Mister G Posted May 21, 2015 Report Share Posted May 21, 2015 It has power trim, maybe I was to much over trimmed, and they are installed in the second or third hole This statement doesn't sit well with me. If you have power trim/tilt your motor should be set on the last (lowest) trim hole so you have full trim capabilities. Do this before spending a lot of money on a new prop. Link to comment Share on other sites More sharing options...
shimano19 Posted May 22, 2015 Author Report Share Posted May 22, 2015 I would still like to know what prop the OP has on his boat currently. Diameter and pitch. Not sure the diameter but the pitch is 13. MisterG I got my boat second hand, the motor was mounted by the marina on the 3rd hold from the top. i can tilt the motor up and down by a button, when I start I trim all the way down, and the prop faces down slightly rather than horizontal Link to comment Share on other sites More sharing options...
BillM Posted May 22, 2015 Report Share Posted May 22, 2015 It should be stamped right on the prop 13-XX Link to comment Share on other sites More sharing options...
shimano19 Posted May 22, 2015 Author Report Share Posted May 22, 2015 F10.38x13p Link to comment Share on other sites More sharing options...
Sinker Posted May 22, 2015 Report Share Posted May 22, 2015 Whats the height of the cavitation plate in relation to the bottom of the hull? S. Link to comment Share on other sites More sharing options...
DRIFTER_016 Posted May 22, 2015 Report Share Posted May 22, 2015 (edited) Not sure the diameter but the pitch is 13. MisterG I got my boat second hand, the motor was mounted by the marina on the 3rd hold from the top. i can tilt the motor up and down by a button, when I start I trim all the way down, and the prop faces down slightly rather than horizontal According to the prop chart I posted that prop should work properly. Can you post a pic with the motor down looking @ the back of the boat? It's possible the motor is not mounted high enough and causing too much drag. With the motor straight up and down the cavitation plate should be about 1" below the bottom of the boat. Take the pic from a low angle (cavitation plate height) so we can get a good look. Edited May 22, 2015 by DRIFTER_016 Link to comment Share on other sites More sharing options...
Stef Posted May 22, 2015 Report Share Posted May 22, 2015 Yeah... motor mount to position the cavitation plate not being correct sure fits the symptoms being described to a tee. Prop pitch changes are a fine tune item about 200-300 RPM per inch of pitch change so not likely. Also, I had one coil pack go out so it was running on 3 cylinders on mine, same symptoms but running a bit rough which the OP might not detect as he has not had any experience with the motor running properly yet. It will start and run on three cylinders with no problems... Link to comment Share on other sites More sharing options...
DRIFTER_016 Posted May 22, 2015 Report Share Posted May 22, 2015 Yeah... motor mount to position the cavitation plate not being correct sure fits the symptoms being described to a tee. Prop pitch changes are a fine tune item about 200-300 RPM per inch of pitch change so not likely. Also, I had one coil pack go out so it was running on 3 cylinders on mine, same symptoms but running a bit rough which the OP might not detect as he has not had any experience with the motor running properly yet. It will start and run on three cylinders with no problems... The coil pack thing could be another thing. Had it happen with my new 115 when I installed it. Motor ran great, started great, was smooth but wouldn't top out where I thought it should. The problem was the on plug coil pack on the bottom cylinder was not properly plugged in so it wasn't firing. I pulled the plugs one at a time to check how they looked. Top three looked normal grey/tan but the bottom was like clean and had never been fired. Made sure I pushed the connectors until a heard and felt a positive snap and the issue was resolved. Link to comment Share on other sites More sharing options...
NANUK Posted May 22, 2015 Report Share Posted May 22, 2015 Are you sure 13 is the pitch ? Sounds like diameter to me Link to comment Share on other sites More sharing options...
DRIFTER_016 Posted May 22, 2015 Report Share Posted May 22, 2015 Yes it's the pitch. Diameter is first on the prop sizing. Also pitch is sized in whole inches not fractional. Link to comment Share on other sites More sharing options...
shimano19 Posted May 22, 2015 Author Report Share Posted May 22, 2015 (edited) I'll check the plate and make sure the coils are plugged in correctly once I get home. Thanks Edited May 22, 2015 by past.the.cast.mike Link to comment Share on other sites More sharing options...
scugpg Posted May 22, 2015 Report Share Posted May 22, 2015 If it's mounted on the 3rd from top holes I'd be surprised if the cav plate isn't close to the bottom of hull except if it's an x-longshaft motor. Link to comment Share on other sites More sharing options...
