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| Re-Propping a 298? https://www.smwebhead.com/phpBB3/viewtopic.php?f=6&t=427 |
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| Author: | joetallyho [ Mon Sep 18, 2006 1:57 pm ] |
| Post subject: | Re-Propping a 298? |
I had some engine work evaluated (see other post on Too Much Engine Oil Causing Power Reduction). My mechanic just happened to have the Volvo Penta Field Tech person in the area. They took my 2001 298 out and ran it WOT. They mentioned that the engine RPM maxed out at 4500 when it should be 5000. He said this is an indication of a wrong prop size. This condition also means the engines are working much harder than needed and if left untreated, could shorten the life of the engine. I don't run WOT hardly ever, but I did notice that after trimming out the drives for the two times I have ever ran WOT, it never got above 4500RPM, but didn't know enough to know it should be running 5000RPM. The props were original from FW (I forget what the sizes are). I need to check my owners binder. Has anyone run across this issue? Are props sized for cruise or for WOT? If it turns out the props are wrong, will FW change them out for free? Joe |
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| Author: | jvalich [ Mon Sep 18, 2006 7:28 pm ] |
| Post subject: | |
Joe: First off, if the engines haven't been tuned, get a tune-up done. The other thing, assuming they are Duoprops, have each set reconditioned and balanced. It very well could be the pitch odf the props are off. Having mine balanced and checked really smoothed out my operation. The dealer in my area always send the factory props out for tuning, etc as part of a prep of a new boat. The service manager said she was amazed as to how "off" new props can be. |
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| Author: | joetallyho [ Tue Sep 19, 2006 5:03 am ] |
| Post subject: | |
John, You know me. Every new season - new spark plugs, distributor/rotor. Tune-up not the issue. I agree with getting the props reconditioned. They look and feel better than brand new. Not that either. Any duo-proppers out there who have gone WOT and noticed whether your max RPM is to spec? Spec is written right on the engine, right on the electronic box with the red breaker reset switch. For my 2001 5.7 Gsi DP, it reads 5000 RPM. the Volvo tech doing troubleshooting got only 4500 RPM. Joe |
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| Author: | jvalich [ Tue Sep 19, 2006 5:29 am ] |
| Post subject: | |
I hit 4800 with my 5.0Gxi DPs. Are they F5 or F4 sets? Also, many prop shops will be able to change the pitch of a set. Certainly cheaper than the replacement cost! |
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| Author: | joetallyho [ Tue Sep 19, 2006 11:36 am ] |
| Post subject: | |
The VP tech rep offered to send me two sets of props to try out. Wow! What great support I thought. But would require at least 3 haulouts (at around $300 each) and I would still have to pay for the props. Good suggestion on the pitch adjustment. Did not know you could do that. Are these props intended to be efficient and optimum for the full RPM range, at optimum cruise, or limited range around optimum cruise. I think I will e-mail FW to see what their engineers have to say. Joe |
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| Author: | jvalich [ Tue Sep 19, 2006 12:27 pm ] |
| Post subject: | |
They should be optimized for WOT. It's not that they recommend WOT running, it's more or less the load on the engine that is of concern. Running in the WOT band recommended by the engine manufacturer allows the engine to run within it's best load range at cruise (75% WOT) translating to the longest possible engine life. |
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| Author: | AlexJ [ Tue Sep 19, 2006 5:48 pm ] |
| Post subject: | Prop Size |
After I got a new engine put in my boat, the mechanic took it out on a lake test. The boat had a stainless steel prop, size unknown. The rpm's at WOT were 4300. The rated WOT for the engine is 4800. He replaced the prop with 16 X 19 size prop and it increased the rpm's by 500 to 4800, the rated WOT for the boat. All this is a bit over my head but I'd thought I'd share with you my experiance. Now I just have to figure out the proper trim for the max speed before I run out of lake. Which happens when I'm thinking too much. |
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| Author: | AlexJ [ Tue Sep 19, 2006 5:52 pm ] |
| Post subject: | Prop Size |
Check on that prop size. The one on the boat was a 14.25 X 17 and we went with a 15 X 17. Quite a difference for .75! |
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| Author: | joetallyho [ Tue Sep 19, 2006 7:40 pm ] |
| Post subject: | |
My Vista 298 has Duo Prop. According to the spec sheet, for my 5.7Gsi, they should be F6. I will have to check the boat to confirm it matches. I checked my VP owner's manual, it does state that max RPM is 4600-5000 RPM. So, should I worry that the VP tech says it should read 5000? But, he could only get 4500 RPM. The drives were coated with Chesapeake Bay "fur", full water, half holding tank, two adults, half tank of fuel. I know these affect speed, but RPM? Joe |
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| Author: | jvalich [ Tue Sep 19, 2006 8:13 pm ] |
| Post subject: | |
Yes it will make a difference. Also did he use the tachs on the dash? In order to get an accurate reading you can't use the ones on the dash. On my other boat, I used a timing light that also accurately read RPMs to set the timing. |
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