1984 Bayliner ciera 2750

[Sharkbaite]

I have a '84 Bayliner 2750 Ciera and I am curious as to the Prop size, and the RPM's needed to run the boat. I recently had my prop repitched to 21 degrees as my RPMs in my opinion were to high, but after talking to another boater he stated he runs his bayliner above 4400 RPM.

What I would like to know for this size boat, what is the average cruising speed vs RPM. I have a AQ260 350 V8, with a 280 drive. I am currently comparing it to my older boat I had, where as I don't like to run it above 3400 RPM, am I wrong or should I up the RPM's and let her run that high??? any input to the specs or if anyone has a copy of the "{owners" manual??? LOL

I have read through some of the stickies, and I found a couple post about running the boat in the low to mid 4000 range, but I have Never ran an engine that hard except in my car when racing LOL

Ideas???

 

[Maclin]

Re: 1984 Bayliner ciera 2750

You need to have a prop pitch that will let your AQ260A engine rev up to 4400-4600 at WOT. If you put too high of a pitch prop on and the top rpm's are 4000rpm or lower then you risk lugging the engine even at the lower rpm's causing premature failure like tuliped valves or extreme detonation burning up pistons or even dropping a valve.

A 21p may be ok, but for a 27 footer single engine I would think a 19p is closer to optimum.

You need to make sure the engine is in good tune, and obtain the top RPM you can reach at WOT (Wide Open Throttle), and an accurate speed at that rpm. With numbers like that a proper pitch can be determined.

 

[steelespike]

Re: 1984 Bayliner ciera 2750

Basically the motor needs to be able to rev freely within it's rated wot rpm rating.You can operate it at whatever rpm you favor.
Maclin's 19" pitch suggestion seems reasonable.

 

[Sharkbaite]

Re: 1984 Bayliner ciera 2750

Well looks as though I will need to go find another prop at a 19 pitch and put back on, I will also need to change my thermostat to a lower rated one, as the engine runs warm it I run over 4000, I may have the wrong thermostat. I think I have a 190 in it, and thats 50 degrees to hot according to the specs in my book. During the winter that thermo was good, but now that the water has warmed up, its allowing the engine to run warmer than I like....Great another trip to the store.... LOL

Thanks for the info, I didn't know I could run it at those RPMs without damage to the engine...

 

[Maclin]

Re: 1984 Bayliner ciera 2750

I would recommend you spring for the Volvo Penta thermostat kit for your engine. The price may seem high in automotive terms but the correct materials and heat range and quality are in there, makes a big difference in longevity. both for the thermostat and the engine.

Do you have the owner's manual for the AQ260A? If not you can take this link, type in AQ260 in "Engine type" then click "Search >" and a list of downloadable documents will be shown...:
http://www.volvopenta.com/VOLVOPENT...LICATION_SEARCH/Pages/publication_search.aspx


While Volvo Penta recommends, for a sustained cruise speed, being 300-400 rpm below the top rpm your engine can achieve, they assume that your engine can achieve a top rpm in their specified range. For the AQ260A I believe the range is 4000-4400. So they are saying don't run it at 4400 for very long, but the engine can run at 4000-4100 for long periods.

 

[Maclin]

Re: 1984 Bayliner ciera 2750

Shark, note that I have the top rpm range wrong for the AQ260A in my first post. I believe what I have in my second post is more correct at 4000-4400.