rpm\wot for 70 hp

river37091

Seaman Apprentice
Joined
Feb 21, 2004
Messages
36
this is a 1988 70 hp.friends boat.he says it never runs over about 4000 rpm at about35 mph.boat is stratos 259v 16 ft.any ideas?thanks roy
 

ob15

Chief Petty Officer
Joined
Jan 4, 2004
Messages
514
Re: rpm\wot for 70 hp

Does he not run it over 4000 or will the motor not go over 4000? If it doesn't go over 4000 then somehting is wrong. I'm sure I will be corrected if wrong but he should be able to get 5800 with a normal load.
 

rickdb1boat

Supreme Mariner
Joined
Jan 23, 2002
Messages
11,195
Re: rpm\wot for 70 hp

Ditto on the 5800...Although I doubt he would be hitting 35 MPH at 4000..
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: rpm\wot for 70 hp

Did it ever go to 5800 on that boat?<br /><br />If not, it is probably a prop selection problem.<br /><br />If yes, he has an engine problem.<br /><br />We need to know more.
 

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: rpm\wot for 70 hp

35mph at only 4-grand might point to the tach being incorrect. Make sure it has the setting for 3-cylinder models.... Don't go tearing into the engine checking the switch setting on the tachometer....<br />- Scott
 

rickdb1boat

Supreme Mariner
Joined
Jan 23, 2002
Messages
11,195
Re: rpm\wot for 70 hp

Must be set to "6" pole on the back of the Tach...
 

river37091

Seaman Apprentice
Joined
Feb 21, 2004
Messages
36
Re: rpm\wot for 70 hp

will check the tach and get back to everyone.thanks
 

river37091

Seaman Apprentice
Joined
Feb 21, 2004
Messages
36
Re: rpm\wot for 70 hp

tach is on 6 pole.put a tail on it.will run it and leut u know what tach reads
 

rickdb1boat

Supreme Mariner
Joined
Jan 23, 2002
Messages
11,195
Re: rpm\wot for 70 hp

I still believe it's Tach related error. But also let us know where the cavitation plate is in relation to the bottom of the hull. Higher/ Lower....And, what size and pitch prop are you running now? I doubt another prop is gonna get you another 2000 RPM's, so there is still a problem somewhere else..
 

river37091

Seaman Apprentice
Joined
Feb 21, 2004
Messages
36
Re: rpm\wot for 70 hp

ok everyone,thanks.put a tail on it and to the lake we went.ran fine good hole shot and speed.my friend wasn't trimming the boat all the way out.2 people and full tank 5400 rpms.is that about right?thanks again for all of your help.
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: rpm\wot for 70 hp

Start by raising the motor some. You're still about 500 rpm short.<br /><br />Is this a Teleflex tach?
 
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