boat motor ratings??????????

tvpear12

Petty Officer 2nd Class
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Aug 25, 2004
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I have a Tournament TF1600 that is rated for a 115 horse. I have a 90 horse on it now but would like more power as the 90 horse is under powered. does lake potrol check this close or very often? would like to put a 150 hp on but dont want to get my boat impounded. does any one know a way around this uncalled for boat rating. I like the rig overall and do not really want to sell it but would like a larger moto. I know changing the stickers/decals out will not work as the cowling is so much larger on a 150 hp because it is a v6. any help would be great.<br /><br />PS. I AM NOT AN OUTLAW SO PLEASE DO NOT GET THE WRONG SIGNAL HERE.
 

WillyBWright

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Re: boat motor ratings??????????

There are plenty of reasons not to put a V-6 on that boat. One is transom strength. Will it be able to take it??? It wasn't constructed with a V-6's weight and torque in mind.
 

tvpear12

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Re: boat motor ratings??????????

Thank you Leiutenant Wright.
 

Chinewalker

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Re: boat motor ratings??????????

If 90 is underpowered and you're rated for 115, why not find a 115? That's a 25hp increase, approximately 20% if you want to look at it that way. It's not insigificant and may be the ticket....<br />- Scott
 

walleyehed

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Re: boat motor ratings??????????

My thoughts are that if it's rated for a 115, and is "Underpowered" with a 90, there are other issues involved.<br />There is a difference between 90 and 115, but not enough to get what you are looking for by stating "underpowered with a 90"<br />I've been down this road, replaced a 90 with a 115 and turned the same prop 100-150 RPM more-not the upgrade I was looking for either....then stepped in a gent on this board that walked me through some technical set-up of the 115, and found alot of hidden performance that could of been had with the 90 as well.<br />It's not always the number on the hood that provides the answer.
 

steelespike

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Apr 26, 2002
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Re: boat motor ratings??????????

Motor trim is important.Anti vent plate(anti cavitation)should be about even with the bottom of the boat then raise the motor virtically about 1/4 inch at a time until just before ventilation becomes a problem.As little as an inch up can give as much as 3 mph.Be sure to keep<br /> as much weight out of the stern as possible.<br /> Motor trim angle should start paralell with the bottom and then be adjusted for best performance.<br /> If no power trim set the trim in for more hole shot for skiing etc.Once you have the trim all set then maybe a prop is in order.Depending on the present rpm, speaking basically less pitch will give better hole shot and power.More pitch gives less hole shot less power and possibly more top end.Kind of like overdrive.Of course a good tune up by a reliable shop might help too.
 

ZmOz

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Re: boat motor ratings??????????

Depends on the age of your motor. Sometime in the early 80s they went from crank rated HP to prop rated. That means a 1980 115hp motor will be alot slower than a 1985 115hp. Also, alot of outboards use the same block/LU for many different HP ratings. On a Mercury inline 6, for example, you could put the cowling from a 90hp on a 150hp and nobody would ever know it's a 150... ;) <br /><br />As for whether you should or shouldn't over power your boat, nobody here should be making that judgement for you. If you use a little common sense, and don't put a 300hp on a 10' inflateable, you should be fine. Just make sure your transom is in good condition and stays that way after a larger motor is installed. Also don't do stupid things like turn as hard as you can at full speed...
 

walleyehed

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Re: boat motor ratings??????????

By ZmOz;
That means a 1980 115hp motor will be alot slower than a 1985 115hp.
Actually ZmOz, there is only about 100-150 RPM difference in the case of these V4's (Crossflows),If that...the difference really came in 1995 with the 60 deg. V4, so if replacing a pre 1985 115 with a 1995 Looper(they made the crossflow thru 1998)in 115HP, the difference is quite greater.<br />I went from a 1979 115 to a 1997 115(Both X-Flows)and was very dissapointed in performance gain. When I went from a 70 tripple to the 90, there was some gain-a little performance and a bit more fuel. the 1983 90 back to a 4 yr older 115 provided about 100 RPM gain, but I had to work to get that much, and the 1997 115 (set-up the same) provided little gain until I added some set-back and lift, then the numbers got alot better.<br />I sold the 97 115 and now have a V6 in the 200HP range, and will be the first to admit, it takes a TON more HP to enhance the performance from what one would think. My point is don't add a V6 to a boat designed for a V4 or 115-125 max because the next 50HP just makes up for the weight gain before any real performance gain is noticed...Maximize what you have first, then take a look at what may be the next step in a performance up-grade.
 

