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Kylersk

Tested out my new Opti and have a few questions..

18 posts in this topic

I have a new merc 115 optimax with a 19 pitch, 13" aluminum merc prop. This is pushing a 2000 Crestliner sport fish. Since today was the start of the break in, I did a couple laps around waconia changing the throttle the whole time. I think I was out there for about an hour or so?

Anyways, On to my questions...

1.) The motor sounded nice when trimmed all the way down. When I trimmed it up a little, it sounded louder and the RPM's may have been up? It almost sounded like the prop was not completely under water? Like I said, I didnt trim it up alot. On my trim gauge if I brought it near middle trim, that's when it sounded odd?

2.) I ran the motor most of the time between 2000-3600 rpms. Near the end of the time, I pushed it to full throttle, but only for a very brief moment. At full throttle I only got about 4500 rpms and a top speed of 33mph. Since it was such a brief moment at WOT, I didnt get the speed. But when I got home, I checked my GPS and it stated the top speed reached was 33mph.

Thoughts?

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If by 2000 crestliner you mean like 20 feet, then 19 is a pretty high pitch. An initial guess might be that it is too high.

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sorry, it's a year 2000 1750 sport fish.

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Quote:

sounded louder and the RPM's may have been up


When this happens again, watch your rpm gauge. Trimming a motor out will lift the boat, make it run faster and more efficient, will get the motor's exhaust closer to the surface (louder), and will increase your rpms. They should increase steadily, as much as 400-600 rpm gain from trimming out your motor. I run my boat with the motor down for holeshot, then trim it out as far as I can when running.

If your rpms shoot up instantly, like 1,000 or more, instead of steadily climbing about 500 rpms, then your motor is cavitating - there's air by the prop and it's not biting in the water. The quick remedy is to trim the motor in more.

For now I would rely on your tach, not your trim gauge.

If the motor is cavitating, then you need to work with your dealer for things like changing props or changing the mounting height of your motor.

Quote:

pushed it to full throttle, but only for a very brief moment. At full throttle I only got about 4500 rpms and a top speed of 33mph.


Those rpms and top speed are too low. For starters, did you have the motor trimmed out as far as possible - that's where your rpms will go up and your speed should really go up, unless you have a cavitation problem. If you are trimmed out all the way and not cavitating, you need a different prop and/or to have the motor raised to get your motor operating in its peak range. With a 115 you could get some benefits by going to a stainless prop, but you need to do some more testing / running before you start trying different props. Get the motor broke in, then run WOT for long enough to play around with trim and max out the rpms and speed. And try it with a light load in the boat and a heavy load in the boat, to see what it does under those circumstances.

It's all part of getting a new boat set-up, I'm sure your dealer will help where needed. Good luck.

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PerchJerker had great advice, wait for a while until motor is broken in and you can actually test it WOT.

I am sure you are still running with it trimmed in too much.

It takes a little practice with trim to find the "spots" you want. You'll be able to get a position where max speed is achieved and still have good control of boat, then in the turns you might get a little cavitation and you'll have to trim down. Also when you trip up the bow of your boat will raise out of water, with motor down it will plow, the fastest is when boat is out of water but not too much to be uncontrollable.

It takes a little practice but you'll get it mastered quickly.

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Perch and Valv are right on. Before I would worry a lot about the prop I'd wait until you can run it at WOT with the motor trimmed out to the right spot, then start dialing in on a prop. It does sound to me like the dealer should have installed a lower pitch prop, but wait until you can get a good run on it at WOT before making that call.

marine_man

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I didn't catch the 19" pitch, sorry. I agree with others again, it might be too high pitched for a 1750 and a 115hp, you might have to get down to 17". Just go one step at the time, finish break in them get on the details.

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I have a Trophy Plus 17P 4-blade on my 90 Yamaha and it trolls a bit faster than I'd like. I think I'm going to a 3-blade 16P. I wonder what the diameter of your prop is and maybe you could try my 4-blade with the 17P to see if it helps?

Like they said above though, probably get some more seat time in that thing and see how it works for a while. Play with the trim until either it starts to blow-out or porpoises. That will be as far and as fast as the boat will go at those RPMs of whatever you find at that speed. Is the motor mounted too high and it's already cavitating at less trim angle?

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The prop swap would be great, I believe Yamaha and Mercury have same propshaft style

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Thanks for all the replies! That's what I love about this site.. A total newbie can get tons of help.

Anyways, day 2 went far better. I played with the trim, at home in my driveway to see what the gauge said and where the motor was. Looking at it, it looks like half trim, on the gauge, is actually on the outer edge of the trim range. On my old motor, half trim was half trim.

