WOT RPM Too Low - major issue? cause?

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Originally Posted by Holdmybeer

Correct. You have the real thing. I didn't think this applied.

Thinking more, have you ever checked your speed with a phone app. Use the app to compare the other 2. If PP and the GPS on your phone match then the gauge is off for speed. If phone and gauge then PP is off.

RPM being off is still confusing if they are the same signal. But PP focuses on maintaining speed and doesnt really care about RPM. Correct?

At these 40+ mph test do you have throttle left or is WOT maxed out?

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Great idea on phone app, will have to compare.
PP can use speed or RPM set points. In fact according to one of their engineers earlier versions needed RPM signal to work even in speed mode. (bought the boat in February and one of the other gremlins was tach not working on either PP or gauge so he was surprised pp would work even in gps/speed mode without the rpm signal…)

No expert - only beginners and since I had no rpm until i fixed it near the end of season I really only used speed setting so far other than to confirm rpm mode worked too.

So - I have noticed that the last stretch of throttle does nothing to add speed. so I hammer down to say ~80 or 85+% of throttle position and it tops out, then I can still move it down another bit but makes no difference. I have no reference point on whether that’s normal or not.

When off i had my son move throttle all the way forward and back while i looked at the linkage by the engine and it appears to move all the way. ie there is movement past the 80+% point i think. i haven’t checked the tps voltage to confirm it gets to ~4.4v or whatever wot should be. also couldn’t find anything about calibrating or adjusting the throttle linkage in the manual but i’ll have to keep looking bc that would be great to confirm throttle and tps are ‘in sync’ and getting to wot.


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Doing all these runs, the engine isn't mis-firing? No obvious mechanical issues?

This all seems to be electrical based on everything you have checked, just wanting to confirm. Could the TPS sensor be degrading over time? The fact the tach didn't work in February could be part of the issues. What did you do to fix that? Loose ground behind your gauge cluster?

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Originally Posted by Holdmybeer

Doing all these runs, the engine isn't mis-firing? No obvious mechanical issues?

This all seems to be electrical based on everything you have checked, just wanting to confirm. Could the TPS sensor be degrading over time? The fact the tach didn't work in February could be part of the issues. What did you do to fix that? Loose ground behind your gauge cluster?

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no obvious mechanical issues i’m aware of.

don’t think there’s a misfire but not sure how to confirm easily without mefi scanner (no cheap options i’m aware of). plan to look at the spark plugs and if that may give me clues.

regarding tach at one point early in season i had a loose ground at ground bus behind dash causing some other intermittent issues but that was fixed. the tach still didnt work though. had a mechanic look and couldn’t figure it out said grey wire had continuity front to back, i tested a new tach still didn’t work (had some voltage but apparently not enough so thought the signal was there when it wasn’t or wasn’t strong enough), neither analog or pp rpm gauge worked (both off same signal). after looking at connections and disconnecting reconnecting the main harness behind the dash and then the 16pin plug at engine iirc, it started working so assuming it was a loose connection.

yeah could be tps or maybe throttle linkage as noted. not 100% sure how to confirm throttle linkage is working as expected. but if it moves all the way and past the ~80% point where throttle moves but doesn’t increase then yeah i should test the tps. is it just one at the engine or also a sensor at the throttle lever?

also a little confused - my 07 is drive by wire hut maybe still has mechanical linkage from throttle to engine. does that mean it does not have electronic throttle control full drive by wire where there would not even be a mechanical linkage just sensor at throttle?…

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Originally Posted by artg

no obvious mechanical issues i’m aware of.

don’t think there’s a misfire but not sure how to confirm easily without mefi scanner (no cheap options i’m aware of). plan to look at the spark plugs and if that may give me clues.

regarding tach at one point early in season i had a loose ground at ground bus behind dash causing some other intermittent issues but that was fixed. the tach still didnt work though. had a mechanic look and couldn’t figure it out said grey wire had continuity front to back, i tested a new tach still didn’t work (had some voltage but apparently not enough so thought the signal was there when it wasn’t or wasn’t strong enough), neither analog or pp rpm gauge worked (both off same signal). after looking at connections and disconnecting reconnecting the main harness behind the dash and then the 16pin plug at engine iirc, it started working so assuming it was a loose connection.

yeah could be tps or maybe throttle linkage as noted. not 100% sure how to confirm throttle linkage is working as expected. but if it moves all the way and past the ~80% point where throttle moves but doesn’t increase then yeah i should test the tps. is it just one at the engine or also a sensor at the throttle lever?

also a little confused - my 07 is drive by wire hut maybe still has mechanical linkage from throttle to engine. does that mean it does not have electronic throttle control full drive by wire where there would not even be a mechanical linkage just sensor at throttle?…

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I wish I could answer your drive by wire questions. I'm not sure how the assault motor is configured. My Raptor is drive by wire but the linkage it for the transmission to engage.

The loose connection makes sense. These boats take some vibrations and hits while on the water. As good as you describe it running I thought you weren't having engine issues.

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Originally Posted by Holdmybeer

I wish I could answer your drive by wire questions. I'm not sure how the assault motor is configured. My Raptor is drive by wire but the linkage it for the transmission to engage.

The loose connection makes sense. These boats take some vibrations and hits while on the water. As good as you describe it running I thought you weren't having engine issues.

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so you have only one linkage for transmission? I have two - i guess one for transmission and on for throttle. both move together when moving the throttle handle. can’t find any service manual specific enough to this year of the engine to explain or be helpful or even have diagram of what’s what. guessing it’s a little bit of a tweener - bw the non efi and then the full drove by wire…?

and for cars, seems like the boat engine tech was way behind auto engine tech? like a 97 tahoe was using the same motor i have in a 2007? wonder if it’s always like that with marinized engines using older motors no longer being used by newest cars and with emissions requirements for boats lagging?…the only haynes manual os for the indmar 5.7 2003 and earlier. there isn’t one available for later years that i can find…


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For demonstration, here are pics of the linkages I have. I looked back at video and it appears that the linkage moved fully from 80%+ forward. so maybe not linkage issuebut still could be throttle position sensor issue or of course ignition or fuel related. Wish I were still closer to check immediately…
https://uploads.tapatalk-cdn.com/202...5b50751170.jpg

https://uploads.tapatalk-cdn.com/202...cbd0e1171a.jpg
https://uploads.tapatalk-cdn.com/202...3e25439093.jpg


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One additional note - I did have an issue (seems common with older boats) with neutral safety swotch where it would sometimes not register neutral even though the lever was in neutral position. The mechanic who looked at it had me jiggle it in and out of neutral if/when that happens, was told on a forum i need to replace the neutral safety switch (have it on order), and i did notice an oddity in the linkage in neutral that there’s slop in the linkage and it was almost like there was more room to manually put it into ‘neutral’ with the linkage even after the throttle was in the neutral position if that makes sense. don’t know if there’s anything related there to this issue. another thing to look at more closely.


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Well this should explain the half baked dbw implementation in 06-07 models. Basically looks like pre 06 indmars had throttle cables, and 06-07 at least moomba still hadn’t fully converted so throttle at helm was still mechanical with a throttle mate component at the engine to convert mechanical to dbw signal. They say in this post it was 07 but my 07 still has the frankenstein instead of being integrated into the throttle lever. and i guess it’s not a gm or indmar thing and is sorta tweener years so none of the documentation for the engine says anything about it (that i can find) and diagrams don’t show it. wonder how easy it would be to convert to full on dbw….

https://forum.moomba.com/showthread....0527#post70527


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