77 Evinrude 115 HP running strangely

[Basscat 1]

Re: 77 Evinrude 115 HP running strangely

I installed a SE Sport 300 Hydrofoil to my boat and I am very pleased with it. I sacrificed top end speed and fuel economy, but my boat handles much better. Before I had a porpoising problem which would make the rpms fluctuate in the mid to WOT range. While the prop is not actually leaving the water, I was having a cavitation problem. All I am saying is that you may be having the same problem.<br />Check this out. http://www.overtons.com/modperl/overtons/detail/pdetail2.cgi?r=detail_view&item_num=28983 <br /><br />

 

[piniongear]

Re: 77 Evinrude 115 HP running strangely

If you go to a shop like Baumann Marine (in Houston TX) they can check your prop hub with a torque wrench while you wait. It's either good or bad.<br /> As far as the pitch goes, you want to put as much pitch on that prop as it takes to limit the top rpm to 5500 on the 115. That is the great value in a tachometer. Without one, you are just guessing. You can find some reasonably priced tachs on Ebay. I know because I just bought a brand new Faria 7000 rpm tach for under $30 two weeks ago. <br /> Hang in there.................piniongear

 

[RustynHouston]

Re: 77 Evinrude 115 HP running strangely

thanks guys, I'm learning alot. <br />My prop shop checked and the hub was not spun. They say the tachometer is needed to make sure exactly what my problem is.<br />From OB's post above and another I read elsewhere in this forum, I think I am overpropped and cavitating. The other post mentioned that the condition COULD cause an increase in propeller speed and if not addressed, could overheat the outboard. <br />I'm going back to 17 pitch AND getting a tachometer, probably this weekend.It worked fine with a 17 before and I'll never change pitch again. "If it ain't broke don't fix it!" is now my latest moto. Having no previous experience in boating, I had no idea a pitch change could cause a cavitation problem.<br />I really appreciate this forum and all the input.

 

[piniongear]

Re: 77 Evinrude 115 HP running strangely

When you get the tach, I think you want to set the selector dial on the backside to '6' for your 115 engine. Perhaps other members could verify that setting. You will be glad you got a tach because then you can tell what the engine/prop combo is doing.<br /> I would suggest buying the tach FIRST and trying out the 19 inch pitch. Then try the other prop. Whichever selection gives you 5500 rpms at full throttle is the correct choice.

 

[RustynHouston]

Re: 77 Evinrude 115 HP running strangely

copy that

 

[tabbott]

Re: 77 Evinrude 115 HP running strangely

Hey Pinion Gear,<br />What would my 1993 40 hp wot RPM max need to read on the tach.

 

[piniongear]

Re: 77 Evinrude 115 HP running strangely

I am not sure about max rpm on a forty. Perhaps another member has the info. Another way to get this is just call a local dealer in the morning and ask. It is pretty standard on each model of engine.

 

[RustynHouston]

Re: 77 Evinrude 115 HP running strangely

I wanted to verify that going back to a 17 pitch prop eliminated cavitation problem.<br />thanks all!

 

[Dhadley]

Re: 77 Evinrude 115 HP running strangely

For maximum engine life and best all around performance your target rpm, with an average load, is 5800.