High RPM's

[Bryce2004]

Hello, I have a 2007 Mariah with the 3.0 mercruiser, last season the boat would run at 4600-4800 WOT and 42MPH. I too the boat out today for the first time in two months and at WOT I'm pushing 5400-5600 RPM's - what could cause this issue?????

 

[NHGuy]

Re: High RPM's

Hub/Prop slip, tach error, trim position, different prop. Is the same prop on there?

 

[fat fanny]

Re: High RPM's

Mark the prop to it's hub with a paint marker and see if the mark stays constant and or moves or breaks if so hubs slipping and don't let that thing go that high on rpms. And if the marks don't move double check your tach with a verifiable shop tach.

 

[Bondo]

Re: High RPM's

Mark the prop to it's hub with a paint marker and see if the mark stays constant and or moves or breaks if so hubs slipping and don't let that thing go that high on rpms. And if the marks don't move double check your tach with a verifiable shop tach.

Ayuh,... If this checks out,...

Try a different Tach...

 

[Don S]

Re: High RPM's

4600-4800 WOT and 42MPH. I too the boat out today for the first time in two months and at WOT I'm pushing 5400-5600 RPM's -

You don't mention how fast you were going at those 5400 rpm, if you were on plane, then it's not a prop hub problem, a spun hub in the prop or coupler would give you 1 or 2 mph at best. If you were on plane, then you either have a tach issue, or the blades of your prop are damaged.

 

[Bryce2004]

Re: High RPM's

You don't mention how fast you were going at those 5400 rpm, if you were on plane, then it's not a prop hub problem, a spun hub in the prop or coupler would give you 1 or 2 mph at best. If you were on plane, then you either have a tach issue, or the blades of your prop are damaged.

Don S. At 5400 RPM's I was around 25 MPH the but was on plane. Would a tach just go bad, also the prop is in the exact same shape as last season - please advise

 

[Bondo]

Re: High RPM's

Don S. At 5400 RPM's I was around 25 MPH the but was on plane. Would a tach just go bad, also the prop is in the exact same shape as last season - please advise

Ayuh,... Unless you happened to forget the leave the trailer in the parkin' lot,...
Do the Prop Test as stated above,...

If your Lucky, it's a Prop problem...

 

[Don S]

Re: High RPM's

You have a tach problem, and yes they go bad just setting.

 

[Bryce2004]

Re: High RPM's

You have a tach problem, and yes they go bad just setting.

Don S. If by chance it's not a tach or prop issue where else should I look??? Thank you

 

[Don S]

Re: High RPM's

Don S. If by chance it's not a tach or prop issue where else should I look??? Thank you

I have no idea, unless you have a trim gauge that is out of adjustment and you watch that gauge and adjust the trim by the gauge and not by how the boat feels. If you do run by gauge alone, and it's off, the drive may be trimmed to high, you would then have higher rpm and lower speed. If you aren't sure, try it again, and trim the drive down some and see what happens.

 

[toolsinbox]

Re: High RPM's

Hasd to be something from the hub to the prop

 

[Don S]

Re: High RPM's

Bad gas maybe. gas filter? I am thinking a fuel issue here. Does it idle correctly? Any vacume leaks? If all this checks out ok You will be pullin the heads. I would think the valve train is suspect.

He is getting higher rpm and less speed. How could that be a fuel problem? If he had a fuel problem he would have less rpm, not more.

 

[toolsinbox]

Re: High RPM's

That post was for another thread. As i stated i bet its the hub

 

[honeys money]

Re: High RPM's

My tach is doing that, reads fast for about 30 min, then all good for the rest of the day.

 

[Bondo]

Re: High RPM's

My tach is doing that, reads fast for about 30 min, then all good for the rest of the day.

Ayuh,... If it's got the (4) (6) (8) switch on the back,...
Many times flippin' that switch back, 'n forth a few times, gives another life....

 

[Bryce2004]

Help needed I'm stumped

Help needed I'm stumped

I have a 3.0 mercruiser, I posted a few weeks back about having high rpms and low speed 5600 rpms and 25 mph. I purchased a new hub and prop now I'm at 5000 rpms and 30 mph it's getting better, but my normal range is 4600-4800 rpms and 40-41 mph what else could cause this issue

 

[Bondo]

Re: Help needed I'm stumped

Re: Help needed I'm stumped

what else could cause this issue

Ayuh,... You did leave the trailer in the parking lot, Right,..??

I don't remember yer Details Bryce,...
Could you Update Us, or link this thread to yer other thread,..??

 

[Bryce2004]

Re: Help needed I'm stumped

Re: Help needed I'm stumped

Bond-o
Heres the story, in November I ran my boat for the last time for the season everything was normal she ran at 4600-4800 rpms and around 40 mph. Two weeks ago I put her in the water for the first time this year and the rpms were 5600-5800 and the speed was around 25mph this is way below normal. Some of the members on the site said it may be the prop and hub. I replaced both lastnight and took her out this moring and she ran a little better at 5000rpms and 30 mph what am I missing and what else can I do. please help

 

[Don S]

Re: High RPM's

I am going to merge your two posts together. Your second post is nothing more than an update to your old post, not a new problem, so to keep from having to go through the full process again, it's just better to merge them.

I still think you have a tach problem.

 

[tswiczko]

Re: Help needed I'm stumped

Re: Help needed I'm stumped

You say you replaced the prop also, Are they the same style, pitch, diameter? if you have the old prop and it has a rubber hub you can get that hub pressed out and a new one installed fairly inexpensively