Honwave T38 Transom height and motors

[ChrisParish]

I measured my mariner 9.9 and it is 17 inches to the plate.

Given that they are all 17 inches to the plate (give it take a smidge) then the problem is likely to be one of three things.
In what I feel is the most likely order
- shape of plate
- profile of prop blades
- profile of leg / lower unit.

I cranked the brightness and exposure on Stewy’s pic and it looks like you have quite a substantial plate with quite a bit sticking out from near the front.

Here is the plate on my Mariner:

Notice how it doesn’t really have any material to it until it gets an inch or so back from the front. My Mariner ventilates like crazy unless it is trimmed all the way in.

I also have a Johnson 9.9 which has no such problems and runs on the middle hole.
The plate on the Johnson is much more significant.

Here is a pic from the Suzuki Marine website. Notice how the plate is quite wide right from the front.

I hereby postulate that the issue is a function of plate profile and leg profile - with plate profile being the biggest contributor.

So - could please please post pics of their ventilation / cavitation plates please? I think we could be on to something.

[Stewy]

Dont have any other pics to hand,

The Suzuki seems to have the bigger and most square shape.

[chris moody]

Interestingly I tried a Suzuki 15hp on my Takacat and there was no trace of ventilation at all with a stainless uncupped prop.

[ChrisParish]

I am beginning to suspect it might be because of that mighty anti-ventilation plate.

[ChrisParish]

@chris moody, what does the AV plate on the Tohatsu look like?

-edit: just found a picture - it is quite different from the Suzuki.

[harrison]

I measured my mariner 9.9 and it is 17 inches to the plate.

Given that they are all 17 inches to the plate (give it take a smidge)

However @ChrisParish the new Mariner is a good half inch shorter at 16.25” which in my book will have a big affect if on the limit of working or not.

I agree the large AV plate on the Suzuki, particularly the generous width at the crucial leading edge, will give a big advantage on problematic hulls. In fact our Suzuki on the Aerotec suffered no splashing at all, which was a major problem on that particular hull. I’m sure the large AV plate on the Suzuki negated this.

The new Mariner has a similar AV plate profile to previous models, no real width until well back. Unlike the Suzuki.

Mariner 20 AV plate

Suzuki DF20 AV plate

So yes, the mega AV plate and extra leg length of the Suzuki makes it far more tolerant of ventilation on the T38.

It would be interesting to get some dims of the Honda motors. After all Honda only make inflatables to sell engines....so hopefully compatible.

I would be wary of recommending bolting the new Mariner on a T38 as it seems it has the shortest leg length of all. The T38 also probably has a slightly deeper transom than most. This reservation will also apply to the new Merc and Tohatsu clones.

[ChrisParish]

@harrison sorry, I must have miss-read your original measurement as I thought it said 16.75 (I’m mildly disnumerate so I often miss-read numbers). .75 of an inch is a massive difference!

I have scrounged up some aluminium plate so seeing as my AV plate already has holes in for a hydrofoil I will make some extensions and bolt them on to see how it effects the ventilation issue. It will take me a week or so to get it done around work, but I will keep you appraised of the results.

[ChrisParish]

Just back to leg length again, @harrison. My Mariner is 17 inches and is just as prone to ventilation as yours, if not worse as I have to trim it right in and your ran most of the day on the middle hole, however I fancy that your AV plate is wider than mine.

[Bigplumbs]

This has all caused me not to buy the 20 hp Tohatsu I had lined up.

When you are saying the new Mariner etc what year are you talking about ?

[ChrisParish]

The EFI ones with the angular hood, Late 2018 onwards, Bigplumbs.
Sorry to hear that you felt you had to cancel your Tohatsu. Were you going to buy a new one?