Engine rpm question while driving.

Big-E

Petty Officer 2nd Class
Joined
May 2, 2005
Messages
135
Hey guys this post below accually almost aplies to myself. http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=24;t=003719 <br /><br />My new motor will not rev over 3300 rpms. Im sure tach is dead on cause when i rev her out of the water she will rev to 4 grand very fast. I try not to do that much cause she only has baout 9 hours on her now. I have only been cruising between 2600-3300 rpms anyway which is 30/32 mph per gps. The hole shot isnt very good with 4 adults in the boat but will get up in about 6 seconds. <br /><br />Sunday while we were comming back in threw the pass there were solid 3-5 footers and the boat had trouble reving up in that slop. Again we had 4 adults on board. The motor did sound like it was straning more then she should so like the previous post im wondering if some bozo put a v8 drive in my boat. When i got the boat the drive was laying on the deck of the boat, the prop has no #'s on it. Can a prop shop tell me w hat pitch/diamiter prop i have on there now? Tomorrow i will open up top of drive and count the teeth. How many teeth should i have for a 3.0 L Mercruiser and how many should there be for a v8 Mercruiser. <br /><br />Thanks in advance guys, <br /><br />Big-E<br /><br />BTW. the boat is running great and we got her nice and bloody on sunday.
 

tommays

Admiral
Joined
Jul 4, 2004
Messages
6,768
Re: Engine rpm question while driving.

big <br /><br />i have a 1995 3.0LX on a 20 ft boat if i have 4 people on board and want to have a good hole shot i use a 15 x 17 which gives me 27 MPH at 3800 rpm and i can go through the nasty slop with plenty of power <br /><br />if i am running a light load i have no problem with a 14 x 19 at will see about 41 to 42 mph at 4800 RPM<br /><br />i have a 14 x 21 and it pretty much kills the boat unless i toss everything overboard but 5 gallons of gas <br /><br />if your GPS and RPM is correct than something is not right i would find out the size of the prop before you pull the cover off the drive
 

Big-E

Petty Officer 2nd Class
Joined
May 2, 2005
Messages
135
Re: Engine rpm question while driving.

thanks tommays, Another question for ya. Do you think my motor has enough hours on it to pull wot? It has just shy of 9 hours on her right now. I'll take that prop off and have a shop look at it tomorrow. Im sure the rpm is right and the gps is within 2/3 mph of speedo and within dads boat's speedo and same as his gps. I gota say that slop made it very hard to get her on plane again after id slow down for a roge wave. <br /><br />thanks again, <br /><br />Big-E
 

tommays

Admiral
Joined
Jul 4, 2004
Messages
6,768
Re: Engine rpm question while driving.

it should run at full rpm but i would not do it much until after 20 hours<br /><br />i dont like to run mine WOT for more than 30 seconds it really is not built out of high performance parts<br /><br />tommays
 
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