alpha 1 ratio 1.84 . 260 merc 20 ft bertram

[gregdorado]

i have a 20ft bertram half cab. that i have fited whith a 260 merc gen 2 engine and transom plate. to a old type alpha 1 1.84r leg mercury specs recomend a ratio of 1.62 as the primary. 1.47 as optional. 1.81 for high alt the boat wont be used at altatude it will be used down in bass straight and tasman sea down here in oz what iwant to know is what problems or damage the 1.84ratio may cause. i have two props to try witch are a 3blade mirage 17pitch . and a 3blade aluminum 21 pitch any help is better than none

 

[Bondo]

Re: alpha 1 ratio 1.84 . 260 merc 20 ft bertram

The Standard gear ratio for a V8 engine in a Merc drive is 1.5/1.... or the 1.47, 1.48, whatever...<br />the 1.62/1 is a high alt. gear ratio for the V8s, or the Standard set for the I6s.....<br />the 1.84/1 is used for the V6s,+ the 470s.....<br />And the 1.98/1s is used for the GM, I4s...<br /><br />I'd think that with the 1.84/1 ratio, You'll need a prop in the 26+"s range.....<br />And, the lower ratio will Add to the Torque Stresses on the outdrive......<br /><br />Whatever you decide, You'll need to use the Shorter Alpha Input shaft(just over 8"s), as the Mod.1 input shaft is just over 9"s,+ can possibly cause Stress on the Engine Main Bearings(if it bottoms out in the Coupler)......

 

[rodbolt]

Re: alpha 1 ratio 1.84 . 260 merc 20 ft bertram

hjello<br /> how did you mate the genII and the alpha 1 units together? Please post me how as this may be something . like bondo said, ya may overload the gears. the alpha upper is kinda puny. change the gear oil often.<br /> good luck and keep posting.

 

[Bondo]

Re: alpha 1 ratio 1.84 . 260 merc 20 ft bertram

Good Point, rodbolt......<br /><br />He states he used the GenII Transom Plate......<br />This moves the rear motor mounts into the Alpha's 9" spacing, from the Mod.1's 15" spacing...... I Think this is where the inch of Inputshaft is lost, but I'm not Sure....<br />That brings into Question, Which Input Shaft Length to Use..????<br />I Think the 1 inch difference is in the Coupler/Transom Plate side of things, But if it's in the Gimbal Housing..????<br /><br />Now, I'm Not Sure... I've never tried to do the swap Where he is....

 

[gregdorado]

Re: alpha 1 ratio 1.84 . 260 merc 20 ft bertram

hi rodbolt i have used the gen 2 jack shaft 9.5 inches long i did try the alpha shaft it caused a few problems it only has 2 orings that are closer to the unis . the gen 2 has 3 and are slightly further along shaft towards motor. ishortened the bronze alpha lower shift shaft.abit off the top 1may be 2 mm. i then filled the sides to suit the gen2 upper shift shaft. i all so shortened the other end. but be fore that i measured the length of the tsainless shaft protruding from the lower gear housing to make sure it dosent bottom out. then i had to shorten gen2 upper shift shaft to get it as close to the housing as possible its been a lot of stuffing around but its done now

 

[rodbolt]

Re: alpha 1 ratio 1.84 . 260 merc 20 ft bertram

hello again<br /> can you post some seriel numbers? the last I looked the Gen II upper mounting was way wider than the alpha1. I am wondering if you are using various alpha1 and r/mr parts. all the alphaMR and genII shafts are now the same. the 3rd oring is for the new style couplers that have lube fittings that no one can access anyway.the only reason I ask is because if your not positive now with what you have wait 2 years when you have to order parts for it. i get some serious frankenstien stuff here and it costs the customer 75 per hour for me to research parts and what the ell did the last guy do. <br /> good luck and keep posting

 

[gregdorado]

Re: alpha 1 ratio 1.84 . 260 merc 20 ft bertram

g,day rodbolt the transom ser no is ol831264 the leg ser no od341103 it is the complete alpha leg that i have fited to the gen transom plate. the shaft is of a gen2 leg sorry but i dont have the shaft ser no handy. but i can get it in a day or if you need it gregdorado