davey buoy Posted August 22, 2012 Report Share Posted August 22, 2012 (edited) Other than the smell of rubber,which I don't have. When the coupler spins or worn,would the rpm's go off the chart. My boat is a mercruiser 86 vintage,but she can be arrogant at times. I would think just like revving in neutral if the coupler was gone. Sometimes she hits 3500 out of the hole and other times 3000rpm. At 3000 rpm's you have to work to plane it but when's she's nice, up and out in 10sec's.The difference is2 guys up front to plane and than away she goes with over 4000 rpm's . Pretty good speed for a big boat. What do you think?. Edited August 22, 2012 by davey buoy Link to comment Share on other sites More sharing options...
jedimaster Posted August 22, 2012 Report Share Posted August 22, 2012 Could be your overpitched by just a hair is it worn at all? I doubt its the splines on the coupler. Might be the prop is spun. Did you take the prop off and see what its like? Link to comment Share on other sites More sharing options...
jedimaster Posted August 22, 2012 Report Share Posted August 22, 2012 Also you may want to check with the mercruiser guys on Iboats. Some real bright mercruiser guys over there. Link to comment Share on other sites More sharing options...
davey buoy Posted August 22, 2012 Author Report Share Posted August 22, 2012 Could be your overpitched by just a hair is it worn at all? I doubt its the splines on the coupler. Might be the prop is spun. Did you take the prop off and see what its like? The prop is on a steel spline,I don't believe it has spun,if so wouldn't you get a over rev crazy!!!!!!!.Was changed from a 19 to a 17,now thinking 15 pitch would be better all around. The threeguys I had last time averaged about 160lb plus gear.Not counting me:whistling:,but I,m a constant. I also would think if the prop spun she'd rev bad also.? Link to comment Share on other sites More sharing options...
jedimaster Posted August 22, 2012 Report Share Posted August 22, 2012 Also the reason I say its not the coupler is because if its toast you are going no where and you may have some big problems. Is this an alpha or bravo? A prop hub on occasion can be sorta gone and you will sort go sometimes and not on other times. usually though it'll be a very rough ride as it will be out of balance. Easy things first. Check the prop hub and prop shaft for any damage, missing teeth etc... Link to comment Share on other sites More sharing options...
davey buoy Posted August 22, 2012 Author Report Share Posted August 22, 2012 Also the reason I say its not the coupler is because if its toast you are going no where and you may have some big problems. Is this an alpha or bravo? A prop hub on occasion can be sorta gone and you will sort go sometimes and not on other times. usually though it'll be a very rough ride as it will be out of balance. Easy things first. Check the prop hub and prop shaft for any damage, missing teeth etc... I will look at the hub,runs smooth as silk. Might be a weight load differential as I have a long front,but 200hp. With that kind of Hp,you would think the 3500 rpm would be a constant. I'll see after Saturday. Thanks for your help. Link to comment Share on other sites More sharing options...
jedimaster Posted August 22, 2012 Report Share Posted August 22, 2012 np, I know with mine(was a 130 mercruiser on a 17 footer) it was pretty sensitive. Too much booty in the back and it would be a bit slow on plane. I opted for a 14 pitch prop I could run a 17 but I had to be careful of the load alot more. I just wanted to pile in a giver without worrying about anything. With the 14 it would jump on plane with an elephant in the trunk, I was never big on top speed. Link to comment Share on other sites More sharing options...
davey buoy Posted August 22, 2012 Author Report Share Posted August 22, 2012 np, I know with mine(was a 130 mercruiser on a 17 footer) it was pretty sensitive. Too much booty in the back and it would be a bit slow on plane. I opted for a 14 pitch prop I could run a 17 but I had to be careful of the load alot more. I just wanted to pile in a giver without worrying about anything. With the 14 it would jump on plane with an elephant in the trunk, I was never big on top speed. I believe it's a alpha,prior 1990 something.V8 out drive stamped on top. The turbulence out back when getting started are second to none,quite the sight. Still will get citywide to make it a 15pitch. Still plenty of top end for me,but that's not the end all be all if you know what I mean. Still should be over 40mph,I hope, even with a elephant in the trunk. lol. Link to comment Share on other sites More sharing options...
