2010 Volvo penta 5.0 GXI-J 4400 rpm WOT knock and quick hesitation

[Tail_Gunner]

IT appears you need a new prop and its been cavitating a bit as to why that i do not know, Odd is that a spacer between your prop and drive or just the casting of the drive? Actually with the high slip your running its hard to pic a prop so to speak Do you have access to a loaner prop that is in better condition. Opps saw the second pic no spacer.

http://www.theguardian.com/science/...n-beginners-building-fastest-ship-world-video

 

[Mansourman]

Huh. Ok I get it. Thanks! Ok so what's the relationship in diameter? I looked at the three links and saw each prop has a different diameters? Also we just finished taking her out and testing again- she's hitting the rev limiter for sure... I guess that damn prop has been costing me for a while. I did notice the scag is bent slightly...

 

[Tail_Gunner]

There is very little effect on diameter, the mfg adjust the blade area and design. However the larger the diameter the more effective the prop become's at overall pushing at the cost of some speed...read big heavy boat's benefit generally from large diameter..If your boat can push that 22 four blade to 4900 repm i believe you will see a 57 mph wot and much more of a midrange punch.

 

[Mansourman]

Tail Gunner- is this a hobby or a living?

 

[Tail_Gunner]

Tail Gunner- is this a hobby or a living?

Hobby of course....and a bit of a sickness to tinker with boat's. A pro would have pointed out that most tachs are not precisely calibrated....notice the abrasion's and mottling on the leading edge of your prop those are cavitation burn's causing slip etc etc etc.

 

[bruceb58]

If you get a Volvo factory service manual and look at the prop chart for your 1.60 drive and a 14.5" x 21" prop, you will see the speed range will be between 49-55MPH.

You are in the normal range. I really doubt you have a cavitation issue.

My suggestion is to calibrate your tach and stop running it at 5000 RPM.

 

[Tail_Gunner]

Pic 2 you dont see the burn's on the leading edge of the prop Bruce...If you take all the information that the poster has given aka 50mph gps, Ecm is reading out 5000 rpm and a 1.6 ratio nets a 19% slip ratio that's very poor performance. I would be the first to agree to try a donor 22/23 and see the result's its quite possible a 23 would work quite well thats not a deep v and a 22 is not a large prop for a 21' boat with a fuel injected 5.0. To the OP Bruce is a very methodical and informed person.

If you take the slip down to 10% one get's 56 mph so perhaps a fresh 21 would be the prop of choice. But marine engines are very weak above 4500 rpm the fact a 21 turns that high even with slip is a good indication of under propping remember he is popping the rev limiter.

 

[bruceb58]

I agree with you that it might be worthwhile trying a 23" prop. Depends on what the performance he has now with the 21" when the boat is full loaded with gear and people.

 

[Mansourman]

Guys- great info. I'm leaning toward the 4 blade 22P. The rev limiter seems to kick in at about 80% throttle. I'm guessing I've got at least 5200 with a 21P and a 22 would cost me 200 rpm and the 4 blade would cost me another 200 rpm- thoughts?

 

[Tail_Gunner]

Yes it should be a very good pick Check your PM's..What iboats are you no longer carrying the Stilletto line gesssh. Not that the Solas is a slouch by any mean's

 

[89retta]

Just read your thread. I had the same problem. Bought an 04 Caravelle 187 with the 4.3 Volvo GXI. When I took the boat for a test drive it was hitting the limiter. That's what the guy told me was the noise and engine cut out. Had it put on the bill of sale subject to inspection. Inspection was great and it was the limiter. He had a 17" 3 blade stainless on it. Tried a 19" stainless still was hit the limiter. Bought a high 5 21" way better but could still hit the limiter. Ended up with a 4 blade Apollo xhs 20". Problem gone. Just a matter of finding the right prop. Even though the Apollo is small in pitch and only has 4 blades its about an 1.5 inches larger in diameter which is why I think it brought the rpm's down

 

[Mansourman]

Ok guys- it's been a while but unfortunately I'm not retired yet. So a couple of things- I did end up replacing the high pressure fuel pump as a JIC because I wanted to try to do everything to rule out detonation. I DID buy the 4 blade 22 pitch prop that tail gunner recommended and I gave her a try. So now it seems that WOT has been reduced to 48 MPH and the prop seems to lag. I put the 3 blade 21 on and WOT was the same?? Quicker hole shot though (all stainless props). I checked a stingray website for a 21' boat similar the my crownline 21 LPX SS and it is indicating a 21P SS prop tested at 55MPH. So- I'm not sure what happened but it definitely isn't hitting the rev limiter anymore. Another thing I noticed is that the RPM gauge use to indicate 4400 when we were hearing the pop. Now the gage barely reads above 4000 with the 3 blade 21P and the 4 blade 22P- strange. Maybe I did/undid something?

 

[89retta]

I would check your tach. Sounds like its off by 1000 rpms. Rev limiter should kick in around 5200-5400. Mine was doing the same thing and my tach was off. Funny how we both have the exact same problems. Hope you get yours figured out like I did.

 

[Mansourman]

I was thinking it might be the tac too- but 48MPH doesn't seem to equate with 5000 RPM with a 22P prop. Unless you have +20% slip- which seems excessive with my hull. Seems slow...

 

[Mansourman]

so if the tac is 1000 rpm off then then 5000 rpm 1.6 ratio 22pitch at 48 mph is a 27% slip
but if i back the numbers into the rpm 1.6 ratio 22 pitch at 48 rpm with a 10% slip then i calculate 4096 rpm which is exactly what the tac reads- i guess i'll go get a tac down at the auto store and verify...

 

[Tail_Gunner]

Ok guys- it's been a while but unfortunately I'm not retired yet. So a couple of things- I did end up replacing the high pressure fuel pump as a JIC because I wanted to try to do everything to rule out detonation. I DID buy the 4 blade 22 pitch prop that tail gunner recommended and I gave her a try. So now it seems that WOT has been reduced to 48 MPH and the prop seems to lag. I put the 3 blade 21 on and WOT was the same?? Quicker hole shot though (all stainless props). I checked a stingray website for a 21' boat similar the my crownline 21 LPX SS and it is indicating a 21P SS prop tested at 55MPH. So- I'm not sure what happened but it definitely isn't hitting the rev limiter anymore. Another thing I noticed is that the RPM gauge use to indicate 4400 when we were hearing the pop. Now the gage barely reads above 4000 with the 3 blade 21P and the 4 blade 22P- strange. Maybe I did/undid something?

I assume you bought the Solas 4 blade ss, Can you get your hands on a accurate tach google tiny tach and do a run with the 22 i am sorry about the pick that 21 on the boat must have been in bad shape. Is it returnable if not i may have a home for it if you need one.

 

[Mansourman]

Hey Tail_Gunner. Yes I got the Solas. No worries - like it- it runs smooth and mid range is pretty solid. If I try another prop and it works out better I'll check in with you on a home for the Solas. I'm not really sure it's the prop. I had the high pressure fuel pump changed just in case- was 47PSI, now it's around 58PSI. I just took a look at the tiny tach and ordered one. I'd like to play around with this a little more to see whats really going on with her. Just seems a little off but I think that RPM gauge will shed some light. Thanks for replying and the help- I'll update you guys...
Sincerely,
Chris

 

[Tail_Gunner]

58 psi wont work are you somewhat mechanically inclined???? Hmm let me check on something you have a very recent efi system it is mpi mult port that is.