ZmOz

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Re: boat motor ratings??????????

Originally posted by walleyehed:<br /> By ZmOz;
That means a 1980 115hp motor will be alot slower than a 1985 115hp.
Actually ZmOz, there is only about 100-150 RPM difference in the case of these V4's (Crossflows),If that...the difference really came in 1995 with the 60 deg. V4, so if replacing a pre 1985 115 with a 1995 Looper(they made the crossflow thru 1998)in 115HP, the difference is quite greater.<br />I went from a 1979 115 to a 1997 115(Both X-Flows)and was very dissapointed in performance gain. When I went from a 70 tripple to the 90, there was some gain-a little performance and a bit more fuel. the 1983 90 back to a 4 yr older 115 provided about 100 RPM gain, but I had to work to get that much, and the 1997 115 (set-up the same) provided little gain until I added some set-back and lift, then the numbers got alot better.<br />I sold the 97 115 and now have a V6 in the 200HP range, and will be the first to admit, it takes a TON more HP to enhance the performance from what one would think. My point is don't add a V6 to a boat designed for a V4 or 115-125 max because the next 50HP just makes up for the weight gain before any real performance gain is noticed...Maximize what you have first, then take a look at what may be the next step in a performance up-grade.
Depends on the motor I guess. Again, using an inline 6 as an example, A 1980 150hp is exactly the same in every way as a 1985 115hp. If you took a boat that was rated for 115hp max, and had a 1980 115hp on it, you would see a significant difference if you changed over to a 1985 115hp. It would also be perfectly legal in every way....
 

walleyehed

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Re: boat motor ratings??????????

Legal, yes....significant difference, no.<br />The 2 115's are only about 10HP apart at the prop, it takes 15-18HP at this size to actually increase 1 mph. They will both use the same prop, unless gearcase ratios are different, which I can't say on the merc.<br />He isn't specifically stating OMC, but in his sig., I assume that's what he's refering to.<br />In the OMC products, the 2 115's are not far enough apart to make a noticable difference.<br />If the 90HP in question is pre 1985 and replacing with a 115 Looper, yes, there will be some difference, but not night and day.<br />If it's underpowered with the 90, the 115 would barely if at all, "Fix" the problem.<br />I believe the first item I would look into is the health of the 90...If it's good, I'd start with working the set-up, as I can't believe it's underpowered, in fact, I know it's not.<br />tvpear12, need to check that engine out and make sure it's all up to par. How is it mounted...directly to transom? Jackplate? What prop are you using and what max RPM are you getting? Let's see if we can find the core issue as to why you consider it underpowered.
 

ZmOz

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Re: boat motor ratings??????????

Originally posted by walleyehed:<br /><br />If it's underpowered with the 90, the 115 would barely if at all, "Fix" the problem.
Again...if the 90hp is crank rated and it's replaced with a prop rated 115hp, that is a significant difference - aproximately 60hp. I don't know about the OMCs, but I can tell you without a doubt going from a 90hp crank rated inline 6 to a 115hp prop rated would definately be a night and day difference, but neither of us know which motor he has or plans on using, so there's no point in arguing about this.
 

walleyehed

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Re: boat motor ratings??????????

There is LESS THAN 10% difference in crank vs. prop-shaft rating. I'm not sure where you are getting your information but it is incorrect.<br />There is no argument here, but I don't think you're understanding how they were vs. are rated.<br />The 2 mentioned above by you are only 25HP apart give or take 10%, and as I said, at these ratings, regaurdless of where it is taken, it still requires about 15-18 HP to gain 1 mph.<br />The 2 engines are the exact block, porting and all. You don't get 60HP out of a set of carbs.<br />Now, as I said before, we need to establish how tvpear is set up now. when we see how that is, we can make recommendations from there.
 

ZmOz

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Re: boat motor ratings??????????

