Trouble shooting low WOT RPM - timing on the 5.0OSi

[lonewolf41]

Still trying to troubleshoot my issue. This is a 5.0OSi-C (maybe a D...it was built in 8/2003). Took my Diacom data to a local Volvo mechanic to get some feedback and suggestions. FIrst of all, he asked if the ECM was in break-in mode. He said the ECM will limit the RPM to ~4400 RPM during the first 50 hours of engine life. This engine was rebuilt. I can't imagine that they set the ECM to break in mode, but maybe they did. I only have 33 hours on the new motor so could that be limiting my RPM? I have never heard of this mode nor do I see it listed in the manual anywhere.

He also said to check timing and set the base timing. I thought timing was all done by the ECM on this motor. From what I can tell, as long as the CAM retard angle is 45 +/- 2 degrees, it is set right. I am pasting a screenshot of my data showing cam retard, engine speed and throttle position. It looks like the cam retard is withing the range it should be ...unless I am reading it wrong. The one thing I am not 100% sure of is if it matters what RPM you set it at. I have seen 1000 RPM and idle. Wasn't sure if it mattered.

Another mechanic told me to unplug the temperature sensors on the exhaust manifolds before starting the motor as that will disable them in case the temperature sensors were bad and possibly limiting RPM. That seems easy enough...although I thought they would cause it to go into limp mode, not just restrict RPM, if they saw high temps.

TIA for any insight or feedback regarding this.

 

[QBhoy]

What is the issue you are trying to diagnose ? Sorry if I’ve missed it in the above. Is it that it won’t go above 4400 rpm ? Did it used to ? And now it doesn’t ? Couldn’t be as simple as being over propped ? Failing that, it may be in one of the many 90% gaurdian modes. Most common cause would be water pressure sensor

 

[lonewolf41]

The start of this can be read here: https://forums.iboats.com/threads/5-0-osi-e-low-power-unable-to-hit-rpm-wot.725345/ still trying to figure it out.

 

[QBhoy]

The start of this can be read here: https://forums.iboats.com/threads/5-0-osi-e-low-power-unable-to-hit-rpm-wot.725345/ still trying to figure it out.

Ok. I remember this one. I’m almost sure that the osi is an mpi type engine ? What are those spark plugs you have pictured in the other post ? Unless the osi isn’t the Mpi I think it is…pretty sure you should have iridium plugs in there ideally. Or at least platinum. They look like very normal plugs. Wonder why they are in it ?

 

[Nashville]

The start of this can be read here: https://forums.iboats.com/threads/5-0-osi-e-low-power-unable-to-hit-rpm-wot.725345/ still trying to figure it out.

A few questions:

(q) Did you have the repower completed, or was the boat purchased used this way? Who did the repower; same with rebuild? Trying to understand history.

(q) Please post picture of the ECM so we can verify what’s installed. Is the 4.3 or 5.0 ECM installed? Unsure after reading history, looking to verify.

(q) The replacement engine was originally matted with a 1.96 ratio, XDP duo prop. What is the drive serial number currently installed, and what exact prop (manufacturer, material and part number… per prior posts, 1:66 and 14 x 19)?

(q) When I look at the data file attached to the current post, max RPM achieved is nearly 4,700. Are we troubleshooting RPM or top speed?

Neither ECM possibilities have a break-in mode/limit that I’m aware of, and if they did, I bet only a VP dealer could “reset” with Vodia as this would would likely be considered a way to drive authorized dealer traffic and proprietary.

 

[lonewolf41]

Ok. I remember this one. I’m almost sure that the osi is an mpi type engine ? What are those spark plugs you have pictured in the other post ? Unless the osi isn’t the Mpi I think it is…pretty sure you should have iridium plugs in there ideally. Or at least platinum. They look like very normal plugs. Wonder why they are in it ?

The plugs shown in the picture were NGK I think. They were the recommended ones from the manual. I wasn't 100% confident in them so I replaced them again this year with AC Delco 41-101 iridiums. No change. And, yes the motor is MPI. Same as the 5.0Gxi motor. Thanks.

