88 Merc 260 w/245 cruiser prop question

[BuzzM]

What is the recommended prop pitch (alum)for a<br />Sunrunner 245 cruiser( similar to a Bayliner )245 w/ Merc 260 at about 5800 lbs? A prop shop recommended a 15 1/4 X 15 and it is over revving to 5700 rp.m.s. I am thinking a 19 or 21 would be better.<br />Also, what is a normal oil pressure at idle? I am worried that I may have damaged the engine at those high r.p.m.s. The pressure is about 20 p.s.1. at idle and 30 - 45 at speed.<br />thx for the assist

 

[fendersfender]

Re: 88 Merc 260 w/245 cruiser prop question

i'd try a 19 and oil pressure is ok

 

[MSmith3615]

Re: 88 Merc 260 w/245 cruiser prop question

I'm pretty sure you have the right diam, I believe its 300-400rpm less at 17, 700-800 at 19 and 1100-1200 at 21. Find you WOT range which I believe is 4200-4600 on a 260. I'm not too sure on your WOT, it should say on the motor what your WOT range is. Find it then go from there and remember every time you go up 1 its equal to a decrease of 200rpm and when going down in pitch rpm increase 200rpm for 1. As far as oil pressure I'm not sure, I've got a 87-260 and mine is in that range. I will say 5700rpms is way too high. At least it is for my motor.

 

[MSmith3615]

Re: 88 Merc 260 w/245 cruiser prop question

A 2" increase in pitch usually decreases RPM's 300-400rpms. Find WOT and see how much higher you need to go.