OMC Slipping???

[250cam]

Good:<br />Boat motor: good strong '88 OMC 4.3 v6<br /><br />Bad: <br />Bought boat w/o an outdrive... tried puting on a 3.0 cobra outdrive with brand new 12.75 x 23 prop.<br /><br />Problem:<br />Cannot get boat to plane befor it "revs out". Feels like the prop looses grip with the water.<br /><br />My deductions:<br />A. Prop is too small to push boat to plane<br />B. Engine to outdrive coupler is bad<br /><br /> Question 1:<br />Does A or B seem right or is there another option I haven't looked into yet?<br /><br /> Question 2:<br />About coupler: if I find a used one, are they the same for all motors (2.3-5.7) or do I have to find one specificaly for a 4.3?<br /><br /><br />Sorry, I'm a farm kid not a marine mechanic. <br />Thanks

 

[Boatist]

Re: OMC Slipping???

My thought is you have the wrong gear ratio. A 3.0L has a lower gear than a 4.3L. It is like you are driving your car in low gear with large tires. You will raach red line before you reach 65MPH.

 

[buddyx1]

Re: OMC Slipping???

I do not know much about that outdrive but I have an OMC 4.3L and my prop diameter is 14in and a 19degree pitch. Maybe it is your prop size

 

[Boatin Bob]

Re: OMC Slipping???

There are different gear ratio's for those drives, the 3.0 has 21:18 lower and 13:26 upper, the 4.3 has 21:19 lower and 14:26 upper, you may be able to make up the difference with props but it will probably involve some trial and error. As for the coupler if you are spinning yours at high RPM you normally will smell rubber burning and you should see your water temp go up as the water pump is also slipping in the drive. The coupler PN for 3.0 is 983902 or 3853962 and is different from the others (probably different bolt pattern).

 

[250cam]

Re: OMC Slipping???

I didn't smell any burning rubber smell nor did I notice a change in temp (I didn't watch the temp gauge either though). But this boat came to me w/o the outdrive so the dammage could have been done before my time. If the coupler was "spun" would the boat have moved at all? <br /><br /> I'm currently searching for a 4.3 outdrive but should the 3.0 outdrive have been able to plane the boat out (18', all fiberglass, Sunbird) with the prop I have on? <br /><br /> Does anyone have the part# for a 4.3 coupler?<br /><br />Thanks for the input so far!

 

[Boatin Bob]

Re: OMC Slipping???

Yes you can still move the boat with a spun coupler, it's just a question of when the load on the coupler passes the point of give, could be at idle or at high speed depending on the condition of the coupler. PN for the 4.3 is 984290 or 3858437. What kind of RPM's did you pull, was the engine getting near it's recommended range somewher around 4400? If not then you may want to try a smaller pitch.