another RPM ? OMC 3L...

[G. Arruda]

I Know this has come up several times, but I still need some guidance. What else has the most bearing on RPM at WOT?<br />Boat's a, 16' 88 4Winns OMC 3L, prop 14x17 alum. Runs well, idle is a little rough, WOT speed is +-35mph BUT the RPM is only 2500-3000rpm. Fresh water boat, light load, overall very good shape. ???<br />Thanks for any ideas, Gary

 

[tommays]

Re: another RPM ? OMC 3L...

i think its unlikely your tack is correct most 3.0 will not push a boat at 35 mph at 3000 rpm you would be doing good to get 40 mph at 4800 rpm<br /><br />step one would be to use a shop tack to see what the real rpm is and work from there<br /><br />tommays

 

[waterone1@aol.com]

Re: another RPM ? OMC 3L...

I'm with tommays, that tach cannot be right. Get a shop tach and check it. As a side note, if you find your dash tach to be reading incorrect, before you pitch it or replace it. Take a look at the back of the tach and see if it has a small switch that selects between 4,6 or 8 cylinder. Move the switch settings a couple of times then set back to the proper setting. I have seen these switches get "flaky" and cause bad readings.

 

[idaho_rmk]

Re: another RPM ? OMC 3L...

I agree, check the tach. But correct me if I'm wrong. wouldn't a 17 pitch prop make you go faster than a 15 pitch at a lower RPM?<br /><br />I have the exact setup. <br />1988 Four Winns 160 Freedome with 3.0L I/O.<br />I got 38.7 MPH(GPS) at 4800 RPM. This is with a 15 pitch prop at about 2000 feet above sea level with me alone in the boat on glassy water.<br /><br />I'm just thinking that the engine is doing it's darndest to turn that thing over but that is the best it will do. at my elevation my dealer says 15 pitch is correct. I don't know what the elevation is there.

 

[G. Arruda]

Re: another RPM ? OMC 3L...

Thanks guys, I'll check the tach. I have an old shop tach, it gets connected to the -+ posts on the coil,right? (it's been a long time). Also, what about timing, could that have somthing to do with it? idaho... I thnk thats right, the bigger the pitch the more water it moves, and in turn slower RPM. Hey, how do you like yours, I have the same boat, got it late in the season, but seems great! Have you had any problems?<br />Thanks again,don't know if I'll be able to check it till spring, it's gettin pretty chilly around here, had to close her up for winter.

 

[idaho_rmk]

Re: another RPM ? OMC 3L...

We got ours late in the season also. <br /><br />The second time out I drug the outdrive pulling it out of the water and now there is a slow trickle into the bilge. I tightened all the bolts I could get to but it still leaks. Sooo next spring I'll have to pull the motor to change the gasket on the transom. That's the only "problem" I've had. <br /><br />It seems to run real good but I did notice my rotor is loose. I started a thread about that if your interested. <br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=24;t=008974 <br /><br />Ours is red and came with full bow and cockpit covers as well as the full convertible covers in brand new condition. Very Nice.<br /><br />It's getting cold here too so mine will be going to bed as well. <br />Then I fire up Snow Machines. Makes winter easier to take.