Prop selection 1989 Mariner 90

I just got a 16.5' glastron Sierra bow rider with a 1989 mariner 90 hp two stroke serial 0a741178. The prop on it now is completely thrashed and the boat has no bite in the water at all. I'm wondering what size and pitch of prop is best? Can't see any numbers on the old prop anywhere. I will do some wakeboarding but I also want a decent top speed.

Thanks!

Re: Prop selection 1989 Mariner 90

Picture of the boat hull primarily including what it looks like at the transom. Altitude where you run if over 1000'. What kind of passenger load do you NORMALLY carry? Do you use water toys or ski; you said that you do some wake boarding meaning you don't have the toy connected to the boat, but you have the boat in an attitude to produce the worst possible wake.....worst stress on the engine other than the hole shot which happens in a few seconds? I have that engine in a later year model and can get you pretty close.

Mark

Re: Prop selection 1989 Mariner 90

Check for numbers near the base of the blades or under the prop nut.

Re: Prop selection 1989 Mariner 90

I don't run much above sea level, definitely under 1000ft, mostly around 150m above. I usually have three passengers and my dog, say 600-700 lbs. I'll take a pic of the hull tonight. It's a 1989 Glastron Sierra 170. I will likely be wake boarding fairly often, but also want a decent top end for cruising and getting to a good spot.

Thanks for the help!

Re: Prop selection 1989 Mariner 90

I have a spare prop(bent) that came with the boat, it's 12.75x21p. I've never tried that prop and I can't tell the numbers on the installed prop, although it cavitates so bad it wouldn't give me an idea of how the pitch feels anyways. I've never run a good prop so I really don't have any base point to work off. Max rpm should be in the 5500 range.

Re: Prop selection 1989 Mariner 90

Boardwild33 said:

I don't run much above sea level, definitely under 1000ft, mostly around 150m above. I usually have three passengers and my dog, say 600-700 lbs. I'll take a pic of the hull tonight. It's a 1989 Glastron Sierra 170. I will likely be wake boarding fairly often, but also want a decent top end for cruising and getting to a good spot.

Thanks for the help!

Click to expand...

With the A-Z shopping list you have, you can't have it all with one prop.

Mark

Re: Prop selection 1989 Mariner 90

I realize a prop will always be a trade off, I just don't want to get too high of a pitch that I can't get up on plane while towing a wake board. I know I won't have the best of both.

Re: Prop selection 1989 Mariner 90

Not familiar with a wake board. Do you tow them like water skis and drive slow to make a big wake and the rider guides the board over and across the wakes like a big fat water ski? To me that is a big load with the board and pushing all the boat that's down in the water to make the big wake. You want a pretty shallow pitched prop. To get propped properly for that you will way overrev when running light so you will have to cut the throttle back to stay around the upper limit of rpms that your engine's rating.

21p for that engine and that estimated load is way too much. I am currently running a 21 ss on my 17' alum boat with 2 folks which I can also run a 24 on. It's light and fast and I don't linger making a big wake nor towing anything. The 24 is the right prop for rpms, the 21 runs 1000 over max when I check it so as I told you, I throttle back to hold the 5500 or so limit. I run the 21 when my girlfriend is aboard as she likes the noise and fast response.

Sooooo I don't even know where to start guessing. Best thing would be to find a dealer or prop shop that would let you borrow and test a prop before you bought it. Even if you paid $100 over what you may pay for one on here you could very well get the right prop to do the job for you.

Or, you could buy alum props for around $100 each and just swap till you get it. They sell them on here. Besides you would have spare props for whatever occasion. 3 of those would be cheaper than what ss props go for so you aren't all that bad off.

17p would be as good a starting point as any. On the 2.33 gearbox your (and my) engine have, a 17 will give you a lot of thrust and not load the engine. I have one that came with my little boat and it will snap your neck on hole shot......on my little, light boat.

Looking at the top of the page at props and clicking on that looking at Merc and pitch of 17P you get a long list of available props. The first listed is a Solas Amita P/N 1411-133-17 for $101. Apparently it has the rubber hub so no separate hub is listed. Besides you get free shipping! Can't beat a deal like that.

So, since you asked for help, help yourself. Get this prop and try it. See how it performs with your water toys and all and then get the WOT rpms. If you can go over 5500 go head and punch it up and get the number. Then come back on here with your results.

For what's it's worth I have pegged my tach hard on my current engine and the tach pegs at 7000. I was fooling around with it one day working on a problem and it took off on it's own. Besides I currently run 5700 on my 24p and my 21 will firewall at 6500.....but I cut it back to 5500-6000.

Waiting for your results.

Mark

Re: Prop selection 1989 Mariner 90

Yea you got it, same as slalom(in terms of pull needed to get out of water), but we run slower to give the bigger weight, pros will also load the crap out of the boat (including filling water ballast) to get a bigger wake.

I stopped into my local marine supply store and after talking with a tech I decided to go for the 13x19p to try out this weekend($100 even and in stock). This weekend will mostly be cruising but ill keep you posted on the rpms and the holeshot feel.

Thanks for all the help mark, I appreciate it!

Re: Prop selection 1989 Mariner 90

Have fun and keep us posted. Remember, don't hit anything what that prop, sand bars included....TLC and it's still his, otherwise, it's yours.

Mark

Re: Prop selection 1989 Mariner 90

Water test last night worked great! Awesome holeshot getting up on plane in about 4-5 seconds. Wot was spot on 5500 and hit 40mph! I haven't tried to actually wakeboard but I don't think it will be an issue, seems like a decent all around prop size for me.

Re: Prop selection 1989 Mariner 90

Boardwild33 said:

Water test last night worked great! Awesome holeshot getting up on plane in about 4-5 seconds. Wot was spot on 5500 and hit 40mph! I haven't tried to actually wakeboard but I don't think it will be an issue, seems like a decent all around prop size for me.

Click to expand...

Man I really don't want to rain on your parade, but towing toys takes a lot of whoopie and the numbers you posted without toys are perfect. With toys I'd guess dropping down to a 17 in the same mfgr./style prop would do it for you. You will just have to watch the rpms when you are running light. You can run back up to your 40 with less pitch.....at least I can do a similar thing with my engine but people "roll they eyes at you" when you go over the recommended WOT rating......but it's your toy just like mine is my toy and I run it where I want. Course 2" pitch unloaded is like 300 to 400 rpm so you are still under 6000 and I have my last 2 Mercs including the current one that 6k didn't bother me at all and the engines just loved it. Seems the less load on them the better they ran and dropping to a 17 will lighten the load when not playing with toys. People blabber about your torque curve, but the torque curve on my Mercs must be flat to infinity because they just keep shoveling the fuel to the ponies and the ponies keep humpin it.

HTH,
Mark