Help on 73 Larson Trihull "gimme boat"

[Nezlugh]

I inherited a 1973 Larson Shark 1650 with a 1973 Evinrude 115 hp motor. The history involves the original 125 Evinrude motor with power trim removed and this one mounted on it. I have repaired items as they have been found. The starter, solenoid, fuel tank, fuel lines, Teleflex helm to engine steering system, decarbed the engine and it now runs great on the muffs. I have taken it out and I am having trouble getting on plane. I have moved the thrust pin out and it just brings the bow up further. By reading these forums I believe I need to raise the motor without moving the motor back. The motor rests directly on the transom cap and I do have about an 1-1/2 " but I need more to get cav plate even with the keel. Does anyone have a good recomendation for a lift plate that does not move the motor back or at least minimally?

Thanks for having these forums to help the first timers.

 

[crb478]

Re: Help on 73 Larson Trihull "gimme boat"

You can loosen but not remove the lower bolts and then take out the top bolts. With the motor locked in the down position block up under the skeg and then raise the trailer in front with the jack. This will slide the motor up. Go slow and the replