1970 Sakonnet E-TEC 90

Optimizing the performance of Boston Whaler boats
Skip Berry
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1970 Sakonnet E-TEC 90

Postby Skip Berry » Wed Aug 12, 2020 11:02 am

{in another thread, the performance of a 1970 SAKONNET re-powered with a 2020 E-TEC 90 engine became a new topic. That segment of the prior discussion has been moved to PERFORMANCE. --Moderator]

On a sea trial with the new E-TEC 90 on the 1970 SAKONNET with 11-gallons fuel and two adults (340-lbs.) aboard, using an aluminum three-blade propeller 13.2 x 19-pitch, in smooth water, the top boat speed was 39-MPH at a full-throttle engine speed of 5400-RPM.

I was a little disappointed with the 39-MPH at WOT. I was thinking something more like 42 or 43-MPH. Using the formulas from the propeller section I calculated a speed of advance of 48.6-MPH and a slip of 19.7.

Q1: What could account for such a high slip?

I only made one WOT run and did not change the trim. I will do a more thorough test soon.

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Re: 1970 Sakonnet E-TEC 90

Postby biggiefl » Wed Aug 12, 2020 11:28 am

With the engine that low, low 40's might be possible...like 41ish with a SS prop. I would mount the engine correctly and fill the blind holes.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

Skip Berry
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Re: 1970 Sakonnet E-TEC 90

Postby Skip Berry » Wed Aug 12, 2020 12:54 pm

14a.jpg
Fig. 1. Vertical height relation between keel and A-V plate.
14a.jpg (16.51 KiB) Viewed 11339 times


The anti-ventilation plate is currently 1/2-inch above the extended keel line. Raising the engine one or two holes would result in a distance of 1-1/4-inches or 2-inches above the extended keel line. Two holes up might make through bolting of the lower bolts possible. I'm thinking of using the tongue jack and blocking the skeg to raise the engine.

Q2: Is use of the trailer tongue jack a good plan?

Q3: should I lift the engine?

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Re: 1970 Sakonnet E-TEC 90

Postby biggiefl » Wed Aug 12, 2020 1:16 pm

I have used the tongue jack many times to adjust engine height.

[If you don't remove the engine from the transom and use the tongue jack method] [will you be able to] fill the blind holes that way?
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

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Re: 1970 Sakonnet E-TEC 90

Postby jimh » Wed Aug 12, 2020 1:29 pm

Skip Berry wrote:I was a little disappointed with the 39-MPH at WOT. I was thinking something more like 42 or 43-MPH

I only made one WOT run and did not change the trim.


Properly setting engine trim will affect boat speed at full throttle. I recommend you first re-test with more trim adjustments, and report more results.

Raising the engine mounting height should also improve top speed.

Skip Berry wrote:Q1: What could account for [a calculated SLIP of 19.7]?


A SLIP calculation of almost 20 is, indeed, a high value. Generally the calculated SLIP should be around 10 or lower.

I assume your data input to the calculator was:

RPM = 5400
RATIO = 2.0 (I assume you have the 20-inch shaft model)
PITCH = 19
MPH = 39

If the propeller pitch is incorrect, and the propeller were actually a 17-pitch, SLIP would be down to 10. Check that propeller pitch again.

Also, aluminum propeller blades tend to deflect under load, so the pitch will be reduced under heavy load.

The E-TEC 90 target engine speed for optimum power is listed in the REFERENCE section. See

E-TEC Recommended Engine Speed Range
http://continuouswave.com/whaler/refere ... neRPM.html

The E-TEC 90 engine optimum speed range is a bit lower than you have now; it is more like 5,000 to 5,200-RPM. A 19-pitch should get the boat speed to 42-MPH with SLIP=10 and RPM = 5200.

Also, if best performance is the goal, use a stainless steel propeller. Evinrude has a 13 x 19 pitch SSP propeller. Or try another 19-pitch from another brand. However, on a light boat and with only 90-HP, a good aluminum propeller should give decent performance.

Skip Berry
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Re: 1970 Sakonnet E-TEC 90

Postby Skip Berry » Wed Aug 12, 2020 4:09 pm

I will do a more thorough test with more trim adjustments and raise the engine one hole. Thanks Jim and Biggiefl.

My mistake. Mercury Service Bulletin.

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Phil T
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Re: 1970 Sakonnet E-TEC 90

Postby Phil T » Wed Aug 12, 2020 4:48 pm

aluminum three-blade propeller 13.2 x 19-pitch


After spending $8500-9,000 for an engine, the dealer slapped on a $140 prop. It's similar to buying a Lexus SUV and installing tires from a Big Wheel.

