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Posts: 99
| I am running a 1998 Ranger 692 which was repowered in 2007 with a 175 Pro XS (new in 07 now has 530hrs) mounted in the 3rd hole. I am carrying a 9.9 kicker motor, 4 very large batteries plus gear with two 200lb guys. The Merc has a Express 21 pitch prop which runs 50mph at 5600rpm. Up till this year I have had no issues. It seems like once this heat set in and water temps got up to 80 degrees back in early July I have been having problems. Whats happening is when I throttle down to take off the motor starts choking out. I had a dealer look at it and they say the motor runs fine in the tank and has no issues. Long story short I figured out when we come out of the hole the motor is dropping too low in the water column and covering the exhaust vent which is causing the hesitation/bog. If my partner goes up to the bow of the boat it will take off fine. I am working with Ricky out of Brainerd and he had me try out a Rev4 19p and with all 4 plugs removed the problems seems even worst. He advised me to try and raise the motor up one hole and see if that helps. I was just wondering if anyone has any insight on what is happening and if raising the motor up would help? Going up 3/4" don't seem like much? I mean when I throttle down this motor dives, seems to me it would have to go up a few inches to solve the problem. Thanks for any help, Kevin |
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Posts: 238
Location: Rhinelander | Did you by chance see the post about 690/150 merc propping? I'm sure you know the 690 and 692 in that year class are the same hull.
Lots of info about props with guys chiming in with 175 motors like yours. Rev 4 23p is what a few guys settled with.
Raising and lowering motor is something to play with and will show different results depending on load for any givven day......I have a hyd jack plate on my '97 690 with the 175 efi. |
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Posts: 42
| Sounds to me like you have a motor issue not a prop issue. You can run a motor in a tank all day long but until you take the mechanic out to the lake and hammer down on it and show him the choking or hesatation of motor then I would think he should be able to figure it out. |
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Posts: 358
| If it worked ok before but something has changed I would make a list of ALL things that you might have changed. I have a 692 with a 175 Faststrike on it and it performs well with both a 21P & 23P rev4. Tank testing cannot simulate the load your engine sees on acceleration, so it may be a trial and error till you find it. I would start by checking to make sure the fuel system is not plugged anywhere, and / or check fuel pressure.
My engine height is roughly 3 inches from bottom of the hull to the cav plate, I can measure exactly for you if you want to compare. |
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Posts: 176
Location: Tomahawk, WI | Im the person with the 98 690 with 175 Opti. I just received my 23 pitch Rev 4, i could hardly turn it, my motor wanted to quit on the hole shot, the prop i tested before i ordered must have been a 21 pitch witch worked awesome, i should of actually looked at the stampings on the one i tested before i purchased, the person who's prop i tested is going to check his stampings and get back to me this afternoon with the pitch and im betting its a 21 pitch. Sorry for any confusion. |
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Posts: 99
| Right now I am running a 19p Rev4 with all vent plugs out. Once I get on plane 1/2 tank gas me by myself I slowly bring the trim up watching my rpms and speed together on my smartcraft gauges looking for maximum speed. Max speed is 49 mph at 5600rpm. I can trim up more (over trim) and get more rpms but the speed doesn't change so that tells me with my set up (weight & distribution ect...) 5600 rpm is the most efficient running rpm with this prop.
The way Ricky explained to me on venting these props is start with all the plugs in and test run the boat. Watching the rpms closely, throttle down to WOT coming out of the hole and look for the rpm range to quickly get into the 3-4 thousand rpm band. Any more then this would be signs of prop slipage. So I took my boat out and made several runs increasing the vent hole sizing each time watching the rpms closely looking for that magical power range coming out of the hole. The best I could get mine was with all the plugs out I will get 2500-3000 rpm like right now as it gets up on plane.
My problem is...(and this is the reason I even messed with the prop to begin with)...is when my partner or my two sons get in the boat and I take off the motor bogs down and won't take off unless somebody gets up front. I know whats happening I just don't know why this is happening. You guys know that exhaust vent in the back of the motor? There like a**holes every outboard has one. When I get additional weight in the boat and go to take off the motor sinks enough where that vent goes under water to point it can't vent apparently allowing the exhaust to flow freely from the engine...so it stumbles. When the guys go up to the front deck the back of the motor comes up enough uncovering the vent and allowing the engine to breath and it takes right off like a raped ape. At least this is what appears to me to be happening. I can't seem to find a good mechanic up in these neck of the woods. Not saying anything bad about the community...let's just say they operate at thier own pace. I also believe they don't see alot of repair work cause they don't seem updated. Can anyone recommend a good mechanic with in few hours of Cass lake...I would be willing to travel. I need someone motivated and willing to put the time and effort in diagnostics, cause more than likely I do have a performance/setup problem. |
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Posts: 176
Location: Tomahawk, WI | Once bit, Thats what happened to mine last night. I have all the vents plugged solid (how it came) and about 1/4 tank of gas. The test prop i used had all the vents plugged and it was great with 2 of us sitting in the back of boat with 1/2 tank of gas (still waiting to see what pitch it is). I believe my motor is mounted on the second hole down from top, i will check for sure and get back to you on monday. Maybe the hot muggy weather last night also impacked my holeshot. |
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Posts: 99
| Pantlegger, did you try your Rev4 23p with out the vents? They pop out easy enough to do on the water. Either way once you get that pitch right you will need to dial that prop in by venting for the best holeshot. By venting the prop...it allows the motor to turn it easier initially to get you up out of the hole but yet closes once up on plane. Mine is fricken awesome out of the hole with myself only. I slam the throttle down and it literally stands up and salutes. Once I put a load in the back it dogs out. |
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Posts: 176
Location: Tomahawk, WI | Oncebit, no i havent, once i get the correct pitch i will dial it in better, There was a night and day difference between the one i tried and the one i bought, so i want to make sure it was a 21p. If it was actually a 23 pitch, than i will pop out the vents and go from there by drilling smaller and gradually drilling larger till its optimum. |
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Posts: 176
Location: Tomahawk, WI | Oncebit, i forgot to mention i also have a yamaha T8 kicker and 4 batteries for my 36v trolling motor, im about 185#s and i guess my partner was around 200#'s, his prop was awesome when we both were in the boat and the same when it was just me. |
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Posts: 5874
| PANTLEGGER - 7/27/2012 2:37 PM
Oncebit, no i havent, once i get the correct pitch i will dial it in better, There was a night and day difference between the one i tried and the one i bought, so i want to make sure it was a 21p. If it was actually a 23 pitch, than i will pop out the vents and go from there by drilling smaller and gradually drilling larger till its optimum.
