Honda 90 mounting height on 22 foot cruiser

[Fred R. Stern]

Last spring I repowered my 1990 Cruiser with a Honda 90. It runs very well, but I seem to be throwing a rather large V-shaped roostertail that appears to be caused by the lead edge of the outboard, either cavitation plate,or the lead edge of housing. I have also installed a Doel fin because I had real good luck with one on my old 70 hp Johnson. The Honda is mounted as low as it can be on my transom. Is it too low? Has anyone had a similar prtoblem. It was bought and mounted at 3 Rivers marine in woodinville, and I am not too sure of their skill level with a C-Dory. Any and all advice would be greatly appreciated. My boat usually lives at 66 Rocky Pt., Brinnon, on Hood Canal, or on the trailer on River Road, up Duckabush Road.

 

[Rock-C]

Hi Fred
Welcome to the Pub. I also have a Honda 90. It is mounted about two inches above the lower most setting. (If that makes any sense). I talked to the local Honda dealer, Allan Marine in Salem, he said the cavitation plate should be even with the bottom of the hull. Sounds like yours might be a little low. Les at EQ would be the expert to ask. Give him some time and I'm sure he will chime in with the right answer.

 

[TyBoo]

Hi Fred -

Good to hear from you.

The last advice is the best rule of thumb we've heard. The cavitation, or anti-ventilation, plate should be even with the bottom of the hull at center. The Honda 75, with the same lower unit and bracket as your 90, that I had on my 22 had a good inch of clearance between the top edge of the transom and the bracket horseshoe.

It isn't a critical science, but if it is all the way down it is definitely too low and can cause the problems you noted. My A/V plate was about 3/4" lower than the bottom of the hull, and I raised it one hole so it was even. It didn't make much noticeable difference in performance changing it that small amount. I suspect, however, that you will see a dramatic difference both in WOT rpm and fuel economy if you raise it up. It will also get rid of the rooster tail.

Les has spoken in detail about this subject on other, short-lived, message boards. When he gets some time between building all the new CB boats, we'll set him to the task once again on here where it will be preserved for eternity.

So go hold a stick against the bottom of your boat and see where it hits the cavitation plate. Then look at the mounting bolts and see if you have enough holes and slot in the bracket to raise it up without drilling new holes through the transom.