Props to my dealer and mounting question. Yamaha F70/1984 SE

[amazing grace]

So as I have told on here. I picked up an older SE early last spring. Removed the orig. 70 hp Merc and controls. Had hoped to find a newer used four stroke for it. Shopped for about six months but to no avail.

In calling around to dealers Tobler Marina out of Hayden Id. had a new F70 and shot me a great price. Told me to make a deposit and make payments as I could and it was mine. I did not want to buy new as I did not have the budget for it. But the price and payment plan worked so I went for it. About four or five months later everything was a go.

Took the boat to them about a month ago and they called last week and it was ready. Went over to pick up and do a lake test. All turned out great. Motor looks great. Ran great. Toblers shop did everything I asked. The tech that did the work took us to the lake which I appreciated. He was very good. I am very please with Toblers. They were all very professional. Listened, accommodated my needs and concerns. Gary, their service manager was great. Greg the finance guy was very helpful. Chris the sales guy was very laid back and helpful.


I do have a question and think I know the answer.
When we did the lake test and changed props a few different times I was a bit surprised that the SE did no pop right up on plane, Took maybe five or seven seconds to roll over and plane.

Once on plane we would trim it up. Seemed like it almost took no trim or very, very little. If we trimmed it very much it would start to porpoise noticably. Trim it back down and it would stop.

Let me back up just a bit. When I took the boat over and was going over the install I told the service manager I did not want it mounted too low. He said he would evaluate the hull and cavitation plate and mount it accordingly. We agreed.  I think it may be mounted a bit high though and that is why I am having the issues I mentioned above. The motor is mount a good 1-1/2" high from the bracket sitting down on the transom. They used the lower holes in the top of the bracket. I am thinking I should lower it to the other higher holes. Any thoughts?

Also I am not sure I have the right prop yet either.

Only have one hour on the clock so need to take it out for some more testing before doing anything. Thoughts? 

I may make an appointment to go back to the shop but that is a day trip to go have adjusted and drive home again. So I may do it myself.

[Fisherdv]

When testing those few different props did you take note of the max RPMS you were getting with each one at WOT?  That motor likes to rev, 6200-6300 max RPM. Of course, follow the break in procedure before going WOT for extended periods. This will significantly effect your hole shot and time to plane. You want a prop when loaded lightly will spin up to the max 6200-6300 range at WOT

[Fisherdv]

As far as helping determine the correct engine mounting height, give this a read. It's long, but very good info here

http://www.arimaowners.com/index.php?topic=13213.msg154956#msg154956

[Fisherdv]

On your test ride did you notice the prop blowing out on corners? Did the prop blow out while getting up on plane with motor trimmed down?

    As far as props go, from other members experience with the f70 on a 16 the SS PowerTech SCD-3 13pitch ($$$ expensive) or the 4-blade aluminum Solis props about $95-100 have had great success. Although I'm not sure if your year boat is 15'11" with a 7'6" beam Hope that helps some

[Yachter Yat]

  AG;  Your suspicion regarding the motor being too high may be valid.  I'm curios.......would you be able to run a straight edge of some kind along the keel and out to the motor, to see exactly how far above that, the bottom of the cavitation plate is sitting?  If you can, please let us know. 

Yat