Honda outboard BF30A only goes 17mph...

I just got a new boat and I knew it was running slow and that I'd have to give it a tune up or take it somewhere but the engine only goes 17mph.. I know the boat weight factors in (17' fiberglass) but 17mph is a bit slow isn't it? Or is that normal for a 17'? my friend has a 17' aluminum boat which has to be lighter considering its just a single layer but his goes probably 25 or so. Just looking for some info. Thanks

My 15' fiberglass does 33 with just me and fuel with a 70hp motor. But this is a heavy Ranger bass boat, and and older 1977 outboard.

I have a hard time seeing much more than what you're currently seeing out of a 30hp on a 17' fiberglass boat. I'm actually kind of surprised it will plane out...but we know nothing about your boat other than it's 17' and fiberglass.

More information would help.(make/model/year) What pitch prop are you running? What are full throttle RPM's? This will help us decide if a different prop would help you.

what kind of rpm's are you getting at WOT ?
this will help determine if you have the right pitch/diameter prop.

if your rpm's are 5500 to 6000 at WOT.

then thats all u shes got captain

One important factor would be how you are able to trim the motor. If it is mounted to the hull correctly in the first place, with the cavitation plate approximately 1 to 3 inches BELOW the keel, having it then placed at the proper trim angle or "attitude" can make a huge difference in maximum speed. For example, I have a 16' FisherMarine aluminum semi v with a 50hp Mercury 2 stroke. I hole shot with the motor trimmed all the way in and then trim out several degrees when on plane. I have GPS clocked 42 mph on that little boat but if I don't trim, it slows down drastically.

Of course, load makes a big difference too.

It's just a guess but I think if you get all the above factors lined up ie: RPM in the mid 5k range, outboard properly hung on the transom, and good trim angle, it SHOULD get up in the 20's.

The one thing about most of the smaller outboards is that the power trims (if you have one) don't have enough oomph to trim the motor out when on plane. I use an electric powered tilt with gears and it works great. It moves much slower than the hydraulic trims but is VERY powerful.

Jimmy - Point of inquiry here - I've always been told, and have always practiced, that the cavitation plate should be even with the lowest point on the keel at the transom when motor is mounted directly to the transom. If you have an extension mount, then raise the cavitation plate one inch above the lowest keel point for every 1 foot of offset. As a final test, at WOT on plane, cavitation plate should be running right on top of the water coming off the bottom of the transom.

Am I wrong on that issue?

You are correct and I am technically wrong.

I was just going by what I've done before on smaller boats and outboards and what has worked for me. I don't think a couple of inches deeper makes a big difference in speed but I know from tinkering that having the plate a couple of inches lower has helped me solve hole shot problems when the hull wants to "wallow" coming up on plane.

In this case, I was actually wondering if he IS having a hull planing issue and that it may be, at least partially, what is keeping his speed down.

my - No problem - thought I might have gotten it wrong along the way.

Taymag - give us some more info and we will try to help - weight of boat, type of boat, type of prop. The key issue is, as Dark_Star posted, is whether you are getting at least 5500 rpm's at wide open throttle (WOT?) If you are, then, it's a case of playing with your mounting height, trim, and prop.