 

[lonewolf41]

A few questions:

(q) Did you have the repower completed, or was the boat purchased used this way? Who did the repower; same with rebuild? Trying to understand history.

The boat was not running when I bought it. It had the 4.3L V6 in it when I got it. IT was trashed from salt water. I found this larger motor already rebuilt for about what it would cost me to repair and rebuild the old motor...plus I get some additional horsepower. The rebuild was done by a "certified mechanic", but they did a poor job in general. Left out the gaskets between exhaust and riser, hooked up raw water pump incorrectly, stuff like that. I purchased it already rebuilt. I installed the motor myself.

(q) Please post picture of the ECM so we can verify what’s installed. Is the 4.3 or 5.0 ECM installed? Unsure after reading history, looking to verify.

Pictures are attached, but the ECM came with the motor. I did not reuse the old ECM.

(q) The replacement engine was originally matted with a 1.96 ratio, XDP duo prop. What is the drive serial number currently installed, and what exact prop (manufacturer, material and part number… per prior posts, 1:66 and 14 x 19)?

The drive is the one original to the boat. I did not replace it. It is a 1.66 SX. I have tried the original AL 14x19 and now a stainless 14x21. According to Regal, when this boat came with the 5.0, they changed the drive to the 1.60. They told me I would most likely need to increase the prop size to allow for the difference in gear ratio and the larger motor to keep from over revving it. I can't even get it to max RPM, much less over rev.

(q) When I look at the data file attached to the current post, max RPM achieved is nearly 4,700. Are we troubleshooting RPM or top speed?

RPM. I am not looking at top speed. Just trying to be sure the motor is running correctly in the correct RPM range. I generally run about 3500-4000. I am not a speed demon and it is better on the boat and mileage, but if something is wrong, it could be affecting the entire RPM range and I don't like things being wrong.

Neither ECM possibilities have a break-in mode/limit that I’m aware of, and if they did, I bet only a VP dealer could “reset” with Vodia as this would would likely be considered a way to drive authorized dealer traffic and proprietary.

He said it took Volvo software to set or clear. I have just never heard of it. I think he was full of it as most of the stuff he said I really questioned. He thought he knew a lot more than he did...or at least me, but I have been doing this for decades. This first foray into MPI just has me stumped. Thanks for the questions and let me know if I can answer any more that might help.

 

[Nashville]

The boat was not running when I bought it. It had the 4.3L V6 in it when I got it. IT was trashed from salt water. I found this larger motor already rebuilt for about what it would cost me to repair and rebuild the old motor...plus I get some additional horsepower. The rebuild was done by a "certified mechanic", but they did a poor job in general. Left out the gaskets between exhaust and riser, hooked up raw water pump incorrectly, stuff like that. I purchased it already rebuilt. I installed the motor myself.


Pictures are attached, but the ECM came with the motor. I did not reuse the old ECM.

The drive is the one original to the boat. I did not replace it. It is a 1.66 SX. I have tried the original AL 14x19 and now a stainless 14x21. According to Regal, when this boat came with the 5.0, they changed the drive to the 1.60. They told me I would most likely need to increase the prop size to allow for the difference in gear ratio and the larger motor to keep from over revving it. I can't even get it to max RPM, much less over rev.

RPM. I am not looking at top speed. Just trying to be sure the motor is running correctly in the correct RPM range. I generally run about 3500-4000. I am not a speed demon and it is better on the boat and mileage, but if something is wrong, it could be affecting the entire RPM range and I don't like things being wrong.


He said it took Volvo software to set or clear. I have just never heard of it. I think he was full of it as most of the stuff he said I really questioned. He thought he knew a lot more than he did...or at least me, but I have been doing this for decades. This first foray into MPI just has me stumped. Thanks for the questions and let me know if I can answer any more that might help.

Thank you. The operating range for this motor is 4,600 to 5,000 RPM. The data file shows 4,700 RPM, which is in range. What is causing you to suspect there’s an issue?

P.S. By serial number, 5.0OSi-E. Same as -C and -D, just later in the series.

