gentle on the throttles on the way home, but it had no more spikes. 

My first thought was a blown engine coupler, but then I had power on the way home. Can couplers start to go bad and only slip a little?

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Were the drives tilted up enough that at one point in that chop they were out of the water with no load on them causing the temporary spike?  I know it's a little far fetched but you never know. 

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28 minutes ago, Hatem said:

Were the drives tilted up enough that at one point in that chop they were out of the water with no load on them causing the temporary spike?  I know it's a little far fetched but you never know. 

They were only trimmed up about 1/8th of the way. The thought did cross my mind. We were running in a following sea, so it's possible that the prop caught air and cavitated.

I'm not sure how to diagnose further without taking the boat out for a test run and risk needing a tow back to dock or coming in on one engine.

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1 hour ago, rjbergen said:

They were only trimmed up about 1/8th of the way. The thought did cross my mind. We were running in a following sea, so it's possible that the prop caught air and cavitated.

I'm not sure how to diagnose further without taking the boat out for a test run and risk needing a tow back to dock or coming in on one engine.

At this point determining whether this was a fluke or something real is the objective. I doubt it’s the coupler, but it’s not possible to be 100% sure over the internet. Best is to go out and put it though it’s paces with a friend on board, family and harbor master aware, etc. You have two engines, so needing a tow is unlikely. If it repeats and the motor definitely revs. up, we can go from there. If it does rev., try to notice if the boat slows or stays at/increases speed. Thank you.

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1 hour ago, rjbergen said:

They were only trimmed up about 1/8th of the way. The thought did cross my mind. We were running in a following sea, so it's possible that the prop caught air and cavitated.

I bet you that's all that happened.  Usually the first reaction is something mechanical like blown coupler (which is not out of the realm of possibilities, even though the engines look brand new, they have some age on them) but I think that spike would be more frequent.  When was the last time the outdrives were pulled and alignment checked and shaft greased etc.?

1 hour ago, rjbergen said:

I'm not sure how to diagnose further without taking the boat out for a test run and risk needing a tow back to dock or coming in on one engine.

Just do it.  Maybe dont go too far out.  Trim the drive down a little more and if you have to limp back on one engine, not the end of the world.  At least you'll know it's not the props coming out of the water.   Next step would be to check the props make sure they're ok and then the coupler. 

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43 minutes ago, Curt said:

At this point determining whether this was a fluke or something real is the objective. I doubt it’s the coupler, but it’s not possible to be 100% sure over the internet. Best is to go out and put it though it’s paces with a friend on board, family and harbor master aware, etc. You have two engines, so needing a tow is unlikely. If it repeats and the motor definitely revs. up, we can go from there. If it does rev., try to notice if the boat slows or stays at/increases speed. Thank you.

I'm hoping it's not the coupler because that requires pulling the engine. While it was my initial fear, I'm not so sure being that I had power coming home.

26 minutes ago, Hatem said:

I bet you that's all that happened.  Usually the first reaction is something mechanical like blown coupler (which is not out of the realm of possibilities, even though the engines look brand new, they have some age on them) but I think that spike would be more frequent.  When was the last time the outdrives were pulled and alignment checked and shaft greased etc.?

Just do it.  Maybe dont go too far out.  Trim the drive down a little more and if you have to limp back on one engine, not the end of the world.  At least you'll know it's not the props coming out of the water.   Next step would be to check the props make sure they're ok and then the coupler. 

The outdrives were fully serviced in May, about 15 engine hours ago. The drives were pulled, gimbal bearings replaced, new u-joint bellows, new exhaust bellows, new trim senders, checked u-joint, checked alignment, checked transom shield, and fresh gear lube.

Sounds like I need to take it for a test run. I can wait for a calm day and take it just outside the marina entrance and test it.

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59 minutes ago, rjbergen said:

I'm hoping it's not the coupler because that requires pulling the engine. While it was my initial fear, I'm not so sure being that I had power coming home.

If actual RPM’s and no power, that’s not a good sign. Get the boat out when convenient and safe. Put it through its paces, and determine if the motor revs. up and if it does, is the boat’s speed higher, lower or the same. Don’t counteract by pulling the throttle back unless you know or don’t believe the limiter is functioning.

Given the May scope, the drive shaft would have been cleaned, inspected, greased, etc. Its spline mirrors the coupling. Things happen, but 15 hours isn’t much time. Since you’ve got a fair bit of access to the transom and underneath the motor, suggest getting in there to look for grease thrown about, rubber chunks, metal chunks, etc. Heck, a selfiestick and an iPhone or video camera is often helpful.

