should i be worried?

[starcraft1982]

ok.1988 150 black max.from post on here and one on props section,ive determined i need to step up in pitch on my prop to bring WOT rpms down.this boat is new to me,cajun 18 1/2ft bass boat.at WOT it is up to 6000-6100rpms.changing pitch will bring rpms down between 250-400.so couple questions.1)should i throttle back until i get new prop?is 6000 too much for that motor?2)ive been informed on here that manufactures recommended rpm range is 5000-5600.so even w/prop change i'll still be a little high of that.so,is there an adjustment that can be made to bring rpms down a bit,like set screw or something or is it more involved than that and better left to someone who knows a little more than me!!?thanks to all who reply.i love this motor and really dont want to smoke it!

 

[saumon]

Re: should i be worried?

No set screws or anything like that. Just get a prop wich is 2" more in pitch. That will put it exactly where you want it to be.

 

[alwims]

Re: should i be worried?

Hold on a second. If it's an XR2 it's running about right. If not then fix it. This place is a wealth of info and has helped me immensely over the years, but Don't be so quick to believe everything you read here. As John Martin says, get the manual and read it. Here is what the manual says,

TUNE-UP
Hp/rpm:
Model 135 135/5000-5500
(100.7 kW)
Models 150 & 1500 150/5000-5500
(111.9 kW)
Model 150 XR2 150/5500-6000
(111.9 kW)
Model 150 XR4 150/5000-5500
(111.9 kW)
Models 175 & 1750 175/5300-5800
(130.5 kW)
Models 200 and 2000 200/5300-5800
(149.2 kW)
Model 225 225/5300-5800

 

[j_martin]

Re: should i be worried?

Any of them would rather be over-rev'd a bit than overloaded. A bass boat varies considerably in weight depending on fuel and livewell load.

On some, for instance an XR4, there's an "advance" module that moves the timing from 19 degrees to 23 degrees at 5000 rpm, and then backs it off to 17 degrees at 5500 rpm. Without the timing module, the engine pulls well to just past 6000 rpm, then carburetion, porting, etc. rapidly limit the torque.

I don't think you're hurting your engine, but you might pick up a bit at WOT and give a bit in the hole shot by increasing the prop pitch.

hope it helps
John

 

[Faztbullet]

Re: should i be worried?

If it was me I would leave it alone or add a little cup to prop as this will drop rpm about 150rpm. It wont hurt to turn that engine 6000 as it was the best 2.0 liter block years made but you also have to remember that the water is hotter this time of year thus less dense so prop slippage goes up....