Q1: What is the best way to increase the engine mounting height on a 1985 MONTAUK 17 where the lower holes were drilled higher than normal to use the blind hole mounting method on the original engine?
BACKSTORY
I currently have a 1985 MONTAUK 17 powered by a 2004 Yamaha 90-HP engine. I want to re-power with a Yamaha F90 four-stroke-power-cycle engine.
The engine mounting holes in the transom do not align. The older engine uses the [blind threaded] holes that are on the engine mounting bracket for the lower mounting bolts,
Due to the shallow engine splash well, I cannot [drill] lower [engine mounting] holes [in the transom].
The engine sits directly on transom. The [anti-ventilation plate] is even with bottom of hull.
On a website for FasseCo, I saw the use of a metal wedge to raise the engine higher than the transom.
Transom Engine Mounting Holes 1985 MONTAUK 17
Re: Transom Engine Mounting Holes 1985 MONTAUK 17
I have a 1987 Boston whaler 17 ft Montauk with a 1987 mercury 70 HP 2 stroke power cycle engine and all four engine mounting bolts go through the transom and are visible inside the boat. My engine was originally mounted resting directly on the transom but I was able to raise the engine 2 holes up.
Are your two lower mounting bolts visible in the engine well area or are they lag bolted directly into the transom?
Are your two lower mounting bolts visible in the engine well area or are they lag bolted directly into the transom?
Re: Transom Engine Mounting Holes 1985 MONTAUK 17
This has some information from the forum regarding mounting outboards https://continuouswave.com/ubb/Forum4/HTML/007774.html
Re: Transom Engine Mounting Holes 1985 MONTAUK 17
My 2 lower bolts are visible in motor splash well.
Re: Transom Engine Mounting Holes 1985 MONTAUK 17
What your describing is typical of outdated installation methods.
There is a standard mounting hole template for outboard engines. The modern recommendation for engine height on the Montauk 17 hull is 2 holes up, with the top bolt being in the 3rd hole counting down from the top.
As for the lower holes, the original installation used the "blind" holes of the engine bracket rather than the slots provided.
The remedy is for the bottom holes to be filled with plugs and epoxy and new holes to be drilled so the lower bolts are in the slots.
See the diagram below. The green holes should be drilled.
There is a standard mounting hole template for outboard engines. The modern recommendation for engine height on the Montauk 17 hull is 2 holes up, with the top bolt being in the 3rd hole counting down from the top.
As for the lower holes, the original installation used the "blind" holes of the engine bracket rather than the slots provided.
The remedy is for the bottom holes to be filled with plugs and epoxy and new holes to be drilled so the lower bolts are in the slots.
See the diagram below. The green holes should be drilled.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003
Re: Transom Engine Mounting Holes FAQ ANSWER
Hello Eleavitt. Your questions is a frequently asked question for owners of older Boston Whaler boats which have a shallow engine splash well.
There is an extensive answer given to your frequently asked question in the REFERENCE section of this website in the article called the FAQ.
Read the FAQ at
Q8: How does the engine mount to the transom?
https://continuouswave.com/whaler/reference/FAQ/#Q8
You should also read another article (which is pinned at the top of this forum) which answers you question in further detail. The article is
Transom Mounting Hole Layout for Shallow Splash Well
https://continuouswave.com/forum/viewtopic.php?f=7&t=5808
There is no need to use any sort of added metal plate to accomplish the raising of the engine mounting. That approach is ONLY useful on boats where there original transom height was made for engines with a 15-inch shaft length. The Boston Whaler c.1985 17-foot hull has a transom made for an engine with a 20-inch shaft length.
The hole layout on the engine mounting plate on outboard engines has been standardized since the 1980's. The Boating Industries Association or BIA published this layout, and it is still used, except on some very large, very heavy, newer engines of extraordinarily high power.
There is an extensive answer given to your frequently asked question in the REFERENCE section of this website in the article called the FAQ.
Read the FAQ at
Q8: How does the engine mount to the transom?
https://continuouswave.com/whaler/reference/FAQ/#Q8
You should also read another article (which is pinned at the top of this forum) which answers you question in further detail. The article is
Transom Mounting Hole Layout for Shallow Splash Well
https://continuouswave.com/forum/viewtopic.php?f=7&t=5808
There is no need to use any sort of added metal plate to accomplish the raising of the engine mounting. That approach is ONLY useful on boats where there original transom height was made for engines with a 15-inch shaft length. The Boston Whaler c.1985 17-foot hull has a transom made for an engine with a 20-inch shaft length.
The hole layout on the engine mounting plate on outboard engines has been standardized since the 1980's. The Boating Industries Association or BIA published this layout, and it is still used, except on some very large, very heavy, newer engines of extraordinarily high power.