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12 minutes ago, Curt said:

If actual RPM’s and no power, that’s not a good sign. Get the boat out when convenient and safe. Put it through its paces, and determine if the motor revs. up and if it does, is the boat’s speed higher, lower or the same. Don’t counteract by pulling the throttle back unless you know or don’t believe the limiter is functioning.

Given the May scope, the drive shaft would have been cleaned, inspected, greased, etc. Its spline mirrors the coupling. Things happen, but 15 hours isn’t much time. Since you’ve got a fair bit of access to the transom and underneath the motor, suggest getting in there to look for grease thrown about, rubber chunks, metal chunks, etc. Heck, a selfiestick and an iPhone or video camera is often helpful.

I was just under the swim platform on Fri scrubbing the algae off the drives. There was no grease noticeable. I used a handheld bristle brush and ducked under the swim platform so I could see the drives. I scrubbed the entire drive housing and the props. No grease on the brush or hands. The prop blades were smooth with no noticeable nicks, dings, or cracks.

I can't say whether I lost power when the RPMs spiked. I brought it back to neutral quickly when I heard the engine rev. I did have power for the ride home and speeds were what I expected. I was running ~24 MPH at 3,500 RPM with full down trim (we were taking a beating in the chop). That's about normal. I run 28-30 MPH at just under 4,000 RPM when trimmed properly and waves are cooperating.

I had no issues docking using both motors to pivot for backing in. So I definitely have normal operation at least at idle speeds.

Sounds like I'll have to take it out for a test and hop in and check underneath.

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41 minutes ago, rjbergen said:

I was just under the swim platform on Fri scrubbing the algae off the drives. There was no grease noticeable. I used a handheld bristle brush and ducked under the swim platform so I could see the drives. I scrubbed the entire drive housing and the props. No grease on the brush or hands. The prop blades were smooth with no noticeable nicks, dings, or cracks.

 

Curt was recommending you look behind the motor, not the outdrives. The coupler is in the engine bay and any debris would present it's self behind the engine.... 

 

 

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1 minute ago, Phillbo said:

Curt was recommending you look behind the motor, not the outdrives. The coupler is in the engine bay and any debris would present it's self behind the engine....

Gotcha! I will check that when I'm down at the boat tomorrow.

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22 minutes ago, rjbergen said:

Gotcha! I will check that when I'm down at the boat tomorrow.

That's why I was asking you when they serviced the outdrives and actually removed them and stuck the alignment tool in through the coupler because then they could notice if something was up with it.

Might be worth asking them when you see them if they stuck the alignment tool in and checked if the coupler looked good along with engine alignment. 

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33 minutes ago, Hatem said:

That's why I was asking you when they serviced the outdrives and actually removed them and stuck the alignment tool in through the coupler because then they could notice if something was up with it.

Might be worth asking them when you see them if they stuck the alignment tool in and checked if the coupler looked good along with engine alignment. 

Not sure what you mean by checking if the coupler looker good? I thought the alignment tool was basically a rod you stuck through the gimbal bearing into the coupler and then checked the grease pattern left by the splines upon removal?

The marina service writer says they always check alignment before reinstalling a drive.

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On ‎7‎/‎8‎/‎2019 at 2:20 PM, rjbergen said:

Not sure what you mean by checking if the coupler looker good? I thought the alignment tool was basically a rod you stuck through the gimbal bearing into the coupler and then checked the grease pattern left by the splines upon removal?

The marina service writer says they always check alignment before reinstalling a drive.

Sorry I missed this.  From what I've read and mechanics told me themselves there should be signs of rubber or metal particles around the visible part of the coupler.  Also how do the splines on the drive shaft look? If rounded or not looking like they should be, then it's probably time to change it.  I had a mechanic tell me he could tell right away once he put the allifment tool in.  Just sucks that the whole engine has to come out for that.  Hopeufltly that's not the case.

 

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So I just checked in my bilge. It’s dry and clean, no signs of grease or debris. I can lean on the engines and see the u-joint splines going into the coupler. The exposed splines have grease so I assume the splines mating to the coupler are greased too. There’s not a sign of any grease splatter or chunks of metal or rubber around the coupler. There’s not even a sign of dust like something is rubbing or wearing slowly  

Is my next step a test run at this point?