 

[QBhoy]

I’m still confused about what the issue is. Is it that it’s limiting itself to 4600/4700 or that is all it’s achieving. Two very different things

 

[lonewolf41]

Thank you. The operating range for this motor is 4,600 to 5,000 RPM. The data file shows 4,700 RPM, which is in range. What is causing you to suspect there’s an issue?

P.S. By serial number, 5.0OSi-E. Same as -C and -D, just later in the series.

It maxes out at 4400 RPM normally. I think the 4600 was with the 15 MPH wind. So it normally maxes out at 4400 RPM. I can lower the throttle from full to 60% and there is no decrease in boat speed or engine RPM. It just seems sluggish out of the hole and I have never had a boat that you could decrease the throttle by almost half and there would be no change in engine speed. Now this is the first MPI boat I have owned so maybe it is just getting used to this style of motor. Maybe nothing is wrong, like I said maybe I just need to get used to lowering the throttle earlier due to the dead zone at the top or only move it up to 3/4 throttle for max RPM.

 

[lonewolf41]

I’m still confused about what the issue is. Is it that it’s limiting itself to 4600/4700 or that is all it’s achieving. Two very different things

That is all it is achieving. At some point, it has gone to 4990 (according to the ECU). My normal max is 4400-4500. Nothing on the top 40% of the throttle. Maybe that is normal for an MPI motor. This is the first one I have had so it may just be getting used to how this motor performs. Regal said I would probably need to go to a taller prop to keep from over-revving the motor due to keeping the existing gear-train from the V6. Not only am I not over-revving the motor, I can't get it to max out at 5000. Thanks.

 

[Nashville]

It maxes out at 4400 RPM normally. I think the 4600 was with the 15 MPH wind. So it normally maxes out at 4400 RPM. I can lower the throttle from full to 60% and there is no decrease in boat speed or engine RPM. It just seems sluggish out of the hole and I have never had a boat that you could decrease the throttle by almost half and there would be no change in engine speed. Now this is the first MPI boat I have owned so maybe it is just getting used to this style of motor. Maybe nothing is wrong, like I said maybe I just need to get used to lowering the throttle earlier due to the dead zone at the top or only move it up to 3/4 throttle for max RPM.

The data shows maximum > than 4,400 and in the proper range. Not sure about the wind. If anything, less RPM for any given speed if on the stern and more RPM if on the bow. Remember, the objective isn’t the specified maximum but rather to land within the range. The range is set to allow for more/less occupants, more/less fuel, more/less stuff, weather, water conditions, etc. What exact prop is being run, RPMs at and time to achieve 30 MPH? These three specifics are important to know. The original series of posts bounce and lead the reader to conclude different props have the exact same result, which, if correct, is odd. 1.60 and a 14.5 x 19 isn’t a rare combination for fuel FI 5.0 in a 3,000-pound +/- boat. 1.66 isn’t substantially different enough to cause consternation. If 23, < 4,500 seems expected (but singles aren’t my thing, I’m around vastly more stainless duo props - there are others on this site with far more knowledge so perhaps additional feedback will be received). Regarding throttle position, this ECM reacts to relative throttle position changes (rate) above idle and below maximum and adjusts injector pulse width accordingly (fuel delivery). Different than carbureted. Perhaps just getting acclimated, and not the right prop. But, if the throttle really is non-responsive > 60%, that might mean something.

 

[QBhoy]

That is all it is achieving. At some point, it has gone to 4990 (according to the ECU). My normal max is 4400-4500. Nothing on the top 40% of the throttle. Maybe that is normal for an MPI motor. This is the first one I have had so it may just be getting used to how this motor performs. Regal said I would probably need to go to a taller prop to keep from over-revving the motor due to keeping the existing gear-train from the V6. Not only am I not over-revving the motor, I can't get it to max out at 5000. Thanks.

In that case, it’s likely a prop issue. My similar mpi has a rpm range between 4600-5000 and limits at about 5100ish. Things like fuel, load and trim can make the difference of a few hundred rpms.