2010 Tahoe Q5i 4.3l will only make 3500-3700 rpm, 32 mph

[ohaze]

Hello, my 2010 Tahoe Q5i is only making it to 3500-3700 rpm and tops out about 32mph WOT and trimmed with just me in the boat (215lb). 4.3l carburated 190hp with stock 14x23 three blade prop. Tried a new 14x23 four blade (should be a 14x21) but results roughly the same. Prop hub is good (no prop slip). Boat is new to me but from what I have read should be making 4400-4800 rpm and at least 40mph. Any ideas?

 

[KD4UPL]

You need less pitch, not more, to get your WOT RPM up where it needs to be.

 

[Scott Danforth]

Way too much pitch

 

[BCran]

Hello, my 2010 Tahoe Q5i is only making it to 3500-3700 rpm and tops out about 32mph WOT and trimmed with just me in the boat (215lb). 4.3l carburated 190hp with stock 14x23 three blade prop. Tried a new 14x23 four blade (should be a 14x21) but results roughly the same. Prop hub is good (no prop slip). Boat is new to me but from what I have read should be making 4400-4800 rpm and at least 40mph. Any ideas?

I have a 2011 Q5i with 4.3L TKS. This is the fish and ski version. I’m running the original 14x23P 3-blade Aluminum Prop and get 4800 at WOT. Speedo says 55 mph and based on other boats I’ve had, 55 feels pretty close to correct. The calcs say I only have 5% slip with this setup. I’m happy with the overall performance. Good hole shot and top end is adequate.

I have been considering a SS prop since I run on a lake that has a few underwater hazards. My understanding is that if I switch to a SS prop, then I should drop from 23p to 21p. I can’t offer much help with the 4 blade props.

What are you trying to achieve? Better turning, better hole shot? Have you tried the mercruiser prop selector on line?
BC

 

[BCran]

Hello, my 2010 Tahoe Q5i is only making it to 3500-3700 rpm and tops out about 32mph WOT and trimmed with just me in the boat (215lb). 4.3l carburated 190hp with stock 14x23 three blade prop. Tried a new 14x23 four blade (should be a 14x21) but results roughly the same. Prop hub is good (no prop slip). Boat is new to me but from what I have read should be making 4400-4800 rpm and at least 40mph. Any ideas?

Here is the prop number for the 23P I mention below.
832834A45P23 Mercruiser

 

[ohaze]

Thanks for the replies, my primary concerns are that either the engine has an issue by not making power with the factor 14x23 three blade prop or that I may be over loading (tasking) the engine. This evening the water was flat/calm and I tried both the 14x23 three blade (that it came with when i bought it) and then the new four blade 14x23. The three blade ran horrible, switched to the four blade and performance improved to 4,100 rpm a d about 40mph. The three blade would only run 30mph @ 3500rpm. I did not think the three blade had prop hub spin, but now it seems almost certain it does. I'll get a new one and see how that goes. Again thanks for the replies.

 

[Bondo]

Boat is new to me

Ayuh,..... Welcome Aboard,...... If yer not gonna do a full service on it, at least change the fuel filter, 'n dump the contents of the old one into a clear vessel, 'n look for anything but clean fresh gasoline,.....

 

[nola mike]

Thanks for the replies, my primary concerns are that either the engine has an issue by not making power with the factor 14x23 three blade prop or that I may be over loading (tasking) the engine. This evening the water was flat/calm and I tried both the 14x23 three blade (that it came with when i bought it) and then the new four blade 14x23. The three blade ran horrible, switched to the four blade and performance improved to 4,100 rpm a d about 40mph. The three blade would only run 30mph @ 3500rpm. I did not think the three blade had prop hub spin, but now it seems almost certain it does. I'll get a new one and see how that goes. Again thanks for the replies.

Still seems a bit slow for that hull. Either you're still over propped or you have an issue. I'd check compression, at least to get a baseline. Should be getting 4800 rpm with just you on board.

 

[ohaze]

Thanks, I'll definitely be getting a full service on it with compression check. I've run three tank fulls of gas through it. The first had heat added to try and eliminate any potential water/fuel issues but that gas is long gone. I'm at Table Rock Lake (Branson,Mo) for the week on vacation so will be running a lot more gas through it. One other thing now that I think about it is fuel mileage. I'm burning 3/4 tank p/day - which with the distances I'm running seems a bit excessive.