Owner recommendations for the 16'7 hull with a E-Tec 90hp include:

13.5 x 20” Raker
13-7/8" x 19” BRP Viper
13-1/4" x 19” SST +2
13-1/4" x 17” Turbo 1

*Note size only applies to specified make/model of prop. Engine mounted with top bolts in 4th hole down from the top.

My expectation is a WOT rpm of 5400 running light and solo with a speed of 43 mph, slip of 5%.
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Re: 1970 Sakonnet E-TEC 90

Postby jimh » Wed Aug 12, 2020 10:21 pm

PHIL--I like your analogy.

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Phil T
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Re: 1970 Sakonnet E-TEC 90

Postby Phil T » Thu Aug 13, 2020 4:13 pm

After looking at the parent thread, I see now the lower holes will need to be filled with hardwood plugs. Do not use a dowel since the wood grain will be in the incorrect orientation and future shrinkage will crack any gelcoat/epoxy repair.

To drill holes that break the surface of the splashwell, the lower holes are drilled as shown in this diagram.

Image
Fig. 2. Transom hole layout, BIA standard with modifications for the lower hole positions shown with color codings. See a follow-up post for explanation of what this diagram is illustrating.

When you measure, you will find the yellow (7-1/4") or green (6-1/2") holes will clear the splashwell.
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Re: 1970 Sakonnet E-TEC 90

Postby jimh » Thu Aug 13, 2020 5:56 pm

The diagram above is not particularly self-explanatory. The diagram shows four sets of lower holes. Only one set of the four is actually drilled in the transom. The standard hole layout is to drill the lower hole at an 8-inch spacing from the upper hole set. That position is shown by the RED holes. Drilling the transom with that layout is the STANDARD layout.

On older Boston Whaler boats with shallow splash wells, if the STANDARD layout is used, the lower engine mounting bolts will be buried in the internal foam of the hull. This problem is addressed in detail in the FAQ answer about engine mounting height. I recommend you READ THE FAQ ANSWER regarding engine mounting height in order to fully understand the problems related to engine mounting on older Boston Whaler boats.

Q8: How Does the Engine Mount to the Transom?
http://continuouswave.com/whaler/reference/FAQ/#Q8

Alternative hole layouts are shown in Figure 2 above. There are three options.

Drilling the transom as indicated by the YELLOW holes (at reduced spacing from the upper holes) will limit the engine mounting to one-hole-up or higher.

Drilling the transom as indicated by the GREEN holes (with even more reduced spacing from the upper holes) will limit the engine mounting height to two-holes-up or higher.

If the BLIND HOLE option is used--the engine mount bracket MUST have these blind bosses in the mount. The engine mounting height is fixed at lowest possible position.

Become very familiar with the transom hole layout options, and think carefully before drilling holes in the transom.

A somewhat different view of this same information is now provided at

Transom Mounting Hole Layout for Shallow Splash Well
viewtopic.php?f=7&t=5808

Skip Berry
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Re: 1970 Sakonnet E-TEC 90

Postby Skip Berry » Mon Aug 24, 2020 10:14 am

Thanks to Jim and Phil for your inputs. I raised the engine to two holes up. I achieved 42 MPH at 5350 RMM (12.7% slip). I was able to get to 42 mph by raising the trim. The elevated trim caused the boat to porpoise. Lowering the trim to stop the porpoising. I plan on keeping the engine two holes up. I have ordered SS bolts to through bolt the bottom bolts and will plug (no dowels) the bottom blind holes.

I get it when you compare my current prop to the tires on a Big Wheel. BTW my tow vehicle is a 2008 Lexus RX. Are you saying that my prop is a low quality aluminum prop or just that it is an aluminum, and not a SS prop?

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Re: 1970 Sakonnet E-TEC 90

Postby biggiefl » Tue Aug 25, 2020 11:17 am

A proper SS prop would probably get you closer to 45mph.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

Skip Berry
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Re: 1970 Sakonnet E-TEC 90

Postby Skip Berry » Mon Aug 31, 2020 11:31 am

I feel two holes up is the correct height. There is an improvement in performance. Time, more rigorous testing and a new prop should yield more definitive results. I haven't experienced any problems with ventilation during tight turns. With the engine mounted two holes up I was able to through bolt the bottom bolts. In place of washers I made two 1/4" thick backing plates. I plan on removing the lag bolts and filling the holes in the fall. Both the through bolts and the lag bolts are currently installed in the elongated bottom mounting slot of the engine.

