mercuier alpha one gen 2 .. wrong ratio !!

Riggy · May 20, 2009

I have a 1.84 ratio on my boat and should have a 1.98 ratio . needless to say it turns low rpm and is not easy getting on plane . what are some options to get rpm up and getting on plane better ! I am open to anything . maybe changing the gears to get 1.98 ratio , change prop , or trade mine for a 1.98 . Any ideas ...Thanks , James

haulnazz15 · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

It's not that big of a different in ratio, you should be able to change props to fix the problem.

fuzzybob · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

You should post more info.... what engine etc. I can tell you 1.84 is a lower ratio than 1.98 and should turn your prop at a higher RPM than the 1.98 You may have a prop issue.

Riggy · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

4cylinder 140hp .. 3 blade alluminum 14 1/4 by 19 pitch prop ... 18 foot maxum .....2200 rpm wot .. 1.98 is what is stock for my boat ....I have a 1.84 on it though ..

fuzzybob · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

You have engine problems or the prop hub is spun your tach is faulty... Your WOT rpm's should be about double what they are. The difference in gear ratio wouldn't make that much of a difference.

Riggy · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

Tach may be faulty its new . I just connected it and nothing else .

IVAZ · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

fuzzybob said:
You should post more info.... what engine etc. I can tell you 1.84 is a lower ratio than 1.98 and should turn your prop at a higher RPM than the 1.98 You may have a prop issue.

1.84 is a higher ratio than 1.98. Theoretically the RPMs should be higher as you suggest, you just have high and low mixed up.

fuzzybob · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

Ivaz, Thanks.... I'm old like dirt and somtimes my mind runs left instead right!!

IVAZ · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

bob,
I have many of those days.

Bondo · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

4cylinder 140hp .. 3 blade alluminum 14 1/4 by 19 pitch prop ... 18 foot maxum .....2200 rpm wot ..

Ayuh,.... A 15" pitch prop should bring the rpms Up,..
But,...
I'm thinking everybody is Right,+ you've got a Sick motor...

Riggy · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

The rpm of 2200 is wrong ! I took gauge off and it was set for a v8 . I just changed it for a 4cylinder so I will find my correct rpm hopefully tommorow . Thanks for all the info guys . obviosly I am new to working on boats and your help is much appreciated . Thanks , James

180shabah · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

now were getting somewhere. When you redo the WOT test, get a speed also.

MikDee · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

Riggy said:
The rpm of 2200 is wrong ! I took gauge off and it was set for a v8 . I just changed it for a 4cylinder so I will find my correct rpm hopefully tommorow . Thanks for all the info guys . obviosly I am new to working on boats and your help is much appreciated . Thanks , James

My Quote from your other thread ("Re: 1995 Maxum!! help finding correct ski prop") post #9

"Make sure your tach is set to the right number for your engine, with the settings on the back."

Riggy · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

yep , Thanks mikdee you nailed that one ! hopefully I can get it in the water and see the real rpm reading .

Riggy · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

ok I will get speed test if the gauge works " also new " ! LOL ... It hasnt worked yet , I blew the speedometer tube out tonight and replaced the o-ring around the connection at the lower unit .

scipper77 · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

Wouldn't you just double the rpm's to correct the 4 cylinder/8 cylinder setting issue? your current WOT rpm's are 4400. of course I am assuming that the tack sees one revolution based on the coil firing 8 times when in fact your 4 cylinder turns 2 revolutions for every 8 sparks.

wca_tim · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

pretty much on the last post. in addition 1.98:1 vs 1.84:1 is like a couple of inches pitch. Did the same prop turn around 4600 or so before?

Higher number, more gear reduction, higher engine rpm per prop shaft rpm. I bet a 17" prop would hit right about where you want it to...

Commissionpoint · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

wca_tim said:
Higher number, more gear reduction, higher engine rpm per prop shaft rpm. I bet a 17" prop would hit right about where you want it to...

Yeh, or the 15" wheel Bond-O suggested.

MikDee · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

He's got 1:84 gears, not stock 1:98 gears, meaning his gear ratio is presently not as low as stock, the stock ratio is almost 2x1 reduction, the present reduction ratio is almost like 1-3/4X1, meaning the prop shaft is spinning faster then normal (gears too tall), so as not to kill his engine from the load, he needs to drop down in pitch, not up,,, of course this all depends on his results

wca_tim · May 20, 2009

Re: mercuier alpha one gen 2 .. wrong ratio !!

MikDee said:
He's got 1:84 gears, not stock 1:98 gears, meaning his gear ratio is presently not as low as stock, the stock ratio is almost 2x1 reduction, the present reduction ratio is almost like 1-3/4X1, meaning the prop shaft is spinning faster then normal (gears too tall), so as not to kill his engine from the load, he needs to drop down in pitch, not up,,, of course this all depends on his results

that's why i said to go from the 19 he has to a 17....

Actually, if you do a direct conversion and assume that the new prop is as efficient as the old, an 18" with 1.84 is nearly equivelent to a 19" with 1.98...

Bondo- suggessted 15 before we learned that the tach was reading ca. 1/2....

mercuier alpha one gen 2 .. wrong ratio !!

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