Hey Bob

[Rob LaMoy]

Just to tweak your melon.....

I run a '99 175 efi on my Ranger R83. 18'10". I USED to get 67-68 mph but now only 64-65 tops. I realize some of it might be from the engine wearing down, but I still have good compression on all cylinders. I want to say they all registered within a lb of each other at around 90 psi. Pretty sure I lost 2 mph when I had no choice but to run the devil's blend of ethanol in it. I use to gps the difference when I could get real gas. I have a Tempest 25 on it and now a 6" Atlas jack plate. I can't raise it much until I get a Bob's low water intake on it.



Question #1: Aside from getting real gas again, do you think I can expect anymore top end if I get my prop reworked?



#2: Can my 175 turn a 26?



#3: Do you think raising my plate will get me anymore top end? I have awesome hole shot and don't want to sacrifice it. Would a 4 blade be better from more lift?



Ideally I would like to repower with a new 175 Pro XS but that's not in the budget this year.

 

[Bob Bourget2]

Your speed loss is not from your motor wearing out. More likely due to e 10 fuel. Figure approx 3 percent less powerful than conventional gas, and about the same loss of fuel mileage. Prop re work? YES. That could mean a couple just waiting to arrive. Can you turn a bigger prop? Depends on where you're at now. Due to the junk fuel, it's recommended to prop right at the top. Raise the plate until you see either a drop in water pressure, lift, or speed. 15 psi minimum at anything over 5000 rpm. Make sure your bottom is straight...lol:blink:

 

[Greg. Avery]

Rob maybe you just put on some weight when you were in rehab LOL :wacko:

 

[Rob LaMoy]

Greg,

I lost 21 lbs!!!



Thanks Bob. I knew some of it was from e-10 but I have more loss than I can attribute to that. I will see if I can get the prop worked. I run at 5600 RPMs. I run right about 15 psi at WOT. I am getting a new impeller and thermostats this week. I am hoping that the Bob's low water intake will increase my psi as not only is the pump pulling but I am pushing water in through the nose cone when running as well.



And for those of you who doubt Mercs.....this old girl is very near or over the 1,000 hr mark and she is still firing on all cylinders and running in the 60+ mph range. TAKE THAT!!!



Merc = there and back again.

 

[Bob Bourget2]

Well, it sounds as though you are only 2-3mph off your best speed. Considering E-10 fuels are approx 3% less energy producing than the "good" stuff, we can assume that if your motor produces close to 200 horsepower at the CRANK {which it does}, it would mean an approx loss of about 6 horsepower. Every MPH is worth about 10HP. Bottom iregularities, prop dings, transducers, extra boat weight {which does happen}, added gear, the TIME OF YEAR you tested before and after, all have adverse affects. Consider this....just from spring to summer can result in a 15% {!}, horsepower loss. Add that to your E-10 fuel, and you are talking NEARLY a 20% loss....or about 40HP!! Staggering, but true. NOW...if 1MPH is worth about 10 horsepower......during the summer.....you could be off by 4MPH+/-.

When testing anything, consistency is paramount and must be done under {very} controlled parameters. 1000hrs? Shoot..it's just broken in....