Twin Merc 150's hi RPM & No power

[Gaucho]

Hey all:<br />I am new to boating just bought a 95 Trophy 25' with twin 150 Merc's I was told not to run over 4000 rpm but i seem to get no power at anything less than 3000. Could there be a problem? And i also have to get the rpm up to 4500 then drop it down just to get any speed at all.<br />Any tips please help a newbie out.<br />Thanks

 

[clanton]

Re: Twin Merc 150's hi RPM & No power

After breakin the 150 carb engine should turn 5000 to 5500 at full throttle, from Merc manual. The boat should be propped to turn these rpms with a light load.

 

[Gaucho]

Re: Twin Merc 150's hi RPM & No power

Yes i can get the RPM's up to 5000-5500 and the boat does move, but at lower RPM 2000-3500 with twin engines the boat feels like it is standing still. Since am new at this am really not sure my next move to help correct this that's if it could be corrected.

 

[clanton]

Re: Twin Merc 150's hi RPM & No power

There is a bayliner owners board, if you can find it they should be some help.<br /><br />www.boc-web.org

 

[grandx]

Re: Twin Merc 150's hi RPM & No power

You must get the boat up on plane first, may require more than 3K rpm's to do so then back off some. There's no reason you cannot exceed 4000 rpm's, that's just nonsense, you need to see what your boat will do at WOT (wide open throttle) with just you in it. You should be between 5000 - 5600 rpms at WOT, if not you have the wrong props for your set up.

 

[Gaucho]

Re: Twin Merc 150's hi RPM & No power

Thanks.<br />I am able to get up to 5000-5500 which is a dangerously close to the red line. These engines are also real loud. Only once did i have the throttle all the way down and the boat was just lagging behind but i think that was because of the extra weight of water in the bilge since the pump broke. I see these other boats with twins and there moving along but i also try and keep the rpm to 4000, maybe it's just me the newbie.

 

[AndyL]

Re: Twin Merc 150's hi RPM & No power

Just a thought that if the engine set up and props are incorrect you could be getting cavitation, or one engine is robbing the others water. I assume that the engines are non-handed ie they both spin the propellers in the same direction (Normally clockwise when viewed from astern) You could try easing the power back on one when it seems to be struggling to see if it is really doing anything or just "windmilling" by the effort of the other. Then do the same with the other engine. If the rpm drops back but the boat speed stays roughly constant then it is probably the set up that is your problem. Good luck.

 

[Gaucho]

Re: Twin Merc 150's hi RPM & No power

Am going to gice it a try Friday and see what i can come up with. In the mean time is there any good books on Mercury O/B's.