 

[ohaze]

Oh and the four blade, making 4100rpm and 40mph WOT run i meantioned yesterday was with four people, so around 500lbs. Still would think I could get to at least 4400 rpm based on what it seems others have experienced with a q5i 190hp. Holeshot power comes on slow also, but does build fairly well, just not pulling up any skiers for sure. Not that I'm trying to, but seems that could be better also.

 

[QBhoy]

Something isn’t healthy. I’d have a check of the fuel filter, if your numbers are accurate. You should easily be seeing mid 40’s gps on a bad day.

 

[nola mike]

Something isn’t healthy. I’d have a check of the fuel filter, if your numbers are accurate. You should easily be seeing mid 40’s gps on a bad day.

I only got 42 mph/4400 rpm the other day with my new 4 blade/9 aboard. Haven't tried solo yet, but with old 21p and just me I'm getting 47/4900. Mine is allegedly around 220 hp, though I don't think I'm getting that.

 

[QBhoy]

I only got 42 mph/4400 rpm the other day with my new 4 blade/9 aboard. Haven't tried solo yet, but with old 21p and just me I'm getting 47/4900. Mine is allegedly around 220 hp, though I don't think I'm getting that.

Is that the mpi you have Nola ? I’ve propped a few similar boats that size and with the mpi 4.3 now. Found that these things absolutely and essentially require very careful propping, to run at their best. Fairly typical for them to be a little lazy down low, I found. Ideally they need to be propped as close to the limiter (or even on it if light) top end…just to help them out low down. Sounds like you are about that anyway. Further to that…and after lots of messing and experimenting…I couldn’t believe the difference in performance results, between the handful of props within a couple of inches of each other. Happy to tell you all about the exact details, if you’re at all interested, but long story short…the overwhelming top prop that showed best suited, by a huge margin, over the rest…was a 3 blade tempest plus. Won’t bore you with everything, but just one example of what I mean…would be comparing the tempest to a 4 blade ally merc prop (might have been a nemesis…can’t remember right now without the details recorded to hand).
So despite the tempest being a 19”…and the nemesis being a 21” pitch. The 4 blade ran up to the limiter at around 4900-4950 rpm from memory. Doing around 46 mph at its very best I’m sure. The tempest of less pitch…ran an incredible 52 or maybe even a 53 mph gps at just over 4900 im sure. Only touched the limiter for a second and once. When really trying and light. Had enough grip down low to plane well too. Also outstanding and very evident was the huge difference in cruising efficiency when running in the mid 20’s. Vastly more efficient on the smartcraft fuel figures. Actually showed lower rpm than some of the 21” props tried.

 

[nola mike]

Is that the mpi you have Nola ? I’ve propped a few similar boats that size and with the mpi 4.3 now. Found that these things absolutely and essentially require very careful propping, to run at their best. Fairly typical for them to be a little lazy down low, I found. Ideally they need to be propped as close to the limiter (or even on it if light) top end…just to help them out low down. Sounds like you are about that anyway. Further to that…and after lots of messing and experimenting…I couldn’t believe the difference in performance results, between the handful of props within a couple of inches of each other. Happy to tell you all about the exact details, if you’re at all interested, but long story short…the overwhelming top prop that showed best suited, by a huge margin, over the rest…was a 3 blade tempest plus. Won’t bore you with everything, but just one example of what I mean…would be comparing the tempest to a 4 blade ally merc prop (might have been a nemesis…can’t remember right now without the details recorded to hand).
So despite the tempest being a 19”…and the nemesis being a 21” pitch. The 4 blade ran up to the limiter at around 4900-4950 rpm from memory. Doing around 46 mph at its very best I’m sure. The tempest of less pitch…ran an incredible 52 or maybe even a 53 mph gps at just over 4900 im sure. Only touched the limiter for a second and once. When really trying and light. Had enough grip down low to plane well too. Also outstanding and very evident was the huge difference in cruising efficiency when running in the mid 20’s. Vastly more efficient on the smartcraft fuel figures. Actually showed lower rpm than some of the 21” props tried.

No, I have a chevy blazer 4.3 vortec with a 4 bbl edelbrock. New prop is a turning point hustler. Hoping that I can get a bit more stern lift and bite. The 3 blade starts to break loose at 4900, I feel like I should be able to trim it more. I want low end skiing grunt, don't care too much about top speed. Should be getting my O2 exhaust spacer today, and have a wideband O2 sensor/AF gauge ready to install to see if I can tune the carb a bit better. Wish I had access to a prop shop and a bunch of props to try...

