1968 13-footer Nine Questions

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
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Joined: Sun May 09, 2021 5:55 pm

1968 13-footer Nine Questions

Postby Pslater » Sun May 09, 2021 8:02 pm

Q1: is there wood in the transom of a 1968 13-footer?

Q2: is use of square washers on engine mounting bolts proper?

Q3: does indentation of a engine mounting bolt washer into the gel coat indicate a problem in the transom?

Q4: does indentation of a engine mounting bolt washer into the gel coat mean additional support is needed on the inboard face of the transom?

Q5: does indentation of a engine mounting bolt washer into the gel coat indicate the mounting bolt was over-tightened?

Q6: does the static trim on the boat look right? (See Figure 1 below.)

Q7: should the boat be weighed?

Q8: should I check for ingress of water into the Unibond hull?

Q9: should I look for locations were water could enter the Unibond hull?

Fig. 1. Boat static trim.
trim_.jpg (9.5 KiB) Viewed 1428 times

Fig. 2. Drain outlet with flared brass tube eroded away.
drain_.jpg (11.51 KiB) Viewed 1426 times

Fig. 3. Lower engine mounting bolt head on inboard face of transom. Note cracked laminate at upper right.
bolta_.jpg (6.88 KiB) Viewed 1375 times

Fig. 4. Port upper outer engine mounting nut seen in extreme close up from overhead.
bolt2_.jpg (9.32 KiB) Viewed 1417 times

Fig. 5. Engine mounting with shim, showing engine mounted in lowest engine height position.
shim.jpg (32.04 KiB) Viewed 1416 times

Fig. 6. Engine mounting cockpit view.
engine2a_.jpg (30.38 KiB) Viewed 1378 times

I just acquired a [1968--always use four digits for years] 13-footer, a nice little boat. The 13-footer's primary use will be on 10,000-acre lake. The 13-footer runs fairly well, but the boat needs some tweaking. It seems to be in pretty good shape. There is very little spider cracking on the interior. Unless there is damage I can't see (like wet rotted foam) the hull seems to be solid. I want to insure the boat is sealed up.

I took it out for the first time yesterday. The boat engine is a 55 Evinrude. Top boat speed was 29-MPH speed over ground. I would expect more like 45 to 50-MPH. The outboard engine needs to come off. The mounting bolts need to be sealed.

The 13-footer need a new drain tube. The tube end is gone and the foam is exposed.

Thanks for any thoughts or advice on this old boat.

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Posts: 9501
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula

Re: 1968 13-footer Nine Answers

Postby jimh » Mon May 10, 2021 6:58 am

You seem completely new to Boston Whaler boats. You should read the REFERENCE articles on the 13-foot hull in the REFERENCE section of the WHALER section of the website. The website has a great deal more information than just the contents of this forum. You should also read the answers to the FREQUENTLY ASKED QUESTIONS. Here are links:

Website top page: http://continuouswave.com/

Boston Whaler boat top page: http://continuouswave.com/whaler/

Boston Whaler boat reference section: http://continuouswave.com/whaler/reference/

Boston Whaler boat reference section articles on the 13-foot hull: http://continuouswave.com/whaler/reference/13/

Boston Whaler boat reference section answers to Frequently Asked Questions:

The FAQ will answer many questions you have not yet asked but I anticipate you will have.

As for your nine questions:

A1: All Boston Whaler boats use embedded plywood to reinforce the transom.

A2: Engine mounting bolts on the inboard face of the transom always have washers. OMC often provided square washers.

A3: Indentation of an engine mounting bolt washer into the gelcoat and laminate could just be a result of over-tightening. A mismatch between the surface plane and the bolt orientation could concentrate forces onto one side, as can be seen in Fig. 2.

A4: A metal plate that spans between the two upper engine mounting bolts is often used to spread the load of the engine on the transom.

A5: Over-tightening of an engine mounting bolt can compress the transom laminate.

A6: Figure 1 is so small that assessment of the static trim is difficult, and the boat is not photographed at a good angle for assessing the trim. It looks a bit bow high. If that is a 55-HP engine, that is far above the maximum engine power of 40-HP rated for a 13-foot hull, and that static trim is bow-high is not surprising.

A7: Weighing a hull is one method to detect significant ingress of water, but the problem is really to know how much the hull weighed when new. See the FAQ answer at

A8: A careful visual inspection of the hull for any damage that could allow ingress of water into the interior of the Unibond hull is an appropriate method to assess the hull's integrity.

A9: See A8.

Pslater wrote:The 13-footer needs a new drain tube.
See advice in the FAQ for information about procedures for installation of new brass drain tubes at https://continuouswave.com/whaler/reference/FAQ/#Q12


In FIgure 5 a shim is shown that creates a change in the angle of the engine mounting. Usually a shim is used to permit more tuck-in or trim-in of the engine. This one seem to be mounted to create more trim-out, which generally is not necessary.

Since you plan to remove the engine, you should check the engine mounting hole locations on the transom. The engine appears to have the classic OMC and BIA engine mounting hole layout, so the transom mounting holes should be in the BIA layout. For more advice see the FAQ at Q8.

The stencil number of your 13-footer is 27054. That number is in the range associated with 1968 boats.

Posts: 9501
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula

Re: 1968 13-footer Nine Questions

Postby jimh » Mon May 10, 2021 12:52 pm

A simple method to assess the strength of the transom (assuming the engine has hydraulic trim-tilt in working order):

  • with the boat on a trailer, position the outboard engine so the gear case is set at about a 45-degree angle of tilt up;
  • move behind the engine gear case and take hold of the gear case at the skeg;
  • exert upward and downward pressure onto the engine gear case;
  • observe with care any movement of the transom caused by your pressure on the engine skeg;
  • with a solid transom there should be no deflection of the transom by force applied to the outboard skeg.