2 stroke question

[Sea Ranger]

When I bought my boat(new to me) I was told to punch it hard and quick when taking the boat onto a plane. I thought it was easier for the engine if you bring your rpms up slowly and go onto a plane slowly. My 2 stroke is a 90 hp. How hard do you punch it when going onto a plane? I was also wondering what the max rpms would be for a 90 hp 2 stroke. Wide open my rpms are around 4400 but I don't normally run it above 4000 rpms. I don't know a lot about outboards as you can probably tell.... Steve.

And remember....Keep your tip up!!!

 

[Island Fish Lifter]

Steve, You should be getting 5800 rpm at WOT. You either need to decrease your prop size and/or pitch. If you continue running it like that, youll decrease the lifespan as it is overloaded all the time.
There is a possibility that it may not be developing full power. So, before spending $ on props, do a compression test and make sure all cylinders are firing.
What size of boat is the 90 on and what size is your prop now? An 18' boat with a 90hp 2- stk. should have 14 x 17, to 14x19 in aluminum (the last number represents the pitch), stainless size will need to be 1" of pitch less.
Punching the throttle wont hurt it, that is if your transom is good.

Fill the dam tub!

 

[cedarman]

Hey Steve another idea which you could look into is see the condition of your throttle cable. Mine on my old 90 hp got stretched and would not reach WOT. I was fishing in Bamfield for the weekend and had to run it and by the end of the weekend it would not excelerate with any kind of get up and go. Cheap fix only around $500 if you hire someone to fix it but it is a do it yourself project. hope this helps.

cheers

 

[Sea Ranger]

quote:Originally posted by Island Fish Lifter

Steve, You should be getting 5800 rpm at WOT. You either need to decrease your prop size and/or pitch. If you continue running it like that, youll decrease the lifespan as it is overloaded all the time.
There is a possibility that it may not be developing full power. So, before spending $ on props, do a compression test and make sure all cylinders are firing.
What size of boat is the 90 on and what size is your prop now? An 18' boat with a 90hp 2- stk. should have 14 x 17, to 14x19 in aluminum (the last number represents the pitch), stainless size will need to be 1" of pitch less.
Punching the throttle wont hurt it, that is if your transom is good.

Fill the dam tub!

Holy crap fish lifter, I had no idea I was putting my motor under a load like you said. It runs fine and doesn't sound like its crapping out so I'm sure its running on all cylinders. My boat is a 17 foot Arima, not a big boat but not a light boat either.

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I just assumed that the prop and motor were propperly matched.
Will I find a number on the prop somewhere that will tell me the pitch?


Cedarman.... The throttle cable runs smooth as well so I don't think thats the problem either, The motor will rev out more but I was keeping the revs down as I thought I was doing my motor a favor.... ARGGGGG!!!


And remember....Keep your tip up!!!

 

[nedarb2]

if you take the prop off it should be written on the back of the hub - see below picture.

Try this out and see what it says also:
http://appcenter.mercurymarine.com/propSelector/home.do

Just for your information, im turning 14x19'' on my 200hp - for a 90hp it should be much less

 

[Sea Ranger]

Thanks nedarb2,
I will check this weekend and see what prop I have.

And remember....Keep your tip up!!!

 

[Sea Ranger]

Does every one run their 2 strokes in the 5000 rpms and more?

And remember....Keep your tip up!!!

 

[nedarb2]

quote:Originally posted by Sea Ranger

Does every one run their 2 strokes in the 5000 rpms and more?

And remember....Keep your tip up!!!

Your welcome
you dont run them in the 5000 rpms, you still cruise at 4000rpms or w/e your cruising speed is, but you have to be able to attain the 5800rpm becasue that shows your prop is the right size for your engine as fish lifter said. If you cant reach that rpm, it means your engine is working to hard to attain the rpm's that it is able to get to. Think of it as being geared to high, you can always go up a hill, but your engine is working way to hard to do it.
Even if you cruise at 4000rpm, your engine is working like your at 90% throttle instead of 60 or 70%.


i just did some research online and someone with a simialr boat as yours and a 90 honda is running a 13.25x17 prop and getting 5800rpm

 

[Island Fish Lifter]

No, not unless they own a gas company. Max rpms is the way to select a correct prop. Your boat and motor will just feel and sound right when you find the best speed for your boat.

Fill the dam tub!

 

[scott craven]

You should be getting at least 5500 rpms at WOT.
It would seem the prop is pitched wrong, and that is why
you're not getting good "hole shot"
engine is working too hard to spin the prop.

 

[Island Fish Lifter]

sorry nedarb, we must have posted at the same time.

Fill the dam tub!

 

[profisher]

For longer engine life I always prefer the engine to over rev slightly over manufacturers maximum rpm's. Just don't take it up over the maximum rpms. By matching a prop that gives you this scenario you will be running at cruise speed in a lower gear and taking strain off the crank and rods. Your hole shot will also be quicker and again less strain on the engine. My 200 2 stroke should top out at 5400-5500 if matched to factory specs. I'll pick a prop that will allow 5800 rpms. JUST DON"T GO PAST 5500 RPMS!

 

[Sea Ranger]

Thanks guys, I didn't even know I had a problem. I will look into this a lot more and figure out what prop I need. So, do I want to put on a prop with less pitch and that will increase my rpms? How do I know which pitch is best.... Trial and error???

And remember....Keep your tip up!!!

 

[Sea Ranger]

Thanks guys, I didn't even know I had a problem. I will look into this a lot more and figure out what prop I need. So, do I want to put on a prop with less pitch and that will increase my rpms? How do I know which pitch is best.... Trial and error???

And remember....Keep your tip up!!!

 

[scott craven]

Can you advise diameter and pitch of current prop?
should be stamped on the hub or possibly on one of the blades...

 

[scott craven]

Can you advise diameter and pitch of current prop?
should be stamped on the hub or possibly on one of the blades...

 

[Island Fish Lifter]

i just did some research online and someone with a simialr boat as yours and a 90 honda is running a 13.25x17 prop and getting 5800rpm
[/quote]

This is probably a good place to start. Most prop shops will let you try a few different ones until you get it right.

Fill the dam tub!

 

[Island Fish Lifter]

i just did some research online and someone with a simialr boat as yours and a 90 honda is running a 13.25x17 prop and getting 5800rpm
[/quote]

This is probably a good place to start. Most prop shops will let you try a few different ones until you get it right.

Fill the dam tub!

 

[Fish Assassin]

Where are you located Sea Ranger? What make of motor.

It would take no time to check linkage, prop size and compresion. Glady help if your near by.

Hey that is an Arima. Have you put it on a scale. I ask because I thought for a period of time they had a foam problem. The foam would hold water if it got in. The weight would cause the problem as well.

 

[Fish Assassin]

Where are you located Sea Ranger? What make of motor.

It would take no time to check linkage, prop size and compresion. Glady help if your near by.

Hey that is an Arima. Have you put it on a scale. I ask because I thought for a period of time they had a foam problem. The foam would hold water if it got in. The weight would cause the problem as well.