Can my motor be raised?

[XcellR8]

Re: Can my motor be raised?

Originally posted by CoolMaker:<br /> Go to the parts on here (IBoats) look up trim tabs, then look at the pics of them. Part # 18-6014 is set back and will require no cutting to let the prop have clearance. <br />Note: Any boat dealer that would tell you to cut out a trim tab for clearance, surely does not know much and I would stay as far away from him as possible!!!!!!

Thanks, what page did you find that part number on (I must be blind, the closest number to that was 18-6011 on page 2)?

 

[Coolmaker]

Re: Can my motor be raised?

Go to trim tabs, page two (2), then click on the picture to the left. It will pop up a new window, then you will see the three (3) parts numbers and the differences. :

 

[XcellR8]

Re: Can my motor be raised?

Originally posted by CoolMaker:<br /> Go to trim tabs, page two (2), then click on the picture to the left. It will pop up a new window, then you will see the three (3) parts numbers and the differences. :

Found it now. What is the one on page one for (Part # 822777Q1)?

 

[XcellR8]

Re: Can my motor be raised?

Originally posted by XcellR8:<br />

Originally posted by Stillfishing:<br /> Guess you answered my question!<br /><br />Your favorite prop so far seems to be the 13x19 alu. With your other symptoms, you're wise to think of motor height next. Check the position of the AV plate relative to your keel - most boats need it to be level with or slightly above keel level at stern.<br /><br />As there's plenty of scope to raise the motor, and as some of the symptoms you've described are often cured by doing it, then why not use a plate as SoLittle suggests, and go ahead and experiment.<br /><br />Watch for prop ventilation and motor water pressure issues as you do it. Keep a record of speed and WOT with each change.<br /><br />The torque-steer you mentioned could have something to do with a low motor, but check the position of the trimfin below the AV plate. Maybe by adjusting this you can minimise torque-steer (swing the trailing edge right to counteract a starboard-steering boat, and vise versa).<br /><br />Post back results huh?

I haven't tried rasing my motor yet but I had the chance to try two more props, a 13.25 x 17p alum. Merc prop and a 13 x 17p K-2 black SS Yamaha prop. <br /><br />The Merc prop performed similiar to the 13 x 19p Merc prop but it was a bit more revvy near the top and it made the nose ride a bit higher when cruising at non-planing speeds. It gets up to 30 mph pretty quick but the speedo climbs noticeably slower after that. Top speed was 41-42 mph @ 5400 rpm so it's running where I was told it should be but it appears to be a bit slower in the midrange and top end (two people in the boat as with all other testing except the buddy with me this time is about 50 lbs heavier than my brother who was with me when I got 43 mph @ 5200 rpm with the 19 pitch).<br /><br />When I tried the 13 x 17p SS Yamaha prop the first things I noticed was that the nose rode a lot lower when cruisng at non-planing speeds and that most of my torque steer was gone (I was quiet amazed at how much easier I could turn left regardless of trim position, I really like that). The boat still has a tendency to porpoise if you get carried away with the trim but it seems to come out of it a bit better if you catch it in time (otherwise you have to really back off the throttle to get it to stop).<br /><br />The prop seemed to perform real well at most speeds but like with the 17 pitch Merc prop it was a slower climb after 30 mph (from 35 mph and up it's probably the slowest of the three, it almost felt like it could use a bit more gear but it wouldn't over rev until you held it WOT and bumped the trim up until it got close to porpoising). Top speed was 40-41 mph at 5600-5700 rpm which is a bit on the high side (with the same buddy in the boat).Cruising at 30 mph the Yamaha prop revs at 4600 rpm compared to 4000 rpm with the 19 pitch Merc (I forgot to check the 30 mph rpms with the 17 pitch Merc prop). Now it's got me wondering what a 19 pitch SS Yamaha prop would do or even a regular alumin. 17 or 19 pitch Yamaha prop (I'm not sure if my motor has enough power to really benefit from a SS prop). <br /><br />I plan to do a bit more testing with more people in the boat to see how much that effects WOT rpms. From a handling and driveability point of view the Yamaha wins hands down but I think the motor needs to be loaded a bit more at the top. It also seems like both aluminum Merc props may benefit form raising the motor but the Yamaha one may not.

Tried the 13 x 17p SS Yamaha prop again with two people and it ran 40 mph @ 5600 rpm. It hits a bit of a wall at 35 mph until you trim up some more and then it slowly climbs up another 5 mph. Ran it with four adults and got 38 mph @ 5600 rpm (I would have expected my rpms to drop with two more in the boat, almost like it's not getting loaded down enough on the top). The boat planes pretty easy with both gas tanks and two people in the back. As soon as it's on plane it shoots up to 30 mph quickly but the last 10 mph come pretty slow, almost like it's running out of gear. <br /><br />With the 19 pitch Merc prop I tried it still had decent acceleration after 30 mph and would top out at 43 mph, 5200 rpm (the last 5 mph takes a while). Even though this is a couple hundred rpm lower than I was told to run it the top end is better along with the fuel milegae (the spec is 5000 to 5500 rpm). This makes me think I may be better of with a 19 pitch Yamaha prop especially if I end up raisng the motor (whether it be alum. or SS).<br /><br />Does any one know if the Yamaha aluminum props perform similiar to the Black steel ones? By that I'm referring to how much it improved the over all driveability and reduced the torque steer on my boat compared to the Merc 13 x 19p & 13.25 x 17p alum. props I tried (I can actually drive it with one hand on the wheel and the other on the throttle when I'm navigating the the windy creek I drive down to get to the river).

 

[XcellR8]

Re: Can my motor be raised?

I tried a 13 x 19p SS Yamaha prop and it performed better than the Merc 13 x19p Alum. but it didn't improve the handling and reduce the torque steer's as much as the 13 x 17p SS Yamaha one. For this reason and the fact that the 17 pitch would be better with more people in the boat or pulling a tube etc. I decided to stick with that one.<br /><br />Thanks to all who helped me out with my questions, your input was appreciated!<br /> <br />For those interested in the results here they are in order of preference (boat is a 1990 Thunder Craft 15-1/2' F/G open bow w a 91' 90 hp Merc, spec says 5000-5500 rpm @WOT):<br /><br />2 people 4 people 6 people<br /><br /> #1 Yamaha SS 13x17p 3-blade: <br /> 2 people, 40-41 mph, WOT 5600-5700 rpm, 4 people, 38 mph, WOT 5600 rpm, 6 people, 37 mph, WOT 5400-5500<br /><br /> #2 Yamaha SS 13x19p 3-blade: <br /> 2 people, 41-42 mph, WOT 5200-5300 rpm, 4 people, 39 mph, WOT 5200 rpm<br /> <br /> #3 Merc Alum. 13x19p 3-blade: <br /> 2 people, 42-43 mph, WOT 5200 rpm, 4 people, 40 mph, WOT 5100 rpm<br /><br /> #4 Merc Alum. 13.25x17p 3-blade: <br /> 2 people, 41-42 mph, WOT 5400 rpm<br /> <br /> #5 Laser II SS 13.25x20p 3-blade: <br /> 2 people, 44 mph, WOT 5300 rpm<br /><br /> #6 Trophy Plus SS 13.75x21p 4-blade (the one that came with the boat):<br /> 2 people, 39 mph, WOT 4400 rpm