Opinions on motor change?

[Redbelly]

After looking around and a little thought I want to repower my vessel.

But I only want to go up 10 hp, and this is due to the weight factor. Also I would be changing to 2 stroke going from 40hp 4s to 50hp 2s. Weight of the motors is the same.

With the tunnel hull I expect a much better hole shot, and top end, but a 30% loss of gas mileage.

What is a poor fisherman to do??

[birddog]

That'll work.

[Barhopr]

How much more gas can a small 40 or 50 2 banger really burn over a 4 stroke. Is it enough to really add up? Not for me. If I fish all day I may only run my motor 30min more or less all day. I usually cover an average of around 27-30 miles. Most of that is under TM power. I spend more on Ice than I do gas. Now if I had a boat that required more Hp then maybe but for small boats the weight and the lack of hole shot made me go to 2 stroke. .02

[birddog]

I doubt he's worried about the gas as much as he's wishing he had a better hole shot and top end speed. I know that was the thing I disliked most about my old boat. The 40 merc I had got the job done, but had no power. By myself it was O.K. but put Chalk and his gear in the boat and that 40 was a dog.

[tin can]

put Chalk and his gear in the boat and that 40 was a dog.

My boat is a dog with Chalk and ALL his stuff.

[birddog]

put Chalk and his gear in the boat and that 40 was a dog.

My boat is a dog with Chalk and ALL his stuff.

[Barhopr]

Amen brother

[Chalk]

By myself it was O.K. but put Chalk and his gear in the boat and that 40 was a dog.

You should try losing some weight, that will compensate for my tackle.

My boat is a dog with Chalk and ALL his stuff.

Stuff it, man with no paddle in his boat

Amen brother

Shush it, Mulch man (BTW I got sweet TFO rod case for $17 at Bluewater )

With the tunnel hull I expect a much better hole shot, and top end, but a 30% loss of gas mileage.

Let's dissect what you said:

You expect a better hole shot from a tunnel hull...The hole shot is based off the proper setup of the motor (height) and prop (running the correct RPMS) You stated in other posts that you weren't sure of the RPMs you were running. I would not go through the trouble of changing motors until I spent a little time doing some proper boat setup. Based off the information of motor weighing the same and only 10 more HP, doing some prop work would be the best money spent...If you find out you are running the correct RPMs, then you can start paying with adding more cup, raising the motor, doing this and doing that...What research I have done on boats and boat design, tunnel hull design has always been a mysterious concept to designers...I have read that they are really inefficient, can cause problems with hole shot (the tunnel removes a vital area of displacement at a key area on the planing surface of the hull, which can cause hole shot issues)...But two of many skinny water dream boats are tunnel hulls, if setup right, they can take you places you might not want to go...In my humble opinion play with the prop before going to the expense of motor swapping.

[Redbelly]

Again Chalk, the voice of reason and intelligence concerning boating knowledge.
You perceive my dilema correctly, as in a better hole shot. A little more top end would be nice, but how much would I really gain with 10hp?

I have to wait for my mechanic to recalibrate his portable rpm gauge, unless someone knows where I can go to find out my rpms.

Perhaps the 4 blade will solve my kiniption. I would be happy with a 50% increase in lift out of the hole.
As for lifting the motor I have a HLP, and T&T. I have found that motor position does indeed affect hole shot lift.

I basically got this boat because of the great deal. I was never looking for a tunnel hull. And where I fish the most I ain't too keen on WOT no matter how skinny a boat it is!

[tin can]

Redbelly, your hole shot, and , maybe, a little bit more top end can be achieved with the right prop, and possibly some prop modification. After you find out what RPM you're turning now, I'll give you the name and phone number of a gentleman that does custom prop work. He got me a great hole shot, and 7 mph of top end (on the bass boat).

[Redbelly]

Thanks tincan, just as soon as I can accomplish finding out what the nasty little rpms are, I'll give you a shout, and thanks very much to everyone for your unput!

[birdman]

Why u want to change your engine? I thought that 40/4 cycle was the thing for power and efficiency?

[Barhopr]

Amen brother

Shush it, Mulch man (BTW I got sweet TFO rod case for $17 at Bluewater )

Hey, what about me. I got a phone, you could have called. I'm good for the $17 till the next time I see you.

[What a mess]

There is an article in Fla Sportsman about it. I don't think you will get enough difference to justify the cost. If you have money to burn change boats.

[T Smith]

I think Chalks right on about the mysteriousness of tunnel hulls. I've never got mine quite right and am still tinkering around with ideas of 4-blade props and even doing a little fiberglass work to extend the tunnel a little closer to the motor. I saw a picture of the new Sterling and the motor sits up in a pocket with the tunnel extending closer to the prop.

I'm having issues with the prop washing out at full throttle, like the water is too dirty. I think the tunnel makes the boat squat a little and makes the hole shot suffer but once you get up and running the beauty of the tunnel takes over and you can run in spit.

Theres also some websites from Texas and Louisiana that have more info on tunnel hulls. Those boys over there seem to love tunnel hulls. Heres a link to a company that makes a cavitation plate that may help, its designed to channel water around the prop after coming through a tunnel as opposed to the other plates such as a Bobs which I am running.

http://www.boatrightmarine.com/