Brent B Posted May 16, 2016 Report Share Posted May 16, 2016 Hello everyone, I have a 95 Redfisher 18 with a Yamaha 115 2 stroke V4 pro. When i'm running full throttle and trimmed out i'm only getting about 36 MPH and my RPMs are at 4800 WOT. This is loaded how I would normally fish. 2-3 people some gear. 2 batteries in the front hatch. trolling motor up front. I have a Manual jack plate and its set perfect for how I have it loaded. My cavitation plate is right at the top of the water. Prop is not cavitating. It has a good hole shot. Everything else is factory. Not really sure if i'm just expecting too much or I have a problem. I would suspect a better prop might help but if I lower the pitch to gain WOT RPMs my top speed will suffer right? I don't have the exact prop dimensions but I will try and get them. Just doesn't add up. Maybe a engine concern? I notice that if i'm running and I give it full throttle the last little bit of throttle has no change on RPMs or speed. Its just dead space. At 4000 RPMs i'm running a solid 30 MPH. Any thoughts? Link to comment Share on other sites More sharing options...
Lap it Up Posted May 17, 2016 Report Share Posted May 17, 2016 Need more info. What prop are you running? Pitch? Diameter? How much setback? Engine height? How much trim angle? Tabs or no tabs? A lot of things come into play when trying to increase mile an hour. You should think about moving trolling batteries to console. It balances the boat much better. I run 3 group 24's in my console. You say you have a Manual jack plate and it's set perfectly. Manual jackplates can be used on these boats but they are not ideal. Personally I would remove it and mount to transom or find a 6" hydraulic. Link to comment Share on other sites More sharing options...
trf97 Posted May 17, 2016 Report Share Posted May 17, 2016 It really sounds like your WOT is low for that motor. Your WOT should be very close to the max when under load. I think it should be closer to 5500 for that motor but someone else should chime in and give you that number for certain. Link to comment Share on other sites More sharing options...
Lap it Up Posted May 17, 2016 Report Share Posted May 17, 2016 5,500 rpm for the 115 and 6,000 for the 130. Link to comment Share on other sites More sharing options...
Brent B Posted May 17, 2016 Author Report Share Posted May 17, 2016 I know the manual Jack plate is not ideal but the boat seams to run about the same if not a little better with it on. I have the run the boat both ways. With it and with out it. I have a 5.5 inch set back and the motor is raised about 1.5-2" above where it would normally sit on the transom if it was bolt as low as the engine could go. When I'm running at 30mph with the boat loaded how I would normally run it the cavitation plate is right at the top of the water. There is no water rushing over the top of it. When I say I'm trimmed out I mean I have the bow slightly out of the water but not so high as to make the boat porpoise. I'm running a stiletto 13 diameter 19 pitch prop stainless. No trim tabs deployed. Since I moved the batteries from the counsel to the anchor locker in front of the fuel tank I noticed the boat runs better for me. Again I ran it both ways and it never made a big difference in performance. Link to comment Share on other sites More sharing options...
mulligan Posted May 17, 2016 Report Share Posted May 17, 2016 Something does not seem right. I had a 97 Bayfisher with a 115,which is heavier and slower. One of the props I had was a 19 Stiletto. While not the best prop I ran it got better numbers than what you are seeing. Off the top of my head it ran mid-40s on a good day @ 53-5400. I do remember it being one of the faster props I ran. Link to comment Share on other sites More sharing options...
Brent B Posted May 17, 2016 Author Report Share Posted May 17, 2016 Just talked to Ken at prop gods and recommended a power tech 3 blade 13.5 diameter 15-16 pitch prop. Say I will get my rpms and pick up some speed. Any thoughts? Link to comment Share on other sites More sharing options...
mulligan Posted May 17, 2016 Report Share Posted May 17, 2016 It depends on the prop. There is a lot more to props than dia, pitch, and number of blades. Some are going to be easier to spin than others. Since he recommended running a PowerTech a call over to Marcus might be a wise idea. Just taking a stab in the dark here but if the prop is PTR a 15-16 might work out but if it was the SCD,which a lot of lappys like, it might not be enough. Good news is from what I have heard PropGods has a good exchange program. Link to comment Share on other sites More sharing options...
Brent B Posted May 17, 2016 Author Report Share Posted May 17, 2016 Yeah I hear what your saying about different props run different even though they are the same pitch and diameter. Yes prop gods and power tech both have good exchange programs. Who is Marcus? He works at power tech? Also I mainly want to know and make sure that what I have is a prop issue and not a power issue. My engine runs flawless and I don't think there is a problem but I just wanna make sure that I'm not knocking off 3-4 pitch sizes to get my engine where it needs to be if it's an engine concern. Seems like there is a lot of lappys running 17 pitch 4 blades. it sounds like I need a new prop but I will do a little more research and gather some more info and insight and see what happens. Any body in south Florida got a comparable prop to what I'm looking they can let me try? Link to comment Share on other sites More sharing options...