Again, I was talking about Mercury inline 6's. Whenever the change was made, the 150hp was renamed the 115hp. That means the difference between a crank rated 90 and a prop rated 115 is 60hp. (exactly the same as the difference between a prop rated 90 and a prop rated 150) Like I said, I don't know about OMCs, but even if they were both prop rated, going from 90 to 115 is a difference of 25hp. If you go from a crank rated 90 to a prop rated 115 the difference is even bigger. And if he slightly overpowers his boat with a prop rated 120, 135, or 150hp, then there will be a HUGE difference from the 90.
 

walleyehed

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Re: boat motor ratings??????????

If you go from a crank rated 90 to a prop rated 115 the difference is even bigger.
I did just this, and I'm telling you now(again), it does not improve performance at any significant level.....2mph at best.<br />The 150 I6 Merc was not simply "Renamed" a 115.<br />The port-timming was changed, the carbs and intake are both different as well.<br />Please, let's try and obtain some other info on his set-up and I think we will find the problem.
 

ZmOz

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Re: boat motor ratings??????????

Originally posted by walleyehed:<br /> I did just this, and I'm telling you now(again), it does not improve performance at any significant level.....2mph at best.<br />
Like I said...it depends on the motor. Maybe the motors you used weren't that different...some are. I will bet you my boat that there is a significant performance difference between a 90 crank rated I6 and a 115hp prop rated I6. WAY more than 2mph.<br /><br />I have heard from several people who have the same boat as me, only with a 115 (crank) I6. They top out at around 40, while my 150 (crank) I6 tops out at 50, closer to 55 with a better prop. That's 10-15mph from 35hp. I imagine a crank rated 90 on my boat would do about 35mph. (That's a 20mph difference when going from a crank rated 90 to a prop rated 115)
 

walleyehed

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Re: boat motor ratings??????????

I'm glad it works out with your application. :) <br />Now let's see if we can help tvpear with his application.
 

JB

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Re: boat motor ratings??????????

Ahoy, tvpear12.<br /><br />You need to define what "underpowered" means to you. <br /><br />You need to tell us the model number of the JohnnyRude 90 you have on your boat that is rated for 115hp, max. What rpm is your engine making at WOT?<br /><br /><br />Don't get hung up in HP numbers or crank vs. prop rating. When it comes to real, on-the-water performance it is cubic inches and rpm that count most. Hp numbers are for marketing.<br /><br />A JohnnyRude 90 in good tune and correctly set up should push your boat to within 2-3mph of what a 115 of the same series in good tune, etc. can do.<br /><br />If you and I should agree on what "underpowered" means, then I suspect that you have a sick engine or one that needs a lot of fine tuning of the set up.<br /><br />Going to a 115 wont give you a return even close to the cost and going to a V6 would be a very bad idea.<br /><br />Let us know, and good luck. :)
 

Solittle

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Re: boat motor ratings??????????

tvpear12 - I'm sure that you know that if you have a major accident that your insurance company will probably deny your claim if you have a motor larger than the max specified by the manufacturer. That would make lawyers very happy and they like that.
 

tvpear12

Petty Officer 2nd Class
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Aug 25, 2004
Messages
130
Re: boat motor ratings??????????

ok guys, its a 1989 v-4 crossflow rebuilt 4 months ago. new pistons, rod b, main b,rings, all new gaskets and seals. no carb work done as it fires and hits on all 4 cyl. engine atually runs well but after reviewing rpm threads here on iboats, things do not appear as so good now. rpms are 4800 by my tach, which is the factory tracker marines tach. maybe it is wrong.transom mounted speedo shows 46 mph. it may be wrong also. by underpowered i mean that for a 16 foot fiberglass tracker seems as though it should run closer to 50 mph at maybe 5500 rpms. if i am mistaken by this concept please feel more than free to advise.I have this puppy bolted to a jack plate. vent plate is 1" above the bottom of the hull. the hull is a step type hull. fully trimmed, wot, this engine will grab air if i move the engine up any higher, as its only a 20" shaft and think it needs to be a 25" shaft. i instant messaged dhadley about maybe getting a 4 blade prop that it might help and he has advised me on a couple of things to go over. such as timing,rpms,and mph.He seems to think the boat is turning more rpms than it says it is. he also thinks that a 4blade prop will help me to raise the engine. prop that im running now is 13&3/4x 19. any thoughts will be respected in the upmost. Thanks, Ted
 

walleyehed

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Re: boat motor ratings??????????

WOW!!!! a double post from JB......Gotta be a first. :D <br />He must really be....human, then... :)
 
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