Trimming

[Stumpys]

Ok, I hear alot about trimming out the motor, but I wonder if I am doing it right. <br /><br />First of all when I give it full throttle with the motor trimmed all the in, it only reaches 3800 RPM's. As I trim it out, it will go up to 4800 RPM's, and of course run faster. I trim it out until the motor start to really scream, them bring it back in. As I trim it back in while running full tilt, it will go back down to 3800 RPM's, and I will lose at least 10 MPH.<br /><br />Is this the right way? I have tried to search this subject with no success. <br /><br />Man, I know electrical better tan anything. Why can't I ever have a electrical problem? LOL

 

[LubeDude]

Re: Trimming

Ill give this a shot, but from the perspective of a Bass Boat.<br /><br />I have had three Bass boats in my lifetime, two 15', and the one I have now, an 18' With a 150 Merc on it.<br /><br />The boats Ive had, and have I have set up so that they will run the fastest with the trim at full trim when at WOT.<br /><br />If the prop starts to blow out with the trim as high as it will go, I will either lower the engine on the transom, or try a prop with more pitch or another blade. Its trial and error mostly. Depending on the boat, you can experience "Chinewalking" when trimmed out, or you may experience porposing also.<br /><br />The RPMs you are giving us tells me you are under propped to start with, I bet you have nearly 0000 hole shot with your current prop.

 

[Stumpys]

Re: Trimming

Ya, your right on the hole shot, but this is the original prop, so I figured OMC would have proped it right. Of course the prop has no markings of any kind so I do not know what I have.<br /><br />The caviation plate is level with the drain plug on the transom, so I figured it was not too low or not too high. <br /><br />Now... to plane out, I have to tuck it all the way in, and then gradually trim it out till she starts screaming. Oh by the way, I have a 1980 Bomber 16' fish and ski, about 950lbs dry weight. Not sure what the motor weighs.

 

[ivar]

Re: Trimming

What engine do you have? <br />Most 2-strokes should run at 5000-5500rpm , 4-strokes approx. 500rpm higher.<br />So it sounds to me like your prop have way too much pitch. There's also a possibility that your tach can be off or simply set wrong , giving you bad readings.

 

[Stumpys]

Re: Trimming

I have a 1978 85 HP Johnson. The guages are all new too.

 

[LubeDude]

Re: Trimming

Originally posted by Stumpys:<br /> Ya, your right on the hole shot, but this is the original prop, so I figured OMC would have proped it right.

Dont bet on it, Normally they just put a prop on it they think will be close, and expect you to exchange it if you need too, They do however owe you the right prop.

 

[Stumpys]

Re: Trimming

Thanks Lubedude...<br /><br />I just hate to spend that kind of money on trying different props, cause for one, the ole' lady will not like me spending it and she not get any money. LOL<br /><br />BTW, I agree as to the manufacturers just putting on what they think is right. I'm still not sure if I'm trimming out the motor right neither. As to them owing me the right prop, I bought this motor used, so I'm sure they will not go for that. Wish it was that simple. <br /><br />Thanks...