1987 13-footer Engine Mounting

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
PMaine
Posts: 2
Joined: Mon Aug 20, 2018 10:04 pm

1987 13-footer Engine Mounting

Postby PMaine » Fri Sep 07, 2018 2:25 pm

I have a 1987 13-foot Boston Whaler boat, I am a new owner, and I am unsure of model.

The engine is a 1995 Yamaha 40-HP. I discovered that the [anti-ventilation plate] is roughly 2-inches below the hull.

From my research, these boats like the [engine mounting height to be such that the anti-ventilation plate will be located] about an inch above the hull bottom.

I can raise up the engine up about 1-inch if I use the current bolt locations. To mount the engine higher I will need to drill new holes.

How close to the top of the transom can the bolt holes be?

Currently the top bolt hole is roughly 2-inches from the top of the transom.

I am concerned that if I go any higher with the holes I may not have enough support for the engine.

Thanks for any replies.

User avatar
Phil T
Posts: 1068
Joined: Thu Oct 22, 2015 6:08 pm
Location: Was Maine, now Kentucky
Contact:

Re: Engine mounting 1987 13'

Postby Phil T » Fri Sep 07, 2018 3:15 pm

I think the previous owner has installed a long (20") shaft on the transom when a short shaft (15") is the correct size.

Is the engine resting on the top of the transom?

The standard BIA hole pattern is:

The top holes are 1 7/8" down from the top and 12 7/8 apart.

The lower holes to fit in the slots can be either 6 1/2, 7 1/4 or 8" below the top holes and 9 7/8 apart.

What do you have?
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

User avatar
dg22
Posts: 86
Joined: Sun Nov 29, 2015 4:06 pm

Re: Engine mounting 1987 13'

Postby dg22 » Fri Sep 07, 2018 3:20 pm

PMaine, I have a Panther tilt and trim unit with a 1973 50 hp Evinrude and the top bolts are 1 inch from the top of the transom and I've had no problems with the transom. I use big SS washers on the inside. My boat is a 1967 13' Whaler.

jimh
Posts: 6761
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 1987 13-footer Engine Mounting

Postby jimh » Fri Sep 07, 2018 4:26 pm

Most of your questions about proper engine mounting are frequently asked questions, and very detailed answers have been researched and written in the website’s Boston Whaler boat REFERENCE section.

Since you are a new Boston Whaler owner I recommend you read all of the answers to all the FAQ’s.

Since you haven’t identified the model designator for your 13-foot Boston Whaler boat, I recommend you read the multi-part article in the REFERENCE section on the 13-footer.

The organization of the website is very hierarchical and navigation should be easy. Here is a hyperlink to the REFERENCE section:

http://continuouswave.com/whaler/reference/

jimh
Posts: 6761
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 1987 13-footer Engine Mounting

Postby jimh » Fri Sep 07, 2018 4:31 pm

Of course you can drill holes wherever you like in the boat transom, but your caution regarding drilling holes too close to the transom top is very prudent and reflects the collective wisdom of the Boating Industry Association (BIA) that developed the guide lines for engine mounting location, the standard practices of all manufacturers that pre-rig their boats with engines, and the standard practice of all dealers who install engines.

I offer the same advice as in the FAQ and recommended by the BIA and represented by your own proper reluctance to drill holes any higher.

I recommend you carefully weigh any advice you get to ignore those guideline before you start drilling new holes.

jimh
Posts: 6761
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 1987 13-footer Engine Mounting

Postby jimh » Fri Sep 07, 2018 4:42 pm

If the boat under discussion is, indeed, a 1987 13-footer, then the transom height, if unmodified, should be for a 20-inch shaft length outboard engine.

PMaine
Posts: 2
Joined: Mon Aug 20, 2018 10:04 pm

Re: 1987 13-footer Engine Mounting

Postby PMaine » Fri Sep 07, 2018 7:01 pm

I did look through the reference and FAQ section, however I did not see anything that provided a spec regarding top bolt location.

The boat is a 1987 and it is a long shaft motor as it should be. I'll try to post some photos.

jimh
Posts: 6761
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 1987 13-footer Engine Mounting

Postby jimh » Sat Sep 08, 2018 7:46 am

PMaine wrote:I did look through the reference and FAQ section, however I did not see anything that provided a spec regarding top bolt location.


Please read the FAQ. The topic of engine mounting holes is discussed in great detail in the FAQ.

Below is a hyperlink to the FAQ:

http://continuouswave.com/whaler/reference/FAQ/

If you read the FAQ, you will find Question 9, whose topic is “What is the standard transom hole layout?”

The FAQ answer will give you the information you did not find when you “looked through the reference section and FAQ....”

To further help you find this information, below is a URL that links directly to Q9 on the FAQ:

http://continuouswave.com/whaler/reference/FAQ/#Q9

As I mentioned earlier in my initial reply, the FAQ would provide many answers for questions on the topic of engine mounting. Inasmuch as its seems the OP was not able to find any of this information, I will point more directly to Q8 in the FAQ, “How does the engine mount to the transom?”


Here is the hyperlink:

http://continuouswave.com/whaler/reference/FAQ/#Q8