Yamaha 30hp cylinder help

I joined the forum because I want to learn how to go fast. I am still in college and do not have the money to pay someone to work on my motor and to be honest I actually kind of like working on it. Well here is what I have. I want to make my duck boat faster. The place I hunt is limited to 25 hp outboards. Because we have to cross logs, bounce off trees, and run in through stuff everyone runs a welded metal boat. I have a 2013 edge boat. The boat is 15 foot long and 50 inch wide (it actually narrows down a few inches towards the back). The boat weights 320lbs. The motor I am running is a 1987 30hp Yamaha 3 cylinder 2 stroke. I have CMC PT-35 T/T. I am running a 13p PowerTech SS SRA3 prop. With just me this boat runs at 37mph. I would like to make it go faster. I have some ideas of a few mods I can do that will help me out but I was wanting some feed back from people who know what they are talking about. So far my motor is totally stock pull start only motor. Here are the first three mods that I thought might help me. 1. either buy a aftermarket high performance head or have my shaved to boost engine compression. 2. boyesen reeds. 3. take the flywheel somewhere and have it lighten. If I do those three things. how much speed/ power will I gain? Will I have to change the type fuel I run? Who makes a good high compression head? And lastly What mods do you know, that do not cost a fortune, that I could do to gain speed? I would like to gain 6mph+. I don't have a tach, so I have no clue what my rmps are. Thanks in advance.

You are on the right track! CCM reeds, but put them on 40hp yamaha cages. I may have a set. Yes on the flywheel, many shops can do it, I can if you need. you need a set of 40 tohatsu carbs. And on the head mill it to 160psi and run pump gas 87. I just finished up with a 90 today. 150psi, 87 pump gas, 7300- 7400 rpm, pulls like a bull out the hole.

look at hydrotec marine at some of their exhaust tuners and get some bigger carbs. Then she will breathe!

Go to boats.net and order a 30 tuner. Cut tuner down at the water intake. Tohatsu 40 carbs with 122 jets, carbon fiber reeds, port the intake to match bigger carb ventura. I would not up the compression on this motor if you want to keep it reliable and run for a long time. You will need to put the bottom Tohatsu carb in the middle to line up vacuum port for fuel pump.I took a stock 25 Yammy runnin 28MPH on a 1546 Xpress ( heavy boat ) and doen these mods and runnin 36MPH. I still need to work on setup, prop, jack plate etc..You may find some carbs from Alex a APBA M50D builder. 207-737-4570Good luck, Bobby..

Hey 88. Will the Yammy 40 cages fit the 25 intake??

Hey river 37MPH is haulin but with a stock 25....

ive always been underthe impression a lightened flywheel is only for acceleration.
weve never had it for any top end boost,and also found it gives poor idle if you want to idle that is ?

but some good avice above about the mods,



phill

I run the E free 87 in my Merc 25ss and Yamato Y80 on a hydro because it runs better than the higher octane stuff that has many additives and burns slower. Plus these engines are not really high compression 125 psi in the Merc and 150 psi in the yamato.

What is your reason for using the 87 even at 160 psi?

Number 1., get a tach. You don't know what you have or don't have if you don't know engine speed. Tiny tach's are cheap, and you simply can't start evaluating what you have done without it.

Number 2. find out what RPM's you should be running for the porting you have and to get a reliable long life and don't over rev the motor. You don't have a lot of extra money to be rebuilding this thing on a regular basis, so keeping the rpm's in the right range will maximize your speed as well as help the engine live a long time.

Number 3. Get a water pressure gage and a low water pickup and a nose cone. All of these are cheap, help you go faster and don't cause you to abuse the engine.

Number 4. Get the motor as high as you can and still have water pressure and see where you are in terms of rpms and speed.

At this point if you still want some more speed, you can start digging into the motor and start changing props, but if you don't have a lot to spend you can gain a lot of speed for not much money if you look at setup before you start working on the innards of the motor.

yellowjacket is absolutely right, with a tachometer to see how it goes your engine .. if you are at very high rpm range considered to 14pitch or 13.5pitch increase. You can also modify your carburetor giving more air opening and head to 150-160lb maximum, this will give you more power and better will move the propeller with more pitch. but everything you say here is good, it all depends on how much you want to spend. maybe if you change the propeller you save time, everything depends on the RPM