 

[QBhoy]

No, I have a chevy blazer 4.3 vortec with a 4 bbl edelbrock. New prop is a turning point hustler. Hoping that I can get a bit more stern lift and bite. The 3 blade starts to break loose at 4900, I feel like I should be able to trim it more. I want low end skiing grunt, don't care too much about top speed. Should be getting my O2 exhaust spacer today, and have a wideband O2 sensor/AF gauge ready to install to see if I can tune the carb a bit better. Wish I had access to a prop shop and a bunch of props to try...

Of course you do Nola. Totally forgot about your rather special set up. I was aware from previously discussing, just remembered.
Yeah. Had the exact same result around loosing grip with trim, on some of the props I’ve messed with on boats like these. The tempest is pretty good at holding on. The 4 blade ally props just won’t entertain it. Mostly the reason behind the results shown, given in the example I gave earlier. If you can get a hold of a tempest to try, I’d recommend you give one a go. Only down side is that they are a heavy big lump to swing. You shouldn’t have a problem I’d say though. Of all the props I’ve tried on boats like this and my own boat (18ft bowrider but with a v8 mpi)…it’s only the enertia prop that’s managed to better the tempest for top end…but can’t come close to being as good as the tempest for acceleration and cruising. Tempest is just in a league of its own, with a very unique ability to behave like a higher pitch than it is…when cruising in the 20-30mph range…displaying oddly low rpms compared to any other prop of the same pitch. It even manages to run less than the enertia of an inch more pitch, when in that speed range. Also very good at lifting the hull in general, I’ve found. Typically it will lift the hull quite neutrally. As in not particularly biased one way or the other, referring to bow lift or stern lift. Hard to explain, but I’m sure you get what I mean. Very central angle of lift perhaps. Compared to the likes of an enertia or laser very obviously biased towards bow lift…or a rev 4 (4 blade tempest) perhaps being more keen to lift from the stern (in my opinion at least).
Perhaps you’ve spoken to @jimmbo about his findings previously. I think he runs a rev 4 well on his boat. He has a powerful similar sized boat.
Mine is similar but heavier certainly…and has a stepped hull with a pad. Around the 300hp mark. Always run a 3 blade on her. Laser 2, tempest and enertia most often. Had a ballistic on her years ago. That did well top end…but nowhere else.

 

[jimmbo]

Perhaps you’ve spoken to @jimmbo about his findings previously. I think he runs a rev 4 well on his boat. He has a powerful similar sized boat.

I run an Enertia, and have a couple of RAKERs for spares
I would scuttle my boat rather put a 4 Blade on it

 

[QBhoy]

I run an Enertia, and have a couple of RAKERs for spares
I would scuttle my boat rather put a 4 Blade on it

Ah. Fair play. So you do. Who am I thinking of that runs a rev 4 on a 18/19ft with an upgraded 4.3 or small v8 ? Can’t remember now. Burst out laughing reading that post there. Brilliant and agree.

 

[nola mike]

Ah. Fair play. So you do. Who am I thinking of that runs a rev 4 on a 18/19ft with an upgraded 4.3 or small v8 ? Can’t remember now. Burst out laughing reading that post there. Brilliant and agree.

I'm going to start a new thread in the prop section to keep from totally hi jacking this thread

 

[BCran]

Thanks for the replies, my primary concerns are that either the engine has an issue by not making power with the factor 14x23 three blade prop or that I may be over loading (tasking) the engine. This evening the water was flat/calm and I tried both the 14x23 three blade (that it came with when i bought it) and then the new four blade 14x23. The three blade ran horrible, switched to the four blade and performance improved to 4,100 rpm a d about 40mph. The three blade would only run 30mph @ 3500rpm. I did not think the three blade had prop hub spin, but now it seems almost certain it does. I'll get a new one and see how that goes. Again thanks for the replies.

I am puzzled by the performance you are reporting. It sounds like we are running very similar boats, engines and prop set up. I would think that it’ll your prop was spinning on the hub, you would be over-revving. I’m not sure what happens when the hub spins since it’s never happened to me.

 

[BCran]

Hello, my 2010 Tahoe Q5i is only making it to 3500-3700 rpm and tops out about 32mph WOT and trimmed with just me in the boat (215lb). 4.3l carburated 190hp with stock 14x23 three blade prop. Tried a new 14x23 four blade (should be a 14x21) but results roughly the same. Prop hub is good (no prop slip). Boat is new to me but from what I have read should be making 4400-4800 rpm and at least 40mph. Any ideas?

Ohaze,
Do you have any idea how many hours may be on the engine? Have you done any compression testing? Simple to do and may provide some insight into the problem. Just out of curiosity, where are you located?