Not reaching max RPM w/ Yamaha 250 HPDI

[cmack]

I have a Ranger Z-21, its propped w/ a 23M. I live in Colorado so we need smaller props. Anyway, went to Powell over the weeken, I can only hit 5400-5500 RPM and 61 mph GPS. Same boat same motor w/ a 26p hit 71. When I was in Teaxas earlier this year I hit the same RPM with a 25M and 65mph GPS. Been told it could be the VST filter, called the tech and they would love for me to come in a spend $400 to replace everything. Any ideas?

[gf]

cmack - 4/29/2008 12:15 PM

...I can only hit 5400-5500 RPM...

5500 RPM is the MAX RPM for the 250 HPDI, I'm not sure I understand your question.

[cmack]

I should be able to hit 5700-5800 RPM on my VMAX. Yes you are correct about the specs, however, I cannot physically get the RPM past 5500 RPM at WOT. When the same year and model boat with the same engine can hit 71MPH and I am stuck at 61, I don't understand what the restriction is. I really find it hard to beleive that I need to drop my prop down to a 21. I have heard it could be the VST filter, I am just not sure what is going on.

[ken2]

I'd look at the engine height of that other boat, as well as what prop he is running.
Not just 26 pitch, what brand/style prop was it.
Also, what load is he running. Are you loaded heavier?

[cmack]

Did not get the brand of Prop but I did look and our Jackplates where the same and we were both loaded out tournament and fuel load. In Texas I found the sweet spot with my 25M prop, again, could not get past 5500 RPM but my speed increased to 65. If I was thinking I would have slapped my 23M on to see what if any changes there were, I was not thinking of course..... Too busy catching hogs and drinking tequila! Anyway, I had it plugged into a computer and everything checks out fine. If its a filter, which one, do I or should I incure that expense for an exploratory procedure? Could it be the prop? At least it is physically preventing me from blowing up my motor but can a guy have a choice to blow it up or not?

[Mat_HT]

according to my prop calculator, 61 is about right with that prop and that RPM on that engine....and 71 is about right with the other guys 26 pitch - possibly turning a few more rpm's. So unless the motor is not running right - missing or sputtering or something like that, I wouldn't think the VST filter would be clogged. You may just have to play with your motor height and watch your water pressure, maybe you'll be able to get some more rpms out of it. By the way, the rev limiter on your motor is 6150 - not 5500.
Good Luck!

[honkers89]

You should not complain, I have the same motor and I am on my third powerhead. I am trading it for a Yam f150, cant wait to get that POS of my transom.

[SIM]

cmack - 4/29/2008 11:15 AM I have a Ranger Z-21, its propped w/ a 23M. I live in Colorado so we need smaller props. Anyway, went to Powell over the weeken, I can only hit 5400-5500 RPM and 61 mph GPS. Same boat same motor w/ a 26p hit 71. When I was in Teaxas earlier this year I hit the same RPM with a 25M and 65mph GPS. Been told it could be the VST filter, called the tech and they would love for me to come in a spend $400 to replace everything. Any ideas?

Lake Powell is at 3700 feet. So he hit 71 with a 26p and you can only hit 61 with a 23?

You could run it with YDS(Yamaha diagnostic software)and see if it maintains the correct high fuel pressure at WOT....... or see if it drops off. If it maintainsthe spec for the HP fuel readings,then I would assume that it is getting enough fuel.

Andy

[abbie]

check compression

[DEERHUNTER]

WERE YOU REACHING PRIOR TO NOW OR IS IT A PROBLEM THAT HAS JUST STARTED?