jedimaster Posted August 22, 2012 Report Share Posted August 22, 2012 (edited) Could also be a good case for running 4 or 5 blade prop. They will help with the lower end without sacrficing as much top end as dropping down a couple inches of pitch. Edited August 22, 2012 by jedimaster Link to comment Share on other sites More sharing options...
davey buoy Posted August 22, 2012 Author Report Share Posted August 22, 2012 Could also be a good case for running 4 or 5 blade prop. They will help with the lower end without sacrficing as much top end as dropping down a couple inches of pitch. You may be on to something there!,I'll talk to him about it and see what he thinks. Thanks. Link to comment Share on other sites More sharing options...
bigbuck Posted August 22, 2012 Report Share Posted August 22, 2012 I think your hub is pooched. The rubber inside takes a beating over the years and gives out with wacky things happening. The coupler isn't the issue, if it went, you'd be dead in the water. Dropping pitch will get you out of the hole faster but where are you in the recommended rpm range?? A lower pitch prop will raise your wot rpms by 100-250. If you are looking at an overrev situation, you'll be shopping for a new engine right quick. Stay within the range. If its still slow to get on step then think about smarttabs. Link to comment Share on other sites More sharing options...
davey buoy Posted August 22, 2012 Author Report Share Posted August 22, 2012 I think your hub is pooched. The rubber inside takes a beating over the years and gives out with wacky things happening. The coupler isn't the issue, if it went, you'd be dead in the water. Dropping pitch will get you out of the hole faster but where are you in the recommended rpm range?? A lower pitch prop will raise your wot rpms by 100-250. If you are looking at an overrev situation, you'll be shopping for a new engine right quick. Stay within the range. If its still slow to get on step then think about smarttabs. Even when on plane I never go over 4000rpm. If I get 3200+rpms on take off, it gets up fairly quick.3000rpm,extra body up front to get it to plane. I believe 4500rpm on a 305ci. is ok. Link to comment Share on other sites More sharing options...
jedimaster Posted August 22, 2012 Report Share Posted August 22, 2012 (edited) Yah, make sure your rpms at wot are in the right range. If you under pitch you gotta be real careful. Also check the foam in the boat it can hold a couple hundred pounds of water if its waterlogged. Edited August 22, 2012 by jedimaster Link to comment Share on other sites More sharing options...
davey buoy Posted August 22, 2012 Author Report Share Posted August 22, 2012 Yah, make sure your rpms at wot are in the right range. If you under pitch you gotta be real careful. Also check the foam in e baot it can hold a couple hundred pounds of water if its waterlogged. I'm sure there is a bit of water logging going on. When I start trimming at wot,I can easily hit 4500rpm. Usually 3500rpm is a nice cruising speed. Link to comment Share on other sites More sharing options...
Skipper D Posted August 23, 2012 Report Share Posted August 23, 2012 (edited) I had some thing the same going on with mine second last time out , when i got looking around when i got home , i found the throttle linkage nuts at the holder had rattled off a bit and let the linkage move back and fourth , i wrenched it back to where it should be and the next time out she was back on the money , probaly this is not your problem ................. Edited August 23, 2012 by Skipper " D " Link to comment Share on other sites More sharing options...
bigbuck Posted August 23, 2012 Report Share Posted August 23, 2012 Drop down 2 inches of pitch and get a 4 blade propeller. It should get up real quick and since you aren't too worried about top speed, it's all good, you will probably increase about 100rpms at wot so at 4600, you should be fine, but with an old engine, I wouldn't run it there for any lenght of time. You should go on iboats.com forums, you can get a manual for your engine and drive for reference. Get a new style prop with the removable hub, you'll be in business for around $200 or so. Have the old prop repaired so you have a spare. Good luck! Link to comment Share on other sites More sharing options...
