WOT from 4000 to 4400

[bobhol]

I have a 2001 Chaparral 180 with a 3.0 litre mercruiser alpha 1 gen 2 . When I bought the boat last fall I changed the impeller and thermostat (160). The prop on it was a 14by 21 and WOT was 4000 rpm .I changed it to a 19 pitch and gained 400 rpm so WOT is now 4400. Should I try to get more from it by going to a 17 or is it running free enough at 4400 .I rarely run that fast but want to make sure I am not lugging my motor.? second question. My temperature is running up to 185 on the gauge and then always falls back to 170 and starts over .Is that too hot in freshwater? regards,bob

 

[Howard Sterndrive]

Re: WOT from 4000 to 4400

4400 is perfect

My temperature is running up to 185 on the gauge and then always falls back to 170 and starts over

I might try another thermostat if it didn't do that before. The new one might be sticky.

 

[bobhol]

Re: WOT from 4000 to 4400

The old thermostat actually went up to 200 a few times ...thats why I changed it...Bob

 

[a70eliminator]

Re: WOT from 4000 to 4400

My 20' chap. with a 14x21 could get up to 50mph, too fast for comfort in the little inland lakes I use, I switched to a 14x18 ss prop wanting to trade off speed for power. I much rather have the boat jump up on plane fully loaded pulling a tube then go 50mph. I think it's ok to be a little underpropped than over. I don't know how much RPM that little 3.0 is even capable of, probably not much over 4500 limited by intake and cam?

 

[nitrosteve]

Re: WOT from 4000 to 4400

Make sure you check your belt that runs the water pump. When mine gets loose it will heat up at WOT but cool back off at slower speeds.

I am curious as to what speeds your getting with the 19 pitch? I have one on a shelf but I always have so many people in the boat I cant justify using it yet.

 

[89mercruiser]

Re: WOT from 4000 to 4400

I have a 2001 Chaparral 180 with a 3.0 litre mercruiser alpha 1 gen 2 . When I bought the boat last fall I changed the impeller and thermostat (160). The prop on it was a 14by 21 and WOT was 4000 rpm .I changed it to a 19 pitch and gained 400 rpm so WOT is now 4400. Should I try to get more from it by going to a 17 or is it running free enough at 4400 .I rarely run that fast but want to make sure I am not lugging my motor.? second question. My temperature is running up to 185 on the gauge and then always falls back to 170 and starts over .Is that too hot in freshwater? regards,bob

I'd go to a 17 with that 3.0. We just got ours back. Our boat is an 1989 Arrowglass 17ft with 3.0 and alpha 1 gen 1 drive. From my experinece and hr ago, 17 is a good prop to run on your boat as it's similar in size to ours.

 

[fat fanny]

Re: WOT from 4000 to 4400

@ 4400 rpm your right below the service manuals low end range for rpms on a 3.0 don't push it. And as for the stat buy a higher quality stat and you should recieve the range instead of the fluxuation in temp if not I would keep a real close eye on that temp gauge!!!!

 

[bobhol]

Re: WOT from 4000 to 4400

Thanks for all the responses...I can get to 41 mph by my speedo with the 19 prop...I also have smart tabs on and love the steering and am on plane sooner,possibly it may have affected my top speed....the thermostat I purchased was a mercruiser oem part and I will check on that belt for the water pump ...I am thinking of going to a 17 prop 4 blade if I can sell my 21,right now it is my spare...thanks again ,Bob