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Author Topic:   Merc 115 4 stroke
kysard posted 06-21-2002 05:46 PM ET (US)   Profile for kysard   Send Email to kysard  
Does anyone have experience with this 115 EFI 4 stroke engine? Does it idle slow enough to troll? Reliable?
Clark Roberts posted 06-21-2002 10:09 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
I have a 115 Merc 4s on my 1979 Revenge 21 and find it to be very smooth, quiet and economical. Yes, it will idle low enough to troll at about 700 rpm (idle is ECM controlled and there are no timing adjustments). Happy Whalin'... Clark... SCN
jimh posted 06-22-2002 12:33 AM ET (US)     Profile for jimh  Send Email to jimh     
From looking at the specifications, the Mercury 115 shares the same power head with the 75 and 90, but the displacement has been increased by lengthening the stoke.

It appears that this same powerhead is used on the Yamaha 100 and 80-HP engines. (Maybe on their 115, too?).

The lower units appear to be different as the Mercury differs from the Yamaha by weight and gear ratio.

Clark Roberts posted 06-22-2002 11:09 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Merc and Yam 115's are virtually identical... power heads and lower units are same but mid section (exhaust tuning and trim/tilt) and cowlings are different. Mercs version is rated at 3 stars for emission (highest rating) while Yamaha's version is rated at two stars... most likely the ECM's are reason for difference... Maybe someone knows for sure... Yamaha uses Merc's corrosion resistant painting technique but don't know if they use it on all hp models... apparantly they don't use it on their trim/tilt units! Happy Whalin'... Clark.. SCN
tabasco posted 06-23-2002 08:40 AM ET (US)     Profile for tabasco  Send Email to tabasco     
Clark-
What prop are you running on your 115HP SS? what size? Have your tried the 18 pitch?
Clark Roberts posted 06-23-2002 02:12 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Tobasco, I'm running a 3 blade, 15" pitch Stelleto prop and it swings it at 5800 rpm trimmed out... top speed was 40mph back in April (cooler weather) and now with hot weather top speed is 38mph... accelleration is smooth and strong and it will hold on plane at 3200 rpm and about 14mph. I'm using a Doel-Fin and have a Bob's machine (6"setback) power jack plate. My goals with this set-up are slow speed planing and shallow water running and it works fine for me. I tried several props and it wouldn't swing an 18" pitch... Clark... SCN

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