Splash Well.jpeg
Splash Well.jpeg (82.96 KiB) Viewed 11003 times


E-TEC Mounting Bracket.jpeg
E-TEC Mounting Bracket.jpeg (87.11 KiB) Viewed 11003 times



Does anyone think I should leave the lag bolts in?

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Phil T
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Re: 1970 Sakonnet E-TEC 90

Postby Phil T » Mon Aug 31, 2020 11:58 am

Remove the lag bolts during the off season.

Remind us which prop (please include make, model, and size) you are you running.

How far out were you able to trim-out)(estimate 1/2, 2/3, 3/4, etc)to the point the hull stopped porpoising?
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Re: 1970 Sakonnet E-TEC 90

Postby biggiefl » Mon Aug 31, 2020 12:44 pm

It can't hurt but it is 2 more places for possible water intrusion.

PS...ditch the transom saver, not a good idea on Whalers, especially smaller ones.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

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Re: 1970 Sakonnet E-TEC 90

Postby Skip Berry » Mon Aug 31, 2020 1:49 pm

Prop: Evinrude Aluminum 13.2x19

This is just an estimate. The trim gauge has 5 marks, one indicating neutral, one up, two up, one down and two down. I started at two down. Porpoising started somewhere between two down and one down. A small reversal toward two down stopped the proposing.

I’d like to hear more on the transom saver. Why is it not a good idea?

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Re: 1970 Sakonnet E-TEC 90

Postby biggiefl » Mon Aug 31, 2020 2:19 pm

You are taking all the shock from the road to the trailer and reverting it to your lower unit which transmits it to your transom. They work fine for engines without PTnT and need ground clearance or say an aluminum hulled boat. I personally see no need for them on a quality made boat with PTnT. If you can run aground at 40mph and not hurt a Whaler transom, these are useless.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

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Re: 1970 Sakonnet E-TEC 90

Postby Skip Berry » Mon Aug 31, 2020 2:57 pm

Your thoughts on the transom saver make sense. My transom saver incorporates a strong spring. The power tilt compresses the spring between the two tubes. My understanding is this acts as a shock absorber to cushion road shock and lessen the angular torque exerted on the transom due to the weight of the raised engine. I do like your analogy of running aground at 40 mph. I haven't done that yet.

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Re: 1970 Sakonnet E-TEC 90

Postby biggiefl » Mon Aug 31, 2020 3:24 pm

I have not seen one with a spring, get us a pic. That may make sense and not be more stress on the transom.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

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Phil T
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Re: 1970 Sakonnet E-TEC 90

Postby Phil T » Mon Aug 31, 2020 4:12 pm

I recall the Evinrude E-TEC has a trailering bracket and an aftermarket support is not required. Other brands have a "support" bracket that is only to be used when engine is raised for service/storage.

Check your owners manual.

If I am incorect, use a product like m-y wedge (http://m-ywedge.com/order-today.html). Many engine manufacturer's have their own version at slightly higher prices.

I know a CW member who fabricated their own by buying a straight roller and drilling out the center and pressing in PVC pipe as a sleeve.
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Skip Berry
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Re: 1970 Sakonnet E-TEC 90

Postby Skip Berry » Mon Aug 31, 2020 6:32 pm

The Evinrude E-TEC does have a Trailering Bracket. I'm not an engineer, but it seems to me it does a great job of supporting the engine when trailered in the up position, but does little to protect the transom from the forces exerted by the moment arm of the raised engine. Bumps on the road when the engine is in the vertical position present a sheer force on the transom. With the engine raised the force of those bumps can be more of a twisting moment that might be more damaging to the transom.

While we are at it, what do you think is an adequate clearance for an engine to be trailered in the vertical position?

Here's a link to a spring supported transom saver. Not cheep, but IF it works well worth it.

https://www.amazon.com/gp/product/B001P ... UTF8&psc=1

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Re: 1970 Sakonnet E-TEC 90

Postby biggiefl » Tue Sep 01, 2020 10:18 am

That tiny spring probably does not do much.

Trailers do not have a lot of suspension travel--very minimal. I doubt the engine skeg is more than 10-inches above the ground on my boat trailer.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

Skip Berry
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Re: 1970 Sakonnet E-TEC 90

Postby Skip Berry » Thu Sep 03, 2020 10:39 am

The spring [in a transom saver that has been mentioned above] is actually quite strong. [The spring] is difficult to compress by sliding the two sections of the [transom saver] support together. In use [the spring] is partially compressed by lowering the engine with the power tilt.