Prop size?

[Micheal J]

OK,I've been reading alot about props and props sizes,and the more I read the more confused I become.
I normally run w/dive gear for 2 dives for 2 divers,and sometimes w/the bait tank full,so its gotta be on the heavy side w/ always a full tank of gas. I normally turn about 4200-4400 rpms,and that puts me at 23-27mph depending on sea state.I'm real anal about watching my temp,cause I putt around kelp to get to my dive sites,so when I'm running 4200-4400 and not around the kelp my temp stays about a little under 3/4 bars on the gauge,but when I run it any higher than 4400 rpms the temp goes up on the gauge over 3/4,but a little under what I would call running hot.Is this normal running temp? Loaded with what I've decribed, WOT only turns 5300rpms on glass water,but I am hauling a&* doing about 37mph.I guess what I want to know is should I be running the boat at 4200-4400 and keeping the temp down or running a little faster and keep the temp up?
The normal sea state around my parts really wont let me run it uphill at those rpms without a beating,but I normally can running downhill.
So am I running this motor too cold,without enough rpms, should I try a different prop?Id like to go stainless cause it cuts the kelp eaiser. The motor I have is a 07 Yammi F200.
Any thoughts on prop sizes or any other feedback would be helpful.
Thanks MJ.

 

[Robert Cibran]

that motor should be able to do 6,000 RPM at WOT with 2 people on boat no gear 3/4 fuel,once you load her up,you will loose some RPM'S.

I do not think that you would loose so much as to be 5300 at WOT,you probably should be at around 5700 to 5900 loaded.

Robert

 

[TheOtherLine]

I guess what I want to know is should I be running the boat at 4200-4400 and keeping the temp down or running a little faster and keep the temp up?

I am not a mechanic and don't run in waters that have kelp (which you assuming is what is causing the engine to run hot ). Having said that, I just can't imagine that those are your only two choices (slow or hot).

It's going to be interesting to see what kind of solutions CP members come up with but, If I were you, I would contact Yamaha and see if your problem with running hot, is in fact, a kelp issue.

I guess if the kelp is "fouling" your prop or intakes, then it would make sense. On my 2520 with a Yami 250, 4200-4400 IS the sweet spot.

 

[Micheal J]

Thanks for the input guys,may be I should make myself a little more clear.
I just putt through the kelp at about 1000 rpms max,and there was one time when I got an alarm and the motor shut down.Sure enough there was kelp stuck in one of the intakes.pulled it out ,started it up,and it cooled right down no problem.
I'm just wondering if I'm luggin it at 4100-4400 cause it doesn't get the temp up to 3/4 on the gauge.It does seem to be the sweet spot for the boat going uphill or downhill.
If the motors supposed to turn6000 do you guys think it's a prop issue,or a big fat diver guy w/alot of gear,and gas? Also still looking for suggestions on stainless prop sizes for my probable issuses even if there are any. Also the best mpg I get is 2.5,and thats when it's glass,and that doesn't happen around here very much.
Any help would be awesome
Thanks again.
MJ.

 

[BradV]

i would imagine the reason your motor is overheating is that you arent propped where you turn 6000 rpms. even if you are super loaded and that means double what your limit of weight is you still wouldnt lose 2000 rpm. What size prop are you running? i would imagine with the 200 you should be able to run a 17 pitch on that boat.

 

[TheOtherLine]

have you checked out this sticky?

http://classicparker.com/phpBB2/viewtopic.php?t=2595

 

[Micheal J]

Thanks guys,I'm still looking into it.
It's obvious to me I have alot to learn about props in general,and this motor. I'll talk to my machanic,and next time I'm out I'll get some info ,and post it up.Still looking for info on stainless prop sizes for my application.
Thanks again,and Happy Thanksgiving to all.

MJ.

 

[Megabyte]

The heat issue really shouldn't have any bearing on engine RPM, so I would take a look at my water pump first.
If kelp has gotten sucked into the pump or the water passages, that might account for the temperature issues.
Have you ever given your motor a Salt Away treatment?

 

[Micheal J]

Yes,I always give it a Salt Away treatment after 15 mins of flushing.
So if I understand you right,when I'm running at anything below 4400 rpms,and the engine runs at a little under3/4 on the temp gauge.Then I run it above 4400rpms,and the temp goes up above 3/4 this is not normal? Are you saying that the higher rpms should'nt have any thing to do w/the rise in temp?

At the first 100 hr sevice the mechanic told be I didn't have to replace the water pump.I told him to replace it anyway cause I knew i was going to put alot of hours on it in a big hurry because of lobster season.
So he replaces it and shows me a partially melted houseing,and asks me if I ever ran it on earmuffs.I told him I have never run it on the muff ,just the flushing attachment.
Now ya really got me thinkin.
Still.. Thanks for the info.
MJ.

 

[captbone]

You run it on the flushing attachment?

No water gets to the waterpump if you run the engine with the hose hooked up to the flushing attachment hose at the powerhead.

You should never run the engine without ear muff or the lower unit in water or you will melt the waterpump.

 

[Micheal J]

You run it on the flushing attachment?

No water gets to the waterpump if you run the engine with the hose hooked up to the flushing attachment hose at the powerhead.

You should never run the engine without ear muff or the lower unit in water or you will melt the waterpump.

I don't run the motor at all,just flushing thru the flushing attachment,then a Salt Away treatment.
I know Yamaha reccomends just fushing thru the attachment,so thats what I do.
Yes I am aware of the waterpump pickup on this motor,and thanks for your comments,it's always a good idea to give folks a heads up,cause you might know something that they are not aware of.
Thanks again,I'sooo glad I ran across this site. 8)
MJ.

 

[Megabyte]

When the water pump was replaced by the mechanic, do you know if the thermostats and poppits were replaced?

 

[Micheal J]

No Mega bite I dont,that seems like a VERY valid question.Do you know if that would be covered under warrenty right now.I took delivery of this boat in April 08,and right now it's coming up on about 180hrs,I might just bring it in a little early to get this issue taken care of.
Like I've stated it doesnot run up to 3/4 on the gauge at 4400 rpms. anything over 4400,and it will run hotter,over 3/4 on the gauge,but not enought to shut the motor down.Should the temp be at a little under 3/4 at any rpms?

I know in my old 2003 Evinrude 200 hp 2 stroke this was a sign of that it was time to replace the waterpump. I dont know but when I talk to some Tech's about this I get some different answers,

Thanks again guys for all your help.
MJ

 

[Megabyte]

If the motor is still under warranty, I would definitely have a certified Yamaha mechanic check it out.

My motor is a 225 OX66 and the temp does not vary according to engine speed. I would think that it would be the same for the 4-stroke motors, but the mechanic would be the best person to answer that question.