davey buoy Posted August 23, 2012 Author Report Share Posted August 23, 2012 Drop down 2 inches of pitch and get a 4 blade propeller. It should get up real quick and since you aren't too worried about top speed, it's all good, you will probably increase about 100rpms at wot so at 4600, you should be fine, but with an old engine, I wouldn't run it there for any lenght of time. You should go on iboats.com forums, you can get a manual for your engine and drive for reference. Get a new style prop with the removable hub, you'll be in business for around $200 or so. Have the old prop repaired so you have a spare. Good luck! The motor is solid. I believe under 200 hours on the meter. Old but mighty!!. As said earlier,I might drop one more pitch to 15,or will find out 4 blade versus 15 pitch. My 17 is hit and miss, that also I will talk to him as well. Thanks big buck. Link to comment Share on other sites More sharing options...
bigbuck Posted August 24, 2012 Report Share Posted August 24, 2012 Another thing just crossed my mind, check the gear ratio on your outdrive, it should be on a plate somewhere. 8cyls have a different ratio than a 6 or a 4. Iboats will be your friend here. Someone in the past may have pooched the drive and replaced it with the incorrect gear set. Link to comment Share on other sites More sharing options...
davey buoy Posted August 24, 2012 Author Report Share Posted August 24, 2012 (edited) Another thing just crossed my mind, check the gear ratio on your outdrive, it should be on a plate somewhere. 8cyls have a different ratio than a 6 or a 4. Iboats will be your friend here. Someone in the past may have pooched the drive and replaced it with the incorrect gear set. Lol. bigbuck,I managed to pooch two myself.I'm the guy!!!!!.When all this happened,to the book we went for specs. The drive to the best of my knowledge is oem. Tomorrow she goes out for a good run. I'll give you a up to date report than. Thanks Edited August 24, 2012 by davey buoy Link to comment Share on other sites More sharing options...
davey buoy Posted August 25, 2012 Author Report Share Posted August 25, 2012 (edited) Lol. bigbuck,I managed to pooch two myself.I'm the guy!!!!!.When all this happened,to the book we went for specs. The drive to the best of my knowledge is oem. Tomorrow she goes out for a good run. I'll give you a up to date report than. Thanks Went out for about 7 hours today. Boat ran very well. I added about 4 gallons of 94 octane to the tank prior to todays fishing trip. Would that make any difference on get up and go?. I think I will still look at options in the off season for a 15pitch or 4 blade 17 combination or whatever else is available. Out of the hole today, 20 seconds. Still a little long I would think. Any opinions more than welcome. Edited August 25, 2012 by davey buoy Link to comment Share on other sites More sharing options...
bigbuck Posted August 26, 2012 Report Share Posted August 26, 2012 Went out for about 7 hours today. Boat ran very well. I added about 4 gallons of 94 octane to the tank prior to todays fishing trip. Would that make any difference on get up and go?. I think I will still look at options in the off season for a 15pitch or 4 blade 17 combination or whatever else is available. Out of the hole today, 20 seconds. Still a little long I would think. Any opinions more than welcome. 20 seconds to get on plane is too long. It should take only a few. As for running super, you are wasting your money UNLESS your engine manual says you should. Does the engine accelerate smoothly or does it stumble or hesitate at all? When you accelerate to get on plane, is the drive all the way down as its supposed to be, how much throttle- 3/4 or more or only a little bit? Lots of questions can be asked. The drive may be OEM but is it the correct gear ratio for the engine?? You really need to confirm this. You should not need to run a 15 pitch prop on a smallish boat (less than 22 ft). That sort of wheel is what you would see on a big cruiser. If you are running the incorrect gear ratio, a prop can help but it won't solve the problem. Have you checked iboats? Link to comment Share on other sites More sharing options...