mulligan Posted May 17, 2016 Report Share Posted May 17, 2016 Yes, Marcus is PowerTech and a wealth of knowledge. FWIW I ran everything from a 16-20 pitch but mostly in the 17-19 range. This is without a jp and batteries in the console. The boat was not too picky about props but liked some more than other depending on how you wanted the boat to run. Link to comment Share on other sites More sharing options...
lurem Posted May 18, 2016 Report Share Posted May 18, 2016 Brent B, Lap it up and Mulligan have had similar boats and are a wealth of knowledge on props. I would look in your area for some props in the size you are looking for and borrow before you purchase if possible. Propgods is great too. That boat should be a low to mid 40 mph boat when its on the top of its game. Don't give up you have a great boat! Link to comment Share on other sites More sharing options...
Brent B Posted May 18, 2016 Author Report Share Posted May 18, 2016 Ok so i have talked to Ken at Prop Gods and Marcus at power tech and both agree i have the wrong prop. Marcus did mention that my top speed is to low for that prop though which makes him think that maybe either my boat is heavy for some reason or my engine is not putting out its full potential. SOOOOO has anyone had any power lose issues with these older 2 stroke engines they would like to share. At WOT trimmed out i can only hit about 4700 RPMS and 36-37 mph. Is there any quick checks i can do. I checked the compression when i bought it about a year ago. all were even and above 100. i think it was about 120 across the board. I can recheck though. I have changed all my fuel lines, fuel pump, fuel filter on engine. I have not changed the fuel/water separator but i was told it was changed before i bought it. I just checked spark last week and i have spark on all 4 cylinders at idle. I run only non ethanol fuel since i bought it. I just went through the carbs about 3 months ago. I just don't want to invest money into a prop quite yet until i know the engine is running correctly. Some times the boat seems sluggish jumping up on plane as well. Link to comment Share on other sites More sharing options...
Brent B Posted May 18, 2016 Author Report Share Posted May 18, 2016 BTW Marcus thinks I should run a Power Tech PTR 3 blade 13.5 dia 17 pitch Link to comment Share on other sites More sharing options...
Lap it Up Posted May 19, 2016 Report Share Posted May 19, 2016 Marcus is normally spot on and that is the size I was thinking as well. Link to comment Share on other sites More sharing options...
trf97 Posted May 19, 2016 Report Share Posted May 19, 2016 It could be someone got that prop modified and there is nothing wrong with your motor. Only thing I would think you could do might be a card cleaning and run some concentrated seafoam through the motor. Link to comment Share on other sites More sharing options...
Brent B Posted May 19, 2016 Author Report Share Posted May 19, 2016 I run sea foam through the engine periodically. I just went through my carbs about 2-3 months ago. I only run ethanol free fuel. I'm gonna change my fuel water separator filter and make sure the throttle and timing are advancing like they should be fully. other than that I'm gonna get a separate fuel tank and primer ball and run the engine off that real quick and see what happens. If all seems the same then I'm gonna go ahead and buy the prop. The prop does kinda look like its been modified. I will look at it real close again when I get home. The boat is sometimes a little sluggish out of the hole which is another reason I think the prop is incorrect. The boat has run this way since I've had it. I got it about a year ago. The engine just runs to good. starts right up. plenty of power it just doesn't hit the numbers i would expect. Anyone local willing to let me try there prop? Link to comment Share on other sites More sharing options...
JEM Posted May 20, 2016 Report Share Posted May 20, 2016 Borrowing a prop is certainly your best and cheapest bet right now. If you cannot find a loaner prop to see if you can get the rpm's up, maybe you can take it into a shop for a dyno check just to confirm that your motor is not the problem. Your rpm's are definitely off and it's either the engine or prop, or both. (Unless Marcus is right wondering about the boat weight.) Link to comment Share on other sites More sharing options...
mulligan Posted May 20, 2016 Report Share Posted May 20, 2016 If you have a prop shop near you, you may want to have the prop checked. As said before just because it says "19"" does not mean it is 19. Out of the box they can be wrong or it might have been worked. As a plus if you do have a shop near you they might let you test props. On the down side if there is a shop near you you may stop in every week to try new props and you can go broke fast! I know I was glad/sad when the shop that was on my way home from work moved. Link to comment Share on other sites More sharing options...
Brent B Posted May 20, 2016 Author Report Share Posted May 20, 2016 Yes I do have a prop shop near by. In fact I have a couple. The one i have used before for my mercury 150 does not have loner props for engines that small. Which i think is BS but what can I do. How do you dyno a boat engine? i have never heard of this before. Anyways when I get back in town on Monday I'm gonna run a few test as mentioned above and then see what I come up with. I'm gonna try calling some of the other prop shops to see if they have loner props. Link to comment Share on other sites More sharing options...
JEM Posted May 20, 2016 Report Share Posted May 20, 2016 Most full service engine shops should have a dynamometer. Just call around to service shops for your Yamaha motor. Link to comment Share on other sites More sharing options...
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