How big of motor can i go?

BassAssassin · Jun 8, 2009

I need more speed!! lol. 25mph not fast enough. Okay so here it is.... My boat is a Fisher Marine. Measure 15' x 60" X 48" floor. Transom height is 17". Placard says max 25hp, 800lb people, gear, motor. Now i know it can handle more motor. I had the same 25hp on my 1436 Ouachita, and had the little thing loaded with firewood, campgear, beer, bait and ammo and two of us and floated just fine. Now my current boat has been modded but sides are aluminum capped with 1.5" foam, i have 1.5 foam under the floor deck, entire length of boat. I was thinking maybe a 50hp. what do you all think. BTW my 25hp is 140lbs. I estimate that with standard gear, fuel, battery, troll motor, and me i have about 225lbs of stuff in the boat at all times.NOt including main motor. So here it goes.... fire away..

PS. it's plumbed and built for dual 6gal tanks

Loggerhead Mike · Jun 8, 2009

i wish my rig could handle a 140lb motor [-o<

BassAssassin · Jun 8, 2009

Loggerhead Mike said:
i wish my rig could handle a 140lb motor [-o<

Yup 140# is what i read somewheres on the net when researching the Merc. You have a link to view your rig?

crazymanme2 · Jun 8, 2009

From what I see on your pic you could raise the motor so the cavitation plate is even with the bottom.Just don't go too high, so the water intake is out of the water.You might be able to go a little more pitch also.I have a 11 pitch on an 1975 20hp Merc on a 12 footer vee & by myself I does just over 30mph gps.The weight your pushing doesn't seem like that much for a 25.You can gain alot on setup & the 25 will be better on gas.I think that the 50 will be too much weight unless you find an older 50hp Merc they weigh just alittle more than your 25.Just a thought

BassAssassin · Jun 8, 2009

how do i raise to motor w/o it looking goofy?

crazymanme2 · Jun 8, 2009

Your boat could run a short shaft motor,I think, if yours is a long which it looks like to me, but I could be wrong.
What pitch prop ya running?

ober51 · Jun 8, 2009

BassAssassin said:
how do i raise to motor w/o it looking goofy?

You could get a jack plate or build it up with some wood wrapped in aluminum. I am trying to do the latter. There are a few people here who have done this already.

BassAssassin · Jun 8, 2009

crazymanme2 said:
Your boat could run a short shaft motor,I think, if yours is a long which it looks like to me, but I could be wrong.
What pitch prop ya running?

it's a 13/p prop

BassAssassin · Jun 8, 2009

crazymanme2 said:
From what I see on your pic you could raise the motor so the cavitation plate is even with the bottom.Just don't go too high, so the water intake is out of the water.You might be able to go a little more pitch also.I have a 11 pitch on an 1975 20hp Merc on a 12 footer vee & by myself I does just over 30mph gps.The weight your pushing doesn't seem like that much for a 25.You can gain alot on setup & the 25 will be better on gas.I think that the 50 will be too much weight unless you find an older 50hp Merc they weigh just alittle more than your 25.Just a thought

Heres a thought... I lived in IL when i bought the motor, so it is jetted for low altitude 650ft... I am now at 4900ft. The motor does still start instantly and runs good and strong, but it seems like not at as high of RPM. My prop is not in pristine condition. It has some knicks and burs. Do you still think i should go with more pitch, or try changing to high altitude jets. I have also heard of instances where guys will carry a different prop for high altitude. BTW thanks for the info. Is the cavitation plate the horizontal plate immediatley above the prop?

Loggerhead Mike · Jun 9, 2009

Yup 140# is what i read somewheres on the net when researching the Merc. You have a link to view your rig?

not yet. my g/f's camera took a dump on us this winter but work is picking up slowly so hopefully i'll be able to get her a new camera in a month or so

CarlF · Jun 9, 2009

Is the cavitation plate the horizontal plate immediatley above the prop?

Yes, that is the cavitation plate, it should be even with the bottom of the hull.
Looks to me like you are running a long shaft on a short transom, which is part of any performanace problem you are having.

As far as how much HP, its rated for 25, so 25 is as high as you can go in many states without running into legal issue.
That aside, I would not go more than 30.

Nick Jones · Jun 9, 2009

I was going to say the same thing as CarlF. If you go larger than the boat allows/states and are visited by a wildlife officer you may regret it.

Just some advice.

ben2go · Jun 9, 2009

Hang a 150HP on there and out run everything.Can't get in trouble if they can't catch you. :LOL2:

BassAssassin · Jun 9, 2009

ben2go said:
Hang a 150HP on there and out run everything.Can't get in trouble if they can't catch you. :LOL2:

lol i like your thinking, but i have to put it back on the trailer sooner or later, and they'll be waiting.

ben2go · Jun 10, 2009

That's true.

redphysher · Jun 10, 2009

Bass:

Just the give you a heads up. I was going to put a 15 HP on my little boat that is rated for 10HP Max. I have a 9.9 now. On a 14 FT delhi jon. but my boat runs about 20 mph i guess. Your problem is very likely your long shaft/mid shaft motor as another poster has said.

As for the legality of it all. You will pay a hefty fine. My friend paid roughly 10 US per HP over he was running a 70 on a 50 rated boat. So he paid roughly 200 buck-a-roos.

What is boat speed anyway? You still get there. In one piece and you get to enjoy the scenery. Doing 60 MPH everything is a blur and your face wants to rip off. I cant tell you number of times I have been putting through the marsh and a 30,000 bay boat flies by passing up some of the best fishing holes I know of 600 yards from the ramp. Half the time I just troll over there enjoying the not having to work thing.

take a look at this site it should help explain:

https://www.smalloutboards.com/shaft.htm

BassAssassin · Jun 10, 2009

Thanks Red. That was very helpfull and informing. So how would be the best way to raise the transom and keep strength and integrity, without over building it? I am a carpenter by trade, so I am thinking 2x8 and some "L" StrongTies, 1/2" galv. carridge bolts? And should I also raise, and/or reinforce the transom diagnol brace? Also, look up my previous post in this thread about changing the carb jet vs. the prop pitch. cause my motor came from low elev. to higher. about 4200ft difference. Thanks all for your replys!

redphysher · Jun 11, 2009

Bass,

These two sites should help you even more:

Jackplate sold by basspro really cheap. I have never used it. This could be your quickest way to better performance.

https://www.basspro.com/webapp/wcs/stores/servlet/Product_10151_-1_10001_8782_225011002_225000000_225011000?cm_ven=bazaarvoice&cm_cat=RLP&cm_pla=8782&cm_ite=description_link

And a site about props. Enter your info on your boat and it recommends prop pitches, etc.

https://turningpointpropellers.com/

BassAssassin · Jun 11, 2009

Red, those are some very good links. Thanks

LarryA · Jun 11, 2009

No offense to anyone but why is it that Speed is so important to so many people? The faster you go, the faster things can go very wrong!

How big of motor can i go?

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