Merc 115 4-stroke prop/power issues

duncc

Cadet
Joined
Aug 3, 2008
Messages
22
Hello All,

I have read through these forums a lot over the last year and have posted a few times and received a lot of help from the people on this board. I am still having issues however and would like to get some more opinions.

I have a 2006 Lowe FS175 alum fish and ski with 06 merc 115 4 stroke. Bought last summer, motor was a total dog, followed advice on engine height prop pitch etc. from forum members.

Motor came from factory in lowest position. I moved the motor up one hole at a time until I found the best position for hole shot, top speed, cornering etc. I have now tested the boat in every available motor height position and currently have it mounted in what feels like the best position. (CAV plate just above water when boat is on plane.)

Hole shot was still not acceptable, tried a Turning point hustler 17 pitch, improved but still not great. (I still can't get up on a slalom ski, and yes I am an experienced skier with proper technique.) I went to a 15 pitch hustler, huge difference in hole shot but the thing overrevs like crazy and tops out at 35-36 mph. Also tried a 15P express stainless and it was worse than the hustler for hole shot.

17P holeshot is horrible; 43mph @ 6000 rpm
15P decent holeshot; 35mph @ 6000 rpm

I can get up on the ski with the 15P but once I am up the boat won't pull me fast enough for a good ski.

I am getting extremely frustrated, this motor seems so underpowered (used to have a 1990 18' bayliner with 3.0 liter I/O 120 hp and it seemed better.) I talked to turning point and he said the 115 4S merc does not have a good holeshot.

My questions are:

1. Will this motor get noticeably stronger the more it breaks-in? It's got between 30 and 40 hrs on it.

2. Is there a prop out there that anyone can suggest that can help me?

3. Can I put a larger motor on the boat than it is rated for? (115 hp feels ridiculously under powered.) i.e. a 135 optimax?

4. What about the 115 opti, would that fix my problems?

Thanks for all your input, I know this was an essay to read. I am really getting discouraged; I love the boat but the motor is such a dog it's depressing.
 

duncc

Cadet
Joined
Aug 3, 2008
Messages
22
Re: Merc 115 4-stroke prop/power issues

The other odd thing is that my motor will rev up to 7000 rpm on the tach with no alarm buzzer or rev limiter kicking in. I realize the tach may be wrong but it seems right when at idle.

I really just don't know where to even go from here.
 

199675hpforce

Petty Officer 1st Class
Joined
Feb 27, 2004
Messages
299
Re: Merc 115 4-stroke prop/power issues

Wow funny how all the boat dealers say how great 4 strokes are lol. I just bought a similar boat crestliner superhawk 1700 with 115hp mercury 2 stroke. My boat is heavier and bigger and im hauling *** in 2 seconds it jumps to 30mph hits 40 quick tops out 43 to 45mph at 6500 altitude running 19pitch prop 4750rpm. Just ordered a 17pitch to pickup 500 rpm. Your motor sounds pretty weird and slow. If you purchased new maybe you can trade for optiblow or yamaha 2stroke?
 

duncc

Cadet
Joined
Aug 3, 2008
Messages
22
Re: Merc 115 4-stroke prop/power issues

Yes it is very frustrating that my dealer pushed the 4 stroke saying it will have tons of power in comparison to my old boat. I guess I should have used my common sense and realized a 1.7L inline-4 isn't going to be very torquey. Is your motor an optimax??
 

199675hpforce

Petty Officer 1st Class
Joined
Feb 27, 2004
Messages
299
Re: Merc 115 4-stroke prop/power issues

Mine is 2000 carb 115hp with oil injection removed. I was running a 19pitch at 6300 altitude. If you want better engine try evinrude etec people love those. Wonder if your prop is slipping on shaft, 7000 rpm seems really high.
 

Swishguy

Seaman Apprentice
Joined
Jun 27, 2004
Messages
43
Re: Merc 115 4-stroke prop/power issues

I have a 19' lowe deck boat that originally came with a 115 merc 4 stroke. It was kinda gutless & all I saw was 37 mph at 6300 rpm with a 14X13 prop.
I switched to a 150 e-tech & holy schnikee. Holeshots are amazing & top end is now 52 mph. Cruising rpm,s are also way down!
 
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