Motor or Outdrive???? - Maxum Boat Owners Club

Lake Murray Maxum · 03-23-2011, 03:54 AM

Took the fam out on the lake for a nice dinner to enjoy the beautiful SC weather. The boat ran great on the way out. On the return trip, sad face. My boat normally runs approximately 46mph at full throttle (5.7L/Bravo3.) at full throttle, I only got up to about 32mph. The engine sounded a little bit louder than usual. Rpm's seemed to be normal. It had been winterized up until last Sat. And it ran well, no issues. Anybody have any ideas so that I can be prepared? Taking it back out tomorrow. Thanks in advance

shrew · 03-23-2011, 01:31 PM

Headwind, opposing current or tide, or heavier than normal boat load (e.g. more guests than normal)? How were the engine temps? what about RPM's? Certainly speed is important, but I'm curious if the RPM's were coming up to the Max RPM range during the same time period. How was speed being measured? Speedo or GPS?

seapuppy · 03-23-2011, 02:04 PM

could be alot of things...since the load was the same coming in as going out...that's probably not it..however it could be bad gas....it sat for quite awhile and gas can be bad.......I'd run it some more and then refill the tank...go back out....see if that doesn't fix it...also if it does it again...check the gas cap..open it up while idling..if you hear a hissing sound when you open it...that may mean the vent maybe blocked or clogged by a mud dobber or some other critter..

SP

biggerseagar · 03-23-2011, 02:48 PM

When is the last time you changed your impellers? You have B-2"s right..........Instead of pumping water your pumping air. I didn't notice the diference in sound while running until my wife said something............

Roger

ss3964spd · 03-23-2011, 03:10 PM

Quote:

Originally Posted by Lake Murray Maxum

The boat ran great on the way out.
My boat normally runs approximately 46mph at full throttle (5.7L/Bravo3.)
at full throttle, I only got up to about 32mph.
The engine sounded a little bit louder than usual.
Rpm's seemed to be normal.

What was the RPM reading when you were doing 32 at WOT? In other words, were the RPM' normal while running at 32, or were the RPM normal for WOT but still only running at 32?

Dan

seapuppy · 03-23-2011, 04:20 PM

I doubt with any outdrive will pump air up into the engine would affect the rpm/speed of the boat..that usually is indicative of high temps...no cooling water getting to the heads....we need to understand what his wot is on the engine and what his speed is...if his speed is reduced yet he's reaching wot...then most likely he's spun a hub........

SP

Lake Murray Maxum · 03-24-2011, 01:25 AM

Thanks for all the feedback! I was wot when I hit 32mph on return to marina. In my instant panic I noticed my rpm to be around 5000. When boat is functioning normal at wot, rpm are around 5000. I was gauging speed by speedometer. The impeller was replaced in spring 2009. Only about 40 hours on it. I wasn't able to get the boat out today because of 30mph winds but am hoping to get it back out within next couple of days. I will report back in once I get the boat back out of the marina. Thanks all and I appreciate it.

seapuppy · 03-24-2011, 03:32 AM

what's the pitch of the prop.???...sounds to me like a spun hub personally..

oh..and welcome to the zoo..

SP

ss3964spd · 03-24-2011, 03:01 PM

Yeah, if RPM's were actually at 5K, and you were only running at 32, sure sounds like you may have spun a hub.

Although I've never spun one I'd think it should be easy to verify: From a stand still throttle up hard. If the hub has spun you'll see the RPM's jump but there won't be a cooresponding increase in speed.