Honda 90HP Low Power?

[Sandiford]

I have a 1999 Honda BF90 pushing a 17' Hurricane (approx. 1,300lbs empty, 2,000lbs loaded). The motor has a 15" pitch prop but still can't manage to get above 5,000rpm at WOT and performance seems a little sluggish. I am being blown into weeds by the same boats fitted with ten year old 75hp motors.<br /><br />I noticed that the Local boat dealer fits Yamaha 90HP motors with 17" pitch props to these hulls. <br /><br />Is there anything obvious that might be limiting my performance? I bought the boat last year and supposedly, the motor was fully serviced. It starts and runs great, with no misifres etc. Just seems to lack a little oomph. I have checked the obvious - Feul, filter, plugs etc.<br /><br />Any help would be appreciated.

 

[Hawaiian]

Re: Honda 90HP Low Power?

Check the throttle linkage to make sure the throttle is opening up all the way.

 

[ivar]

Re: Honda 90HP Low Power?

You can't usually compare prop pitches between different engines, due to different gear ratios and different max rpms. The Honda usually needs less pitch , to get rpms up to around 6000. <br />And IMO the honda's are smooth running , well built engines, but usually not as strong as the Yam/Mercs at the same HP. <br /><br />Could also be that the engine needs to be raised on the transom to get it to work properly. <br />Is the boat new or did you buy it used?

 

[Sandiford]

Re: Honda 90HP Low Power?

Perry, Yes, I did check the throttle linkage and it does seem to be opening all the way.<br /><br />Ivar, Yes, I did buy the boat used (from a reputable dealer)and the motor only has about 200hrs on it. What is the correct height setting for the motor? Visually, to me it looks about right, compared with other boats, but is there a more scientific method of measurement?<br /><br />FYI, the spark plugs look a little black - no carbon build up or sooty deposits, do you think a rich mixture could result in reduced performance, and is there an easy way to lean it up?

 

[MajBach]

Re: Honda 90HP Low Power?

Ivar: Honda's 90 final drive is 2.33:1 as opposed to a common standard of around 2:1. This means the 75 and 90 typically need coarser props.<br /><br />Wakey. I havethe same O/B on a 17' tin boat w/ 8' beam and semi-V hull. It weights about the same as your boat PLUS the weight of the motor - another 400 approx. Downhill and with a tailwind, I'm getting 5500 rpm with a 19' prop and about 40 mph. I also have two 17" props. The Mercury cupped prop goes about 5600 rpm and the Michigan prop about 5800 - all around the same speeds. I had a 15" prop that was neck-snapping acceleration and topped-out at 6200.<br /><br />IT is true about the throttle opening all the way and an easy check, but you need an extra set of hands to work the control box. Just watch the movement of the guide arm near where the throttle cable is exposed on the starboard side of the motor. When you look at it, you'll know what I'm speaking of and also know if it is opening all the way. The remedy is just as simple: there are tw pairs of set nuts ( for lack of a better word )that control cable movement or tension or whatever. You can fiddle around with them but be mindfull that you also may be changing where the motor idles. One other point to consider: how low does the motor sit on your transom? Mine is up two holes from extreme low.