Try removing just two plugs opposite each other. |
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Posts: 99
| Pantlegger, sounds like our set-up is pretty close. Yes let me know how many holes down your motor is mounted. Mine is the 3rd hole down (all the way down)...maybe that is my issue. Thanks. |
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| If you had motor since 2007 and have not had an issue up until this year why would you think it is in the prop unless you have had this problem all along and just notice it now. I have a 1998 690 vs with a 175 efi merc with a four blade custom and at 5600 rpm pulling 60 mph GPS on two units and on phone with no problems with hole shots. All vent plugs are out too. |
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| Have you added any sea foam to gas, are you running premium gas, mine runs not so good with gas with ethenol in it, have you checked your water separater? |
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Posts: 99
| Glog...I take it I must be sounding like an idiot right about now. See, when I started having this problem I brought it in to the local dealership and they had it for 10 days going thru it and they said the motor was perfectly fine...ran great in the tank and no codes were set. I asked them if they could water test it but they assured me tank testing puts more of a load on the motor than being out on the water. So the prop was the next in line, pitch down with the prop to make up for any unknown weight/balance/power differences? And heck I could try a demo prop for $25. Geez I've had all kinds of thoughts trying to figure out whats different. I thought maybe my buddy gain a little too much weight? Or the boat hull is water logged or the motor is worn out? But at this point I am pretty convinced there is something wrong with the motor regardless what the shop says. Good point on the fuel tips...I will try them out asap. Thanks. By the way...what did it take to get your custom prop? |
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| My dad has been a mechanic for over 50 years and I have learned allot from him, gas has been a number one issue in the last five years. Tank testing does not give proper diagnostics when motor is under load. dah props in Wisconsin , others on this site have used them and also have been very pleased. If things have been working great for five years just dont understand why it would be a prop issue. |
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Posts: 42
| Its not hard to get confused especially when you have had someone look at it and say its not the motor.hell I have a 2009 gmc with 24,000 and in hot weather sometimes it doesnt want to start had it in four times under warranty and they cant figure it out!!! Did you buy the motor from the guy who is working on it?
Edited by glog 7/29/2012 2:00 AM
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
Couple of thoughts here that might be part of the issue.
First, when air and water temps go up, your boat will actually sit lower in the water by a touch, and the motor has to work harder to push the boat out and up. The second thing that happens is with hot humid temps is your motor will not make as much HP as if it were low humidity and 70 degrees out.
Neither of these should cause that much issue with your boat, so I am wondering about the positions of things within the boat. I noticed you mentioned 4 big batteries, a kicker, etc. Are the batteries in the back? Is your fuel tank full as well?
In considering the prop, that rev4 has been a good combination due to the boat design, but vent holes can be a really tricky thing. If all 4 vent holes are wide open, those are pretty large holes and a bunch of exhaust is going to escape from them, even at that 3000 rpm range. THAT is right around the range you want your motor at to be popping out of the hole when you punch it.
I think Shep hit it right.... plug two holes fully, then work your way to larger holes on the other two. Your boat may need more forward thrust happening before hitting it.
Oh...one other thing to at least take a look at...on the motor mounting itself, where is the stop-bar when the motor is trimmed down all the way. Is it in the lowest possible position or one up? If it is any further up (or out) that will cause the bow to rise more and the stern to dig more, which could also be part of the issue. If that bar is not down all the way, I'd see about moving it to the lowest possible position which will allow the motor to tuck under more, giving you more stern lift on hole shot.
Raising the motor will get the boat higher in the water overall on plane, and it might help with the exhaust issue, but I don't think that is where the issue is...I think it is in the prop itself.
Steve
Edited by VMS 7/29/2012 8:17 AM
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Posts: 13688
Location: minocqua, wi. | hey guys ... i think pantlegger's prop concern has been solved. the prop he ran with success was confirmed yesterday to be a 21P Rev4. the confusion solves that piece. |
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Posts: 183
| I left this on another post Take a moment and check out this website http://www.mercuryracing.com/blog/walleye-prop/ Scott will answer any questions you have. I went with this prop on my 1890 Tuffy with excellent results |
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Posts: 3508
Location: Elk River, Minnesota | and Kirt,
how much $$ did you drop on that prop?
Steve |
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Posts: 183
| Oh boy, I have to dig out the invoice to give you real number. I will get back to you. They have to versions the lab finish is quite a bit more than the pro finish, i got the pro finish.
I was running a 21 Tempest and a 21 Rev 4, the Bravo you have to step up to a 22p, Scott can answer questions on your boat
Edited by kirth 7/30/2012 6:04 AM
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Posts: 176
Location: Tomahawk, WI | OnceBit, My motor is mounted in the 4th hole from the top out of 5 possible holes. |
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