Top End Speed Problem

[CATransplant]

Re: Top End Speed Problem

Yup. Small boats with small engines are touchy about stuff. The OP here has a boat rated for 35hp, and has a 15hp on it. Getting it to plane and get a good speed is going to require careful attention to everything, and every difference in weight aboard will change things around.

I'd love to have a 9.9 on my little tinny, but I got that 1992 6hp for free from my father, who didn't need it any longer. Never one to look a gift horse in the mouth, I'm going to stick with it, and it's a sweet runner. I spent the early part of the season experimenting with weight distribution and trim to optimize the limited power when it's just me and my junk in the boat. On the rare occasions when I have a passenger (usually some kid who weighs about 100 lb.) I just settle for the slower speed, but trim out one hole to get the bow a little higher.

I spend most of my time on the lake with the outboard in the shallow-water running position, anyhow, so the planing stuff is just to get from one end of the lake to the other. Half the time, I end up trolling up and down the lake, anyhow, hunting for new honey holes.

 

[NSBCraig]

Re: Top End Speed Problem

If your spinning to many rpm's your prop is to wrong.

That's why I'm saying start at the beginning. You changed your prop as a maybe guess fix without know if it was the right thing to do when it wasn't the biggest problem (if you can get what I'm saying). The problem was wrong length motor for transom.

Now that you have you motor at about the right height and you got rid of the fin your spinning to many rpm's that means you are not running the right prop.

Everything else that you do is trying to adjust for the wrong prop.

Maybe some other guys could tell you how to dial a boat in with the wrong prop, I wouldn't have a clue where to start and kind of doubt anyone else can.

Also since you don't have a trim motor you have to decide on a compromise between holeshot and high end. If your not getting on plane quickly and your motor is trimmed out (which it is) then that is most likely the problem. Your trimmed for top end speed at for getting out of the hole.

There is no real easy answer on a compromise.

What would help make this compromise easier? Smart Tabs (which you'll still have to drop the motor down to level/ inline with the hull to tune, which continues to make me say do it now and go from there) and the right prop.

Make any sense?

 

[Crestliner2007]

Re: Top End Speed Problem

CATransplant - Boat set-up: Series 27 D.C. Battery in the bow, forward of the bow seat. Starting battery just forward of mid-ship seat. Gas tank (6-gal.) just forward of my back seat and on the port side. My tackle box (36#) on the starboard side. (If you'd like, I can send a picture.) I had the batteries positioned so that the weight would be distributed forward - as much as possible - when I run solo. They are hard wired thru the floor, so they cannot be moved. Originally had the gas tank right under the engine, but I moved it forward to give me more leg room. In testing my WOT speed, I've had my partner move back toward me each time, as well as move up and sit on the very bow. His position didn't seem to affect the top end speed, as much as the trim holes did. I only have 4 trim holes on the engine bracket.

NSBCraig - I'm re-thinking what you are saying here....maybe I will invest in another prop. That way I would have a second for back-up, as well as putting to bed the pitch theory.

I really do appreciate all your suggestions and guidance here folks. THANKS!

 

[NSBCraig]

Re: Top End Speed Problem

Bob's sells transom shims that you can use between your motor and bracket to get more trim adjustment.

Or maybe you could do something like them.

 

[CATransplant]

Re: Top End Speed Problem

Sounds like your weight distribution is fine. That's a lot how mine is set up, too. It just might be that that 11" pitch prop will do the trick, now that your outboard is up and out a little. Like you said, a spare is good to have.

If cost is the issue, look on ebay. Folks are selling props there all the time.

 

[Crestliner2007]

Re: Top End Speed Problem

Sounds like your weight distribution is fine. That's a lot how mine is set up, too. It just might be that that 11" pitch prop will do the trick, now that your outboard is up and out a little. Like you said, a spare is good to have.

If cost is the issue, look on ebay. Folks are selling props there all the time.

Thanks CAT! I'll look at ebay. Being retired and on a limited budget, this might be the answer I was looking for. I really appreciate you folks taking the time to help me out here. Great forum!