Suzuki DT115 RPM's

K

Knightgang

Lieutenant
Joined
Oct 6, 2003
Messages
1,428
I have a 1985 Suzuki DT115 on an 18' Cobia Sunskiff SS200 Center Console. The hull is a deep V and lightweight. According to NADA specs, the hull only weighs 1000 lbs. I have a 36 gallon gas tank, so I figure my weight to be as follows:<br /><br />Hull 1000<br />Motor 400<br />Gas 210<br />Misc 100<br />Total 1710 appr<br /><br />Now, I am not sure what size my prop is (I will look this weekend) but with my 230 lb rear-end at the helm and another average passenger, she turns about 6100 RPM and tops out at about 39 MPH. I am thinking that I should change out my prop to reduce a couple hundred RPMs and get a few more top end MPH.<br /><br />Am I thinking right? What RPM range should I be running in? I just want to be sure that I am running my engine at its most effiecent performance and not doing anything to cause an untimely failure.<br /><br />Thanks all.<br />Knightgang
 
M

mrn714

Petty Officer 2nd Class
Joined
Aug 15, 2003
Messages
178
Re: Suzuki DT115 RPM's

Based on my past experance with the DT motors under 200 hp, prop choice is not that big of a deal. Your <br />weight calculations seem a little low. I would add another 500 for the stearing, throttle, wiring, lights, and possible water gain in the hull due to age. When I put my hull on a truck scale, it was 700 lbs over the quoted for the type. As for the ROPM, sound high, are you sure the guage is OK? IN some cases, the guage will be bad and show higher. You speed with the HP seems OK. Are you trying to make it a racer? If so, more HP would do more than a prop change. With the props available I am not sure you would de 5mph better, and with the cost of the prop the increase may not be worth the price. <br /><br /> :rolleyes:
 
K

Knightgang

Lieutenant
Joined
Oct 6, 2003
Messages
1,428
Re: Suzuki DT115 RPM's

No, not trying to make a racer. I do plan on offshore fishing out to about 15 miles.<br /><br />I want to be sure that I am getting the efficency that I should from the engine and as much speed as it can REASONABLY put out.<br /><br />I have been reading alot on here and most comments are to look for about 5500 to 5800 RPM and I figured mine was a little high. It has the original Suzuki Tach. Did not work when I first got the boat, now seems to work fine. I assume it is right. I plan on building a new console this summer and outfit it with new gauges. I am thinking of Teleflex Gauges but don't know yet.<br /><br />THanks<br />Knightgang
 
LubeDude

LubeDude

Admiral
Joined
Oct 8, 2003
Messages
6,945
Re: Suzuki DT115 RPM's

Its always nice to have your engine set up for max speed incase you have to make a run for it, but you will find your fuel consumption will be best at about 2/3 throtle! Close to half!!
 
K

Knightgang

Lieutenant
Joined
Oct 6, 2003
Messages
1,428
Re: Suzuki DT115 RPM's

Okay, I checked my prop today, but there are no numbers stamped on it anywhere. I checked all around the hub and on each blade. Nothing.<br /><br />I have another prop that came with the boat as a spare. I have not looked for numbers on it yet. I guess they are the same but may not be. Next time out, i will put that prop on and see what the RPMs do.<br /><br />What is the optimum RPM for this engine?<br /><br />Thanks
 
J

jim dozier

Lieutenant Commander
Joined
Jan 8, 2003
Messages
1,970
Re: Suzuki DT115 RPM's

Did you remove the prop when you checked for numbers? Mine are stamped on the forward edge of the hub and you have to remove the prop to see them.
 
K

Knightgang

Lieutenant
Joined
Oct 6, 2003
Messages
1,428
Re: Suzuki DT115 RPM's

I need to pull it out to crank it today, I will look and see.
 
K

Knightgang

Lieutenant
Joined
Oct 6, 2003
Messages
1,428
Re: Suzuki DT115 RPM's

Okay, I pulled my prop today to check its size. I also looked at my spare prop. To my surpise, my main prop is a 13X19 Stainless prop. I did not realize it was SS until I noticed the weight difference between it and the spare.<br /><br />My spare prop is a 13X21 aluminum. Is there going to be very much performance difference between these two props? <br /><br />What is the recommended RPM range for this engine?<br /><br />Any ideas what a prop shop might charge to mofidy my SS prop to a 21 pitch?<br /><br />Thanks
 
D

DJ

Guest
Re: Suzuki DT115 RPM's

I had a 1995 DT-140. That is basically the same engine as the DT-115.<br /><br />The dealer set it up to run at 6100-WOT. I believe the rev. limiter kicks in at 6400. The 2-stroke Zuki's like to run fast.<br /><br />As a basic rule, one inch in prop pitch is worth 200 rpm's. (up or down) Take that for what it is worth.
 
K

Knightgang

Lieutenant
Joined
Oct 6, 2003
Messages
1,428
Re: Suzuki DT115 RPM's

As a basic rule, one inch in prop pitch is worth 200 rpm's. (up or down)
Click to expand...
Which way? I assume that more pitch reduces RPM's.<br /><br />In your opinion, should I go with the the aluminum 13x21 prop or stick with the SS 13x19? I have not run the 13x21 yet, but I like the idea of a SS prop. I also want the best overall performance, not neccessarily top end. This boat will be used for everything.<br /><br />Thanks
 
D

DJ

Guest
Re: Suzuki DT115 RPM's

Knightgang,<br /><br />The one inch to 200 rpm rule works both ways. <br /><br />I ran the DT-140 on a 19'Palm Beach Bay Dancer (bay boat). I stuck with the 19", for hole shot, and just watched my WOT rpm.
 
You must log in or register to reply here.
Top