Question for DHadley and/or other lower unit experts

[badjohnson]

i got a new lower unit for my 2001 johnson 150. thanks for your previous responses.<br /><br />question: with old lower unit i was getting approx. 4900 rpm's and 49 mph. with new lower unit (same prop) i get only 4700 rpm's<br /><br />what do you think? is new unit geared differently? mechanic says he didn;t change engine hieght or anything so i;m not sure. also, since new unit while on plane the engine kicks back a splash of water onto transom seats. this didn't happen before, maybe not related. in any case i probable need to raise engine. what do you think?

 

[Dhadley]

Re: Question for DHadley and/or other lower unit experts

I think it may be related. The water being kicked up is a strong indication that the motor was lowered or is too low now for whatever reason. Lowering the motor slightly would indeed be about 200 rpm.<br /><br />I guess its pointless to argue with him about if he moved it or not. Raise the motor and I'll bet both situations correct themselves.<br /><br />Good luck!

 

[DJ]

Re: Question for DHadley and/or other lower unit experts

Forgive me for jumping in here.<br /><br />Even if you do gain a couple hundred RPM's, 4900 is still WAY too low.

 

[Dhadley]

Re: Question for DHadley and/or other lower unit experts

Oooops!<br /><br />Good catch DJ. I cant believe that got by me. We're headed to the Keys in the AM -- no wonder I'm not thinking straight. <br /><br />Youre right, we're 1000 low no matter how ya cut it. The new gearcase should be the Lightning design but should only be better.<br /><br />Are we sure the tach's correct?

 

[badjohnson]

Re: Question for DHadley and/or other lower unit experts

yes, i plan to raise it and try to get rpm's where they should be. not sure if tach is correct, how would you chack it and shouldn;t i get around 5500 rpms?<br /><br />i will raise and then maybe look at look at new prop.

 

[DJ]

Re: Question for DHadley and/or other lower unit experts

At least 5500. The only way to check the tach is with another one.