What motor mount hole? Fishhawk/Superhawk

[CMunger]

I have a Merc 115 on a Superhawk 1700 (I believe that the Fishhawk uses the same hull w/different interior, so either , and it cavitates on sharper turns. My theory is that I should lower the motor a hole or two. Currently it's on the middle of the 5 holes. For anyone who runs these boats, what hole are you on? (Also prop model & pitch, I chewed mine up this weekend, no it cavitated before that, and I will be replacing it, and was toying with the idea of changing)

[CMunger]

ttt

[JimmerAB]

HI CMunger,

I also am running a 1700 Superhawk with a 115 (Ficht, tho...) My motor is mounted on the middle hole as well. I don't seem to have any problems when I turn sharp, but I'm also thinking of lifting it one or two holes. I noticed that my cavitation plate is about two inches below the waterline when up on plane, and my understanding was that the c-plate should be about equal with the waterline.

My motor is rated to run at 6000 rpm @ WOT. Right now, I can only make it to about 5200 rpm with a GPS speed of about 38 mph. I honestly expected more performance than that, so will now start experimenting with motor height, props, etc. What kind of speed are you reaching now with your setup? And at what rpm's?

I'm currently running a 17-pitch ported AL prop. Now, given my speed and rpm issues, I may have to try a 15-pitch in an attempt to increase my rpm's. What prop were you running before its' untimely demise? Good luck, and keep us posted.

Jim

[gunnar]

I am running a 1750 fishhawk with a 115 ficht and am also experiencing cavitation/prop blowout on turns. Have contacted my dealer and he said that they have been told to mount the engines so that the cavitation plate is at the level of the bottom of the hull or a little higher. Mine is mounted so that it can only be dropped one more notch. Hope that that will be enough to solve the problem. Its at the dealer now and hopefully they'll get it done before I leave for Canada on Friday.

[gunnar]

I am running a 1750 fishhawk with a 115 ficht and am also experiencing cavitation/prop blowout on turns. Have contacted my dealer and he said that they have been told to mount the engines so that the cavitation plate is at the level of the bottom of the hull or a little higher. Mine is mounted so that it can only be dropped one more notch. Hope that that will be enough to solve the problem. Its at the dealer now and hopefully they'll get it done before I leave for Canada on Friday. Should add that I'm running a 12 3/4 x 21 prop.

[CMunger]

I'm running a 13x19 prop on my Merc 115, and I've been getting (w 2 adults) about 42-43 @ 5200 RPM GPS. I think the theoretical is 45, so I was happy with that. I'm planning to switch to a stainless prop, and from what I've heard, I may try out one higher (21) and see if I can maintain my target of 5200. (5250 is the max recommended on my motor)
I found a website the other night that had calculators for what you "should" be able to get. What is the gear ratio on your FICHT? My merc is 2.07:1. I can't find it again now, but I found a different one.

www.rbbi.com/folders/prop/propcalc.htm

put in 5% for slip. That seems a bit low, but that's the figure that makes the number add up to what I was getting, so it appears that the Superhawk is a fairly "fast" hull. I wonder if your motor might be sitting a bit too low, and thus creating some excess drag that robs your RPMs...
I'm gonna get my prop replaced and then take a look at where the c-plate is sitting when I'm planing. I'll let you know what prop I end up with and how it performs for me. (We've got boat and HP in common, so the info should be informative at the least)

[CMunger]

There are two fin type structures on my Merc, not sure how your FICHT is set up. One is the "main" large one directly above the prop, and the other is smaller, a couple inches higher, and doesn't go back like the lower main one. I am assuming (road to ##### is paved with bad assumptions) that the main one is the cavitation plate. What is the higher one, and does that have any bearing on mounting heights?
What has your speed & RPM experience been? I find it curious that you're running a 21, and Jim's looking at possibly having to drop to a 15...

[DanL]

I run a F-115 Yamaha on my 1750 Fishhawk. My motor is mounted one up from the lowest position. I have a 19" pitch Yamaha prop with a top speed of 45 MPH at 5700 RPM's. I dont have any problems with the motor blowing out.
When I ran a 90HP Evinrude on this boat I tried raising the motor one notch to gain speed. When I did this I did have problems with the motor blwing out on turns and rough water.

[gunnar]

Yes the big one is the cavitation plate. With optimum trim I'm running at 5200rpm, the redline on this motor is 6000rpm. Heard or read somewhere that going down in pitch can not only increase rpms but also reduce or eliminate cavitation. My speed with this rig is up to 45mph gps. Guess I should try a 19 pitch and see what happens.

[JimmerAB]

Hi Gunnar,

I think the 1750 Fishhawk and the 1700 Superhawk are very compareable with respect to weight, beam, etc. A 21-pitch seems like an awful lot of prop for our 115's. I'm very curious...what speed and WOT rpm's are you able to get with your setup?

Where in Canada are you traveling to? Wherever it might be, I hope you have a super trip with great fishing, and get to enjoy some of our Canadian hospitality. Good luck, and keep in touch!

Jim

[Oops...!]

Sorry Gunnar...I should read closer before posting. You already answered my speed/rpm questions! Take care.

Jim

[JimmerAB]

Hi CMunger,

Thanks for the website info. I entered my info (my gear ratio is 2.00:1 on the Ficht) and it still seems like I'm not getting the performance I think I should. I still am speculating that the rpm's would benefit by lifting the motor, due to less drag. My c-plate looks to be about level, if not a little bit below, the bottom of the hull.

I really like the boat/motor combo so far. Once I get the performance dialed in properly, I'm sure the rig will be everything I expected it to be! Take care, and keep in touch.

Jim

[REW]

Raise the motor to the third hole up.
Install a Raker - stainless steel 20 pitch prop and you will fly.

Take care
REW

The Raker - with its high rake angle -- will have excellent hook up, lift the bow, and prevent blow out.

I would imagine that your RPM's will be at or near the 5000 RPM, and I would expect that your speed will be in the 42-44 mph.

Take care
REW

[Woody]

I'm running a 1999 Yammie F100 on a 1750 Fishhawk. My prop is 12 5/8 X 21. That's what the dealer set it up with when I bought it. I'm currently running 41MPH on the GPS and turning 5800 RPMs. Red line on the motor is 6G. I'm not sure what hole the motor is mounted in, but I think it's the middle one. Reading the replies above, I'm surprised I'm getting the RPMs out of this motor considering the pitch I'm running.

I've been thinking of moving to a 23 pitch stainless prop. I'd love to lower my RPMs down to the 5500 - 5600 range.

No advice here, but hopefully there's additional info for you to consider.