yammie 3600 rpm to little or not enough

[Vallejojoe]

I just bought a 20' alum. boat with a gil bracket it has a 200 HPDI yammie an it runs at a perfect speed and sound at around 3600 RPM.will this be harmfull to the engine? don't get me wrong it is also fun to run it at full throttle. Also what kind of tubing do you use to hook up a water pressure gauge made by Yamaha? Thanks Much :

 

[hondon]

Re: yammie 3600 rpm to little or not enough

The real criteria is gathered at wide open throttle where these things have been engineered to run.You should turn a specified amount of RPMs at wide open within a specified range.If those RPMs are too low you are lugging that engine in likely all RPM ranges. Too high and you risk overrev damage or continual activation of the rev limiter at wide open.If you are propped right running in your comfort zone should not cause you any problems but it would'nt hurt to open her up up from time to time.

 

[Vallejojoe]

Re: yammie 3600 rpm to little or not enough

Thanks for your input the engine runs about 5100 rpm wot full tank of gas and two adults and fishing gear, motor onlt has about 15 hours on it should I reprop it for a few more rpm? RPM red line is 5500

 

[Pursuit2150]

Re: yammie 3600 rpm to little or not enough

Don't worry about "Red-Line" , you don't want to run it there too long anyway. With an engine that new, you should not run it too long at any RPM , vary the throttle, till you get some hours on the engine. I normally run at crusing(Plane) speed, most of the time, and really punch it when coming home, for about 3-5 minuits, cleans out the engine. Don't even worry about a re-prop, 5.1K is fine.<br />I guess I don't understand, why a lot of people want to go to "RED-Line.What's the point? BLOW THE ENgine, Or Brag Rights?

 

[evin300]

Re: yammie 3600 rpm to little or not enough

pursuit2150, What dont you understand about running a 2-stroke at the proper RPM range? <br /><br />You dont put your car in 4th gear and gas it before you climb a hill do you?<br /><br />If you want to compare a car to a boat (bad idea) your car would be climbing a hill CONSTANTLY to equal the load placed on a marine engine, buy running at and below the recomended range, you risk excessive loading and create lots of carbon.<br /><br />I hate to say it, but the only one thats gonna blow his engine, is you.<br /><br />In this case, 5100 RPM is the lower end of the range. I would prop the boat for how you normally use it, 2-adults etc. Then try for 5300-5500 with this "normal" load in the boat.<br /><br />Sure, you may go to 5600 or 5700 with a very light load, and 4900 to 5100 with a very heavy load, but this wont be the "norm". <br /><br />Dont get too excited about this red-line stuff, Its more for determining where your engine makes peak horsepower, find out what your rev-limiter setting is, and stay away from it, this, in my opinion is the true red-line.<br /><br />Remember, with a propeller, you only have one gear, you just cant downshift, and climb that hill. Since you only have one gear, you have to make the best of it.

 

[Fouled Plug]

Re: yammie 3600 rpm to little or not enough

Vallejojoe, you may want to drop pitch by an inch or two if that is your typical load. 2 strokes really hate to be lugged, and even if you rarely punch it to WOT you want it propped to the correct RPM's when you do. Top end RPM's have very little to do with "hot rod" mentality, and very much in common with long engine life. The prop should really be your "rev limiter", peaking nearer your WOT recommendations.

 

[steve forsythe]

Re: yammie 3600 rpm to little or not enough

What is the best rpm's to cruise??? When coming in or going out, assuming good seas, where should i level her off? WOT is about 5500-5800. (200hp Merc Carb) I just assumed you did not want it 'floored' or 'punched' for long periods of time. If i am on flat seas i might be running her for an hour straight or more. Stay a little below WOT - 5000????? Thanks.

 

[SeaDawg]

Re: yammie 3600 rpm to little or not enough

I've never heard of anyone blowing an engine from running it "wide open", as long as the engine was not running over the maximum recommended RPMs in the manual.<br /><br />Sooooo, you could run it flat out for an hour and be OK. HOWEVER, you will gulp the fuel. Look at the fuel curves for any engine, and they drastically increase as you near WOT.<br /><br />My current motor max. recommended rpm is 6000 (and the prop will let it barely hit it if I want to), so I'll probably "fast cruise" in the 5500 rpm range. Not because I'm worried about blowing the engine, but I want to use about 10% to 20% less fuel.

 

[Hawkeye1]

Re: yammie 3600 rpm to little or not enough

Ok what rpm to cruise at. I put 1600 hrs on a 200 yamaha and sold it 2 years ago and it still running like a top. I had it proped to turn 5500 with a normal load and use to cruise at 44 to 4600 for hrs at a time. That is where i got the best MPG on my rig. I told the to the guy that bought it and he runs it the same way. Engine still purring strong over 2000 hrs. Compression was within 2 lbs on each cylinder at 1600 hrs as it was at 600. I ran ring free and atleast mid grade fuel. Decarbed it every year or about 300 hrs. The responces above are correct that 2 stroke live longest when they are not lugged by overproping. Giving you are in your recomended rpm range but i would go down 2" more in pitch the give that horse some breathing room. She will come out the hole much better and carry a load better at slower speed also.

 

[steve forsythe]

Re: yammie 3600 rpm to little or not enough

Ok, i am confused. I think my optimum rpms at WOT is 5600-5800. If anyone knows different...please tell me. (200hp Merc carb) I would love to get up on plane faster...cruise at 4500 rpm's with good fuel economy....and carry heavy loads (3 people, ice, coolers, gear etc.)I dont care too much about top speed ...but i dont want it to be a slug either. She tops out at about 35-37 knots now, which doesnt feel that fast. It has a stainless 17" now. Not sure of the pitch. I also noticed that with following seas or if you trim up the engine a hare she can approach 6000 rpm's. Is this bad? Anyway...what advice do you all have for my situation?

 

[SeaDawg]

Re: yammie 3600 rpm to little or not enough

PS, it looks like you are propped about right for your boat. Meaning, you are hitting your max. recommended RPMs with WOT and normal load.<br /><br />It must be a big one, if you have a 17" pitch prop on it now.<br /><br />Yea, if you are trimmed too high or the motor is coming out of the water, it will overrev.<br /><br />Sorry, the only way to get more speed is a bigger motor.<br /><br />Read some of the other posts on hydrofoil fins and trim tabs. They will help you get on plane quicker, but may hold your boat nose down too much for your feeling of safety (especially in the ocean).<br /><br />Hope this helps.

 

[Hawkeye1]

Re: yammie 3600 rpm to little or not enough

PS I was recomending to the origanal poster to go down 2" of pitch cause he is at 5100. You on the other are right where you need to be. Not much else you can do as seadawg stated. It get confusing figuring out you to answer in these post. I work 3rd shift and was busy as heck last night when I was replying.

 

[Vallejojoe]

Re: yammie 3600 rpm to little or not enough

Thanks so much for all your input this is my first outboard I had a 350 in my old wellcraft.You guys are telling me to prop down a little, right now it is a 13 3/4 x 21 so should I go 19 pitch and what will more dia. do for me?

 

[Hawkeye1]

Re: yammie 3600 rpm to little or not enough

Dia might not do much. It will depend on how the mfg measures the pitch and rake. A 19 of what ever prop your running now will get you up to 5500. Now you might not gain any top speed and in some cases loose a 1 or 2 mph but the boat will come out the hole and carry a load much better.

 

[steve forsythe]

Re: yammie 3600 rpm to little or not enough

SeaDawg...what parts of Delaware are you from??? I grew up there....north Delaware, 18 years in Hockessin.