I just re-powered a center console with a new Honda BF225. I noticed during the break-in period that while on plane there is a great deal of spray that fans out (and upward) from both sides of the outboard at the transom...so much that it could probably soak the people on the transom bench seat. It goes away slowly when you trim the engine up but I feel like I shouldn't have to trim the engine up. The old o/b (a Merc 225) did not do that in any position. It is the same length shaft (30"). I was wondering if the engine should be mounted slightly higher (or lower)on the mount. Anyone ever seen this before?
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fan of spray from o/b at transom when trim down
- Thread starter Kehaar
- Start date
On most production boats its recommended that the anti cavitation plate should be parallel to the boat bottom. I would look there first. while the shafts are same length ,maybe there is a slight difference in your honda compared to the merc. I bet the spray is coming off the plate. The boat might be sitting different now too. i am just guessing but if your merc was a 2 stroke it was a lot lighter than a 4 stroke honda. If the merc rode with the plate just out of the water is it possibe that the additional weight of the honda causes the plate to just hit the water and cause the spray?
Interesting analysis. Yes the Merc was a 1995 2 cycle and of course the Honda is a 4. If that explanation is true, I wonder how to correct it. Funny thing is I saw another boat yesterday doing that same thing. It too had a Honda, but couldn't tell how old the boat was (don't know if repowered)
Tommy Allen
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The answers above are totally correct. BUT, one thing not mentioned, you may be undertrimming the boat (going too far down and under the boat). You might look at the pin placement on the motor to see how much negative trim you are getting. Raising the pin by one hole could eliminate the problem also.
"raising the pin". Can you elaborate on the pin? I thought I would have to get the dealer to unbolt from the transom and raise the motor by bolting through the hole below the existing one in use on the mount. By the way the ventilation plate is just slightly below the lowest center point on the transom when the motor is trimmed all the way down. Maybe quarter inch+/- below. Thanks.
Tommy Allen
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The "pin" goes between the motor bracket. The "pin" stops the motor from trimming below a certain level. Before power trim became standard equipment on most larger motors, the "pin" was used to set the trim on the boat. Most can be adjusted with no tools. I have seen on larger outboards where it could be more difficult to adjust. The pin stops the downward trim at a set level.
If the "anti-ventilation plate" is even 1/4 in. below the hull, it's too low. Get the dealer to raise the motor one hole. It will ride better, perform better and burn less gas. That will probably place the cav plate, see above for correct and never used name, about 1/2 in above the bottom and really help the boat performance at all speeds.
Tommy Allen
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I looked it up!! In one article, anti-cavitation and ventilation were used interchangeably. The article also stated on a fiberglas boat that the motor could be up to 3/4 of an inch above the bottom of the V. I've never seen that in print before, but I have run motors that high.
Zane may well be correct about a prop change being in order. One particular boat that I had growing up was a 15 1/2 foot ski boat with a 115 Evinrude. It chine walked really bad. I raised the motor by one mounting hole and it all but eliminated the problem. I was running a stainless steel prop that was cupped. I put an aluminum prop on it one day and it would peg the tag at the hit of the throttle with the aluminum prop. I would guess about 80% prop slippage.
Good luck.
Zane may well be correct about a prop change being in order. One particular boat that I had growing up was a 15 1/2 foot ski boat with a 115 Evinrude. It chine walked really bad. I raised the motor by one mounting hole and it all but eliminated the problem. I was running a stainless steel prop that was cupped. I put an aluminum prop on it one day and it would peg the tag at the hit of the throttle with the aluminum prop. I would guess about 80% prop slippage.
Good luck.
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The "correct term" is "anti-ventilation plate".
Ventilation occurs when the prop sucks up air, particularly air from the surface.
Cavitation occurs when, due to local low pressure on the face of the prop, a small bubble forms. ( ie: a small cavity i the water )
The plate actually does little to cause or prevent cavitation. It does, however help prevent a nearly surfaced prop from sucking air in from above the surface. ( ie: it does prevent ventilation )
That said, folks have been calling it an anti-cavitation plate for decades, even though it is a misnomer.
Ventilation occurs when the prop sucks up air, particularly air from the surface.
Cavitation occurs when, due to local low pressure on the face of the prop, a small bubble forms. ( ie: a small cavity i the water )
The plate actually does little to cause or prevent cavitation. It does, however help prevent a nearly surfaced prop from sucking air in from above the surface. ( ie: it does prevent ventilation )
That said, folks have been calling it an anti-cavitation plate for decades, even though it is a misnomer.