Re: 90hp Mariner Gear Ratio?????
THANKS GUYS!!!!, i really appreciate the info. To the last poster what type of boat are you running this engine on and what speeds are you getting with your prop combination? I just purchased this boat at the end of last season and it is a 17' spectrum deep v boat propped with an alum 21P 3 blade. MY top speeds were 34 MAX.... However the rectifier was shot so i was not getting a signal to my tach, i replaced this over the winter to give me a clue of RPMS im running. Id like to re prop to get soem better performance. But dont have all the info i need yet to start looking. Just tryign to get some comparibles, as i have no idea if 34mph is slwo for this HP motor. thanks
As I said, I essentially have that engine on a 17' alum BB that weighs 700# dry, but with me and batteries/fuel and other gear, it probably is up in the 1400# range. It does have a 3 tier stepped hull which reduces hull contact with the water at higher speeds and I have hit 50 exactly GPS on a cold day in calm water (regularly can run 48) with just myself aboard. Picture in my Avatar is the wake at the time.
I'm running a Ballistic XP 24P SS which I bought from this site for not much over $200 several years ago...obviously it was on sale. I turn a solid 5600 rpm at WOT. Like all the prop experts tell you, until you mount a prop and run it, you just don't know....it's just speculation, but some of them can speculate very close to actuals.
I have 4 props for this boat (17SS, 21SS, 23 alum, and this one). Obviously I walked my way up. I bought the rig with the 17 with the boat 2 years old; can't imagine the orig. owner ran this boat for 2 years like it was. The boat was so under propped that you got whiplash on hole shot and you don't want to know the numbers on the tach at WOT. Matter of fact, on my first time out, I hit WOT once and never again with that prop. Took her home and bought the 21.
In my opinion the dealer (I have his name and he is a big dealer in the Dallas area) who sold the orig. owner the boat didn't pay attention to the fact that the gearbox is 2.3, not 2.0 and the 17 was not near enough pitch. On a 2.0 (like the 100+ Mercs of the year) it would have been just about right but, thinking about it, with the added hp, it wouldn't have been right for them either.
A given pitch SS will outperform the same pitch alum hands down and with the different blade shapes (bow lift, stern lift, hole shot, high trim setting grip, and all the other variables) you just can't compare them. Right off the bat, with the same pitched SS of probably any brand/model, you would probably pick up a couple mph with an increase in rpm's also.
Get in the prop section and ask the question.
Mark
