trim angle

[Sallysea]

Still new at learning about my 01 34 sf with twin yanmars. I find that when I add trim and bring the bow down my speed at a given rpm picks up. This is the opposite of what happened with previous gas boats I have had. I don't have trim indicators, just rocker switches. It would appear to me that the issue is drag versus prop angle. I wonder if there is a sweet spot on trim that optimizes for maximum speed at a given rpm on plane? It might make it worth while to install trim indicators. Any thoughts out there?

At 3000 rpms, I pick up 1.5 knots (19 to almost 21) with trim.

[witeagle]

You have found the purpose of trim tabs. Aside from having a more comfortable ride, trim tabs improve fuel economy. Find the sweet spot - most speed at the lowest RPM = best fuel economy.

[Sallysea]

Thankyou for that, think I will install trim tabs with indicators, then I can go right to it when up on plane. Still odd to me, with outboards, trim corrected port/ starboard list but created drag in doing it and slowing the vessel down.

[The Good Life]

Sallysea
What engines does your 34 have? I have 6LPA 315 STP Yanmars on my 32 conbertible and wonder if that is what you have.

Pedro

[Sallysea]

I have the 350's. I think 6lp-ste. Love the boat, not sure what I am going to do if I need to work on the outboard side of the engines. Hire a very small mechanic?

[Dave K S]

The 350's would be 6lya-ste. Great motors.

[The Good Life]

Sallysea
If you have 6LP STE they are 315 hp and if you do have the 6LP 315 ste make sure that they can reach 4050 rpm because these 6LP motors are not happy if they are overprop. The other thing that you should do is change the coolant. You can use the Shell Rotella that is orange in color or the Texaco.
They are great motors but are very sensitive to those things

[Sallysea]

I can't find the engine data here at home. But I know when I had it surveyed, they were 350's. The vessel has 21X24 four blade props and I got 3800 out of it as max when I was on the bay. Have not pressed it since. But I doubt I could get 4000 out of it.
What's the deal with the specific coolant? Keep in mind this is my first diesel, I have been an outboard guy.

I tried to upload a photo of my son on our last halibut trip, think I got it.

[Dave K S]

Shell Rotella 15-40 is the oil that I use. The coolant is Texaco which I have not been able to find for the last 4 years. I have been using Prestone Dex Cool (orange color) Yanmar only uses Dex Cool antifreeze because of all the alluminum in the cooling system. It is not compatable with the green coolants. Your motor, 6LYA-STE, is rated at 3300 RPM Max. Make sure you can reach at least 3350 fully loaded. Make sure you know which engine you have because if you have 6LPA-STE they are 315 HP and you need to be able to reach at least 4000 RPM fully loaded or these engines will have a short life. As stated earlier all these motors will not last long if over proped. Yanmar tachs typically read about 100 RPM high. You should have them photo tached to be sure of the RPM's. If you can reach 3800 you should have no problems with 6LYA-STE's. You may even be able to add a little more pitch but make sure you reach at least 3350 I like to see 3400 min on my 6lya-ute's.
A good site to check out is boatdiesel.com. Lots of great info there.

[Sallysea]

I checked the motors today and they are 6lp-ste. Continuing ed on owning a new boat.