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9 minutes ago, rjbergen said:

So I just checked in my bilge. It’s dry and clean, no signs of grease or debris. I can lean on the engines and see the u-joint splines going into the coupler. The exposed splines have grease so I assume the splines mating to the coupler are greased too. There’s not a sign of any grease splatter or chunks of metal or rubber around the coupler. There’s not even a sign of dust like something is rubbing or wearing slowly  

Is my next step a test run at this point?

Thank you. Time for a run taking proper precautions of course. Please, if this repeats, without pulling the throttle back, note if speed stays the same, increases or decreases. If you have knowledge or doubt the RPM limiter is functional, ignore the without pulling the throttle back part.

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On ‎7‎/‎8‎/‎2019 at 2:20 PM, rjbergen said:

Not sure what you mean by checking if the coupler looker good?

Another way (which BTW is all over the internet by full-time mechanics) to tell whether your coupler is not only out of alignment, but also on its way out is to check to rear motor mounts and check the bushings.   If they look over-compressed and cracking and a lot of unevenness on them etc., that's also a sign.

Before taking my outdrive off for inspection a few months ago, I took a really good look at not just the transom motor mounts, but at the front mounts as well.  I even made pencil marks on them just in case anything moved ever so slightly that wouldn't be noticed from a picture.  I guess it's a habit from being a builder. We tend to do reference marks a lot to be sure movement is stable and/or within reason when building and shifting big walls on foundations and especially on foundations.  It also reminded me of that hilarious remark that it's ok for the ransom mount bolts to be 5/8th" loose LMFAOOOOOO!!!!  Oh my God and the lack of humility that came along with that was just STAGGERING!!!!!  But I digress.  Sorry a little out of focus but give you the basic idea.

BDvaTFv.jpg

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Tonight I raised the drives and leaned over the swim platform to check the port drive. No damage to either prop and no signs of any line around them. So I took it out for a spin to test her out, plus the Detroit Symphony Orchestra was playing a sci-fi movie music concert at the Edsel and Eleanor Ford House on the lake followed by fireworks. It was a quick mile or so out of the marine to the anchorage to watch and listen. 

Anyways, on the run out I powered up and everything seemed to run like normal. Came up on plane and the lake was calm so pushed to WOT and topped out at 39/40 MPH with 4 people which is my norm. 

At this point I’ll keep an eye on it, but I’m leaning toward a fluke.

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On ‎7‎/‎12‎/‎2019 at 8:34 PM, rjbergen said:

Tonight I raised the drives and leaned over the swim platform to check the port drive. No damage to either prop and no signs of any line around them. So I took it out for a spin to test her out, plus the Detroit Symphony Orchestra was playing a sci-fi movie music concert at the Edsel and Eleanor Ford House on the lake followed by fireworks. It was a quick mile or so out of the marine to the anchorage to watch and listen. 

That must've been a god time.  Is it easy to anchor or does it take a while to catch?  What type are you using, fluke or plow or one of those boxes? 

The Boston Symphony Orchestra plays at the Esplanade...See the source image...on the Charles River on the 4th followed by the fireworks and to get in there and anchor, it's a major operation.  To come in from the harbor into the river to anchor with one of these is not very easy.

7bd8db09fdd6ab8f22adb28310e1a6dd--charle

And you have to get there either a day early or very early that day and the fireworks don't start until 10:30pm so by then you're a blasted wreck!  But this is what you get.

See the source image

 

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2 hours ago, Hatem said:

That must've been a god time.  Is it easy to anchor or does it take a while to catch?  What type are you using, fluke or plow or one of those boxes? 

The Boston Symphony Orchestra plays at the Esplanade...

[Deleted photo]

...on the Charles River on the 4th followed by the fireworks and to get in there and anchor, it's a major operation.  To come in from the harbor into the river to anchor with one of these is not very easy.

[Deleted photo]

And you have to get there either a day early or very early that day and the fireworks don't start until 10:30pm so by then you're a blasted wreck!  But this is what you get.

[Deleted photo]

 

It's pretty easy to anchor our Sig 330. We have a Delta anchor like this. It works great for the mostly sandy/muddy bottom of Lake St. Clair. We also have 30 feet of chain which really helps. I can't recall a time that our anchor hasn't set the first time we dropped it in the year we've had the boat.

It's been rather easy to go to these fireworks shows on the water this year. We've been to 4 of them this year around the 4th of July. There's a lot of people, but we show up around 7 or 8 and hang out waiting for them. Then we stay half an hour or so after the show and let all of the yahoos rush home. Once the lake is clear, we head back to the marina.

 

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