DRIFTER_016 Posted May 22, 2015 Report Share Posted May 22, 2015 I'll check the plate and make sure the coils are plugged in correctly once I get home. Thanks Do yourself a favour if the coils are plugged in properly check the plugs to make sure they have all been firing. Could have a dead plug if it is not the coil connection. I bought brand new plugs for my old engine once and had a dud. Link to comment Share on other sites More sharing options...
Big Cliff Posted May 22, 2015 Report Share Posted May 22, 2015 (edited) Have the same engine on a Princecraft 164. Top speed about 32 mph, I never push mine past about 5000 rpm but it will go a little higher. On plane in under 30 seconds with one or two people in the boat, a bit longer with 4 people depending on where they are sitting. Excellent engine, quiet and fuel efficient. Bought mine new and baby it a bit but love it to pieces. Edited May 22, 2015 by Big Cliff Link to comment Share on other sites More sharing options...
DRIFTER_016 Posted May 22, 2015 Report Share Posted May 22, 2015 DANG!!! 60 seconds to get on plane? I thought my boat was slow. With the old 90 two stroke it took me about 2-2 1/2 boat lengths to get on step. With my new 115 four stroke and spitfire prop I get on step in a boat length!!!! Link to comment Share on other sites More sharing options...
Big Cliff Posted May 22, 2015 Report Share Posted May 22, 2015 Sorry, re thought that, not 60 seconds, more like 30 or less. Link to comment Share on other sites More sharing options...
shimano19 Posted May 24, 2015 Author Report Share Posted May 24, 2015 With new 11 pitch prop I hit 31mph at 6100rpm but I don't like pushing it past 5800rpm so I keep it there and get about 28mph with 3 people. Still lower than other people are getting. Merc says this motor performs best at 5500-6000rpm Link to comment Share on other sites More sharing options...
scugpg Posted May 24, 2015 Report Share Posted May 24, 2015 Good to hear you got the rpms up but yes they're a little high. Any chance you could try a 12p? Might strike the right balance for your setup. Link to comment Share on other sites More sharing options...
shimano19 Posted May 24, 2015 Author Report Share Posted May 24, 2015 I'm thinking about doing that, I wonder if I'll get the same speeds with the 12. With the 11 if I adjust the tilt to sit level I can have it at WOT and just below 6000rpm. As I raise the tilt I will gain more rpm so I'd have to let off the throttle Link to comment Share on other sites More sharing options...
scugpg Posted May 24, 2015 Report Share Posted May 24, 2015 Might even be slightly faster with a 12. Link to comment Share on other sites More sharing options...
shimano19 Posted May 24, 2015 Author Report Share Posted May 24, 2015 Why do you say that spooled? Link to comment Share on other sites More sharing options...
Sinker Posted May 24, 2015 Report Share Posted May 24, 2015 It will drop rpms, and increase speed. Prop pitch is basically inches of boat travel per turn of prop. 12 pitch, 12" per turn......something like that anyways. You were over propped with the original, now slightly under propped. 12P should be the sweet spot. S. Link to comment Share on other sites More sharing options...
scugpg Posted May 24, 2015 Report Share Posted May 24, 2015 (edited) Higher pitch generally results in faster speed but lower rpms. So if your maxed out at 6100 with the 11p but can still be in the optimal 5500 to 6000 with the 12p, you could get a bit higher top end. That was my experience when I was experimenting with a 13p and 12p prop a year or two ago. Handy link about pitch and rpm http://boatpropellers.iboats.com/propeller-tutorials/rpm/ Edited May 24, 2015 by Spooled Link to comment Share on other sites More sharing options...
cowanjo Posted May 24, 2015 Report Share Posted May 24, 2015 Mike just got the boat back yes 3 blde 12P - I actually have the 11 as well Link to comment Share on other sites More sharing options...
DRIFTER_016 Posted May 25, 2015 Report Share Posted May 25, 2015 Now if you switch out that 11" 3 blade prop for an 11" 4 blade spitfire prop you will drop just below 6000 RPM @ WOT stay bout the same or a wee bit on the top end plus it will get on plane sooner and corner like it's on rails!!!! Link to comment Share on other sites More sharing options...
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