I toyed around for about 2 hours today, varing the rpms the whole time and 'learning' how the trim affected the boat. After I got comfortable, I did a few short runs at WOT. My max speed was 42mph (gps) with my rpms hitting about 5200.

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Those numbers sound much better.

You are probably at the lower limit of rpms for your boat (I don't know for sure), but the 19 pitch prop is probably going to be the fastest for you. If you run with a heavy load in the boat, your rpms may be under the lower limit.

I'd say use your boat some more, and try it with a couple good sized guys in there, and see what it does. You may have to raise your motor to raise rpms, or drop down in pitch which will give you more holeshot, more accelertion, more rpms, and better handling with a load --- but may cost you 1-2 mph on the top end.

Good luck.

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I have this exact motor on a similarly sized boat. My hole shot was not good with a heavy load, so I switched from the 19P to the 17P. Big improvement. Also, my trolling speeds slowed down almost 1/2 MPH, which I think is great. I did lose 2 or 3 MPH on the top end though. I can still get over 40 MPH though. You really should follow your break in schedule. If you have any issues, the repair shop can tell exactly how you have been running your motor (or so I am told).

My motor is also a little louder with the 17P. I don't know why though. Overall, I have been pretty happy with my motor.

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Sounds like Run 2 was much better...

Like Perchjerker said, get a couple of guys in the boat (or, from another perspective the load you typically run while fishing) and see how your holeshot is. If it takes a long time to get on plane I'd seriously consider a 17 pitch prop.

Actually, if it were me, I'd finish your break in, but seriously consider a 17 pitch prop. I'd get you back up closer to the high end of the recomended RPM range of 5000 - 5750. You're holeshot would be great, and yes, you'll loose a couple of mph, but I'd rather have the holeshot in this size of boat. It's not like you're after 50 mph.

LMITOUT's proposition sounds pretty good too... a 4 blade would probably be pretty good on that rig...

marine_man

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Quote:

You really should follow your break in schedule. If you have any issues, the repair shop can tell exactly how you have been running your motor (or so I am told).


Maybe I'm reading too far into that statement, but I believe I'm following the break-in schedule.

According the the schedule it says to run the first hour at varied RPMS (mostly in the 3000-4500 RPM range) with occasional 10 second bursts at WOT. For the next 3-4 hours, you can run it in any RPM range, but for no more than 10 minutes at a time.

First day I had probably 45 minutes on the motor. Tonight I added another hour and half or so.

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Break-in is the most painful part of a new boat. I'm in the process of that myself and my schedule calls for an hour at no more than 2000 RPM. That's not even on plane so it's just plowing water around the lake. Pretty boring. I've got past that already and started to get on plane more and easing up to WOT at short bursts.

My dealer recommended to keep the motor tucked in to put a lot of load on the engine to help break in. I believe the engine manual said the same thing as well. Put some temperature into the engine and get everything seated well. Some say if you don't "get on it" a little the rings will never seat and you'll have an oil burner. Everyone has their own opinion on break-in but I'm doing a little of both. Get some heat into the engine and then let it cool down for a while then repeat but never keeping the RPMs steady for very long. I think that the first hour or so is probably the most important to let everything mesh for a while without a lot of stress.

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What I dont understand is.. Why have the consumer do the break in? If the break in is "important to ensure proper performance and maximum life from the engine", why not have it done BEFORE the consumer recieves the engine? Doesnt Evinrude have a "no break-in" policy? Then again, I did blow a 2000 evinrude.. So who knows. confused.gif

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You didn't blow the Evinrude, it had problems on its own, probably hidden from previous owner.

I was at a delaer few years ago buying some overstock boats, they had a 1 year old Maxum 21ft boat with the bottom COMPLETELY ripped off. Previous owner damaged it on a reef, had it patched up and painted, then traded it for a new boat. Dealer didn't find out until next water try after pulling boat on trailer, and saw 75% of bottom was coming off, and when I say the bottom coming off I mean the whole fiberglass bottom was open !!!! shocked.gif

Beautiful, boat on top, but could not float very much.

Many mfg of motors let end user finish the break in, if you buy a weed trimmer you have to take it easy on it for few times. Just sit back and enjoy a great motor, I love Optimax es (is it a plural ???) I think they are what's left of the true outboard from the past minus fuel consumption.

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Quote:

Break-in is the most painful part of a new boat.


Get a boat with a kicker motor, then you'll have twice as much break-in to do shocked.gif

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