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| RPMS https://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=7913 |
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| Author: | flaMtneer [ Sat Jul 02, 2011 12:13 pm ] |
| Post subject: | RPMS |
'99 234 Funship, VP 5.7L Gsi, SX Had a blown head gasket repaired - finally got boat back after about 6 weeks. They replaced head gasket, did some valve work, new water pump, t-stat, some hoses, adjusted throttle cable, etc. Took boat out one evening last weekend to check out and boat ran great, engine sounded great, no issues...except that I don't seem to be getting the same speed (GPS) at the RPMs that I was getting before. Nothing was done to the drive or prop. I had remembered getting approx 30 mph at 3000 rpms and I am now getting 30 mph at approx 3500 rpms. I pulled up the FW specs for my boat/motor and they agree with my memory and not with what I am now getting. Anyone have any thoughts on this? Seems very odd (if not impossible) to me. I can't get out this weekend, but I'm going to go out next weekend and re-check and make sure it wasn't my imagination. |
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| Author: | DaleG [ Tue Jul 12, 2011 8:50 am ] |
| Post subject: | Re: RPMS |
Memory is a great thing. I have had the same experience -- remembered boat once did 30 at 3000 --- now 30 at 3500. Here is my take -- the original memory was when boat was new (to me) and lightly loaded. It may also have been when weather is cooler. My boat now has tons of crap in it -- ski's / tubes / lot of life jackets and ski jackets/ a few fishing poles/ extra tools / spares/ two anchors/ and a lot more fuel probably than when I first got the boat. Combine all that with Florida summer weather and things change. With added weight, and less horsepower due to summer I think that is my difference. Maybe it is your also. |
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| Author: | DaleG [ Tue Jul 12, 2011 8:59 am ] |
| Post subject: | Re: RPMS |
thinking more --- it would have to be weight --- the engine and the prop are tied together RPM wise (assuming the props are in the exact same condition-- if they have ever been rebuilt that changes things) but weight affects the prop slip --- if the boat weighs more it will go slower for a given RPM if the engine is not making HP it just takes more throttle and a richer mixture to make the HP required to turn the engine a certain RPM so it should be weight |
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| Author: | flaMtneer [ Thu Jul 14, 2011 8:51 pm ] |
| Post subject: | Re: RPMS |
Thank Dale. Turned out that the RPM gauge was not reading correctly. Weird cause it was at lower rpms and it was consistent in it's wrong reading. When I want out last weekend I was pulling away from the dock and the gauge jumped to 4500 RPM - tapped it a couple times and it returned to normal and was back at 3000 RPM at 30 mph. Now that was the good news....bad news was after about 3 hours of flawless running it developed an issue at idle/low thottle - surge in idle and stalling. Seems fuel or fuel system related - in the shop now. It's been the season of maintenance - I've had the boat in my possession about 4 weeks since the beginning of April. The rest of the time in the shop! Trying to look on the bright side - not much left to fix and boat should be pretty much new again when all's done.... |
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