davey buoy Posted August 26, 2012 Author Report Share Posted August 26, 2012 (edited) 20 seconds to get on plane is too long. It should take only a few. As for running super, you are wasting your money UNLESS your engine manual says you should. Does the engine accelerate smoothly or does it stumble or hesitate at all? When you accelerate to get on plane, is the drive all the way down as its supposed to be, how much throttle- 3/4 or more or only a little bit? Lots of questions can be asked. The drive may be OEM but is it the correct gear ratio for the engine?? You really need to confirm this. You should not need to run a 15 pitch prop on a smallish boat (less than 22 ft). That sort of wheel is what you would see on a big cruiser. If you are running the incorrect gear ratio, a prop can help but it won't solve the problem. Have you checked iboats? Engine very smooth,drive all the way down,full throttle. Have not checked Iboats,but maybe the drive ratio is off. Will try and find the gear ratio tomorrow and let you know. Thanks again for your help. Ps. very good top end still.Just went out and could not find the ratio. Vaguely see V8 and 5.0 litre. You may be on to something.The boat once on plane ,behaves like a complete different beast. That gear ratio may have been for a lighter or smaller boat?.Defineatly no prop slippage. Edited August 26, 2012 by davey buoy Link to comment Share on other sites More sharing options...
bigbuck Posted August 27, 2012 Report Share Posted August 27, 2012 Find the serial # of the upper and lower and post them on iboats. The gurus there may be able to help you decipher them to find the ratio. Link to comment Share on other sites More sharing options...
jedimaster Posted August 27, 2012 Report Share Posted August 27, 2012 The lower unit gears in all Alphas are identical. The upper gears are interchangeable. I am not sure if you have an Alpha or a Bravo though. At this point you should really be bumping heads with guys on iboats. they will be able to sort you out. I would start with the Year make and model of your boat, also the weight and style in case people don't know that. Also be very specific. Post your outdrive serial numbers, engine size and HP rating. Also are you running a stainless or aluminum prop? Alot of people start with an aluminum 17 pitch, and it runs good, then they go to a 17 pitch stainless and they can't get out of the water. Its because the aluminum flex's and effectively lower the pitch during a blast off. Stainless won't flex much at all. I am just throwing things out there, the Iboats guys will get your out of the water in good time. Link to comment Share on other sites More sharing options...
davey buoy Posted August 27, 2012 Author Report Share Posted August 27, 2012 (edited) The lower unit gears in all Alphas are identical. The upper gears are interchangeable. I am not sure if you have an Alpha or a Bravo though. At this point you should really be bumping heads with guys on iboats. they will be able to sort you out. I would start with the Year make and model of your boat, also the weight and style in case people don't know that. Also be very specific. Post your outdrive serial numbers, engine size and HP rating. Also are you running a stainless or aluminum prop? Alot of people start with an aluminum 17 pitch, and it runs good, then they go to a 17 pitch stainless and they can't get out of the water. Its because the aluminum flex's and effectively lower the pitch during a blast off. Stainless won't flex much at all. I am just throwing things out there, the Iboats guys will get your out of the water in good time. It's a Alpha,traded in my stainless 21p for 3 repairs. The prop is aluminum. Serial #'S ,Not sure I can find them. Checked yesterday,no numbers. Love the top end that's why I'm entertaining a 4 blade/lower pitch etc. I'm pretty sure because of the top end gearing,a 15p might be the answer?. The boat is a 187 Scorpion Chris Craft/1986. Little waterlogged,maybe/maybe not. The long snout is what I think the problem is. You put 3or4 guys,coolers,big tackle boxes etc. sitting from middle to back,that,s a lot of rear drag. Will try iboats anyway. Thanks guys for your input. Edited August 27, 2012 by davey buoy Link to comment Share on other sites More sharing options...
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