1992 15-foot Unknown Hull SUZUKI DF60a

[Nauti Native]

[This post is seeking advice about a propeller for a] 1992 15-foot hull [of unspecified original model that is only described as being] modified [and powered by a] 2013 SUZUKI DF60a [engine mounted in a position that is ambiguously described with the confusing description] second-lowest hole setting. [The anti-ventilation plate] is 0.625-inches [below the hull bottom].


PLEASE READ THE ARTICLE ON ENGINE MOUNTING HEIGHT NOMENCLATURE. THEN DESCRIBE THE ENGINE MOUNTING HEIGHT IN UNITS OF HOLES OR 0.75-inch INCREMENTS UP FROM LOWEST POSSIBLE MOUNTING.YOUR DESCRIPTION ABOVE OF MOUNTING HEIGHT IS UNCLEAR.

ENGINE DATA
2013 Suzuki DF60a
[Maximum permitted engine speed = ] 6300-RPM
Gear ratio 2.77:1

PRESENT PROPELLER FOR TEST DATA
SOLAS three-bladed 11-1/8-inch x 14-pitch [unspecified material and model]

ENGINE TRIM SETTING DURING TEST
Engine trimmed all the way down. The distance from transom to the leading edge of the gear case is 6-inches.

TEST CONDITIONS
[None given]

TEST DATA
RPM MPH
4000 20
4500 23
5000 27
5100 27.5

[RE-TEST with the engine trimmed out to distance between the transom and leading edge of the gear case increased to 8-inches from 6-inches]

TEST DATA
RPM MPH
5200 29 Note: engine hits rev-limiter

[The meaning of “modified” is further explained in unknown terms as a] bully net boat design.

[The test data was obtained while] driving from the bow of boat.

[No additional engine speed can be used without] spinning propeller.

I plan to [test again with a new propeller of] increase[d] pitch. Then next I will try a stainless [propeller].

[jimh]

Q1: what is “bully net boat design”?

Q2: what was the original model designation?

[No additional engine speed can be used without] spinning propeller.

Q3: what is meant by “spinning propeller”? The propeller must always be spinning in order to produce thrust to propel the boat.

[Nauti Native]

A “bully net design” is a modified hull that now has a front deck in which a forward console has been installed to drive standing on the bow of boat.

“Spinning the prop” means at 5200-RPM the propeller looses traction [ventilates] causing the engine to over-rev.
.
“Second hole” indicates where the [upper engine] mounting bolt [is placed].

[jimh]

The propeller ventilation is probably due to too much weight shifted to the bow causing the boat trim to be unusually raised in the stern.

Repeating earlier question: what was the original Boston Whaler model designation for this hull?

Repeating earlier request: please describe engine mounting height in units of holes or 0.75-inches above lowest possible position. In this case the engine may be mounted one-hole-up from lowest position.

[Nauti Native]

I had contacted Boston Whaler inquiring the original design , but unfortunately they tell me there was a period after1988 that records were unavailable.
My stencil # is 5B5290 .

The HIN BWC2124JE292

[Nauti Native]

Sorry “ One hole up “ is mounting position .

[Kapharms]

I had a similar problem with my 1977 Sport 15.

I ended up fabricating a plate to fix the [unspecified problem with] alignment [between two unspecified parts, perhaps the the existing engine mounting holes drilled in the hull transom and the engine mounting plate hole location created by the engine manufacturer].

[The plate that I designed and fabricated to remedy the mis-alignment] has worked [well to reduce or eliminate the “similar” problem] .
Ken

[Nauti Native]

Nicely done , Thank You !!
I don’t want to jump too far ahead yet , but have thought of a small 4” Hydraulic Jack plate . Obliviously to be able to lower when needed .