Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: Prop upgrade results, 1989 Montauk with 1998 Yamaha 90

Posted by Whalerbob on 06/15/14 - 9:24 AM
#1

Just wanted to thank everyone for the propeller advice and give some performance starts. I upgraded the aluminum prop to the 13.25" x 15 stiletto advantage and finally got it out on the bay yesterday and I'm very pleased with the results. I'm sure I had the wrong prop on the first place and all the nicks and dings weren't helping but before my max speed was about 31 mph @ 4500 rpm and yesterday I got 36 mph at 4700.
My engine is still mounted all the way down and the next step will be to re mount but not sure if I'll get to it before next winter. I've done all the research but one thing I'm still struggling with it's how to lift the engine. The cheapest I've found to rent a lift is about $40 a day, is that about right or is there a way to make a tripod out of 4x4 lumber?

Edited by Whalerbob on 06/15/14 - 9:26 AM

Posted by gchuba on 06/15/14 - 9:40 AM
#2

Whaler,
I had asked earlier how to remove my 235hp motor. Had a great idea come from a member (do not remember who). Lower your trailer tongue, set up a secure tri pod with lumber, attach the top of the motor (in my case with a 3 holed rigging attachment tool with an eyelet) with no/little slack, start raising the trailer tongue and the back of the boat lowers gracefully. Good luck.

Garris

For total removal done with a chain winch or come along at the top of the tripod

Edited by gchuba on 06/15/14 - 9:43 AM

Posted by Phil T on 06/15/14 - 9:50 AM
#3

Bob -

You can raise the motor without a hoist. Just need a friend, preferably someone tall/strong with long arms.

If the lower set of bolts are using the slots and NOT the blind holes. here is the procedure. If the bolts are blind, you need to remove the motor and re-drill the holes using the guide here:
http://www.whalercentral.com/articles...icle_id=82

Procedure for raising engines with lower bolts in the slots:
Boat and trailer on level ground. Wheels blocked front and back.
Lower the engine to vertical.
Place a block under skeg to protect it.
Loosen and remove top set of bolts.
Loosen just enough to allow motor to slide, NOT remove, the lower set of bolts.
Helper bear hugs motor to steady.
You go forward and use the trailer tongue jack to RAISE the bow so the transom goes DOWN. Raise bow to get top set of bolt holes to line up with transom holes you want.
Dry fit bolts in top to new position. Remove and insert marine sealant. Reinstall bolts and nuts and tighten.
Reseal bottom bolts around slot and tighten.

NOTES:

-Before you begin, make sure your tongue jack has enough travel. Adding blocking will help gain height.
-The sealant used may keep the engine tight to the transom when loosened. It may pop when you lower the transom.

Posted by Whalerbob on 06/15/14 - 1:47 PM
#4

Thanks all, it's currently mounted in the blind hole so I'm pretty sure I'll need to disconnect the wiring and controls to give me enough room to fill the old holes and drill the new ones.

I own a 2 ton come-along and floor jack so between that and the tongue Jack trick, lifting isn't the issue, just making sure it doesn't topple... I may have a support beam in my garage ceiling to hang it from but if not I might just eat the $40 and rent a lift but I'd want to plan ahead and make sure I can get it done in one day working solo.

2 more questions; 1) Will I be able to reuse the mounting bolts from the blind holes or will I need to purchase additional hardware? If so does anyone know exactly what size nuts / bolts I need? 2) Should I seal with M5200 or is there something else I should use?



Posted by Joe Kriz on 06/15/14 - 1:57 PM
#5

Bob,

You should be able to drill the RED holes in the diagram above if you have a 1989 model.
Layout the holes first inside and out to make sure you have room on the inside of the splashwell for the washers.

You will most likely need new lower bolts. These lower bolts will most likely be the same as the upper bolts which you won't need to change.

4200 is fine.

Posted by Whalerbob on 06/15/14 - 7:17 PM
#6

Joe,
I appreciate this but now I'm confused. After reading that article last winter, l walked away with the understanding I'd drill the green holes and mount 1 hole up and maybe go to 2 holes up.

After reading this I went back and re measured again and mine looks exactly like the diagram. I've got 10 3/4" from the top of transom to the bottom of the splash well. If I were to drill the red holes, the holes would be 1 1/8" oc from the bottom of the splash well so I'd have just enough clearance for the washers to clear. I agree that going in the other direction and drilling the green might be extreme but why not compromise and drill yellow?

I'm thinking the higher hole I can drill the less chance off water intrusion. I can't imagine any reason I'd want to mount the red hole with 0 holes up so why would I want to drill red, will this impact my choices/options when I re power?

Posted by Joe Kriz on 06/16/14 - 1:07 AM
#7

The Green and Yellow holes are for older Whalers.

About 1986, Whaler changed the splashwell of the 17' Montauk so the Standard BIA mounting pattern could be used.
The upper Black holes and the lower Red holes are the Standard BIA pattern.

Almost all boats today use the BIA standard mounting pattern which again are the upper Black and lower Red holes.

You are correct, you could drill the Yellow holes if that is what you choose.
You would not be able to lower the motor all the way down which you would probably never do anyway.

Posted by Whalerbob on 06/16/14 - 5:13 AM
#8

Thank you very much, yellow it is and I'll post the results of phase 2 when I get it done.

I know it's a big improvement in speed but I'm still scratching my head about only getting 4700 RPM. Is it possible I also need to make an adjustment to the throttle governor or is raising the height going to get me another 4000 and get me into the normal operating range for that engine?

Posted by Phil T on 06/16/14 - 7:41 AM
#9

Bob -

I recall the WOT range for the motor is 5000-5500 so your WOT rpm's are WAY low.

Is the prop new or new-to-you? Is the size stamped on it? (Are you sure it is what they say it is?)

The prop appears to be the correct size. The estimated WOT speed for a classic Montauk with a Yamaha 90 and that prop with just you, light gear, full load of fuel should be 40-42 mph @ 5400-5500.

With the bottom paint, extra battery, trolling motor and your current engine height, you are very close. Raising the motor would gain you 150-200 rpm's for each hole you go up.

I would suspect your tach is bad since your speed is close (assuming you measured average speed with a GPS.) but your RPM's are way off.

What is the idle RPM's showing on the tach?

Posted by Whalerbob on 06/16/14 - 8:56 AM
#10

I'm not sure if I'm sure of anything....
I was wondering if the tach it's working properly as well, I'll check idle RPM's next time out. My boat has bottom paint and relatively loaded, it was full of fuel, 30 crab traps, 6hp 4 stroke kicker, 2 group 27 AGM batteries... kitchen sink, etc...

If I can get to 40 mph I'd be thrilled.

Posted by Phil T on 06/16/14 - 12:08 PM
#11

You will NOT hit 40 with that load.

When I had 4 passengers (5 total) with luggage, I would get 34 at 4900.

It would be good to go out EMPTY and see how she does. It is an inexpensive way to test the prop/engine/tach.

If this is your typical load, you may want to prop it for that load. To do so, drop down to 13" pitch (as long as you stay with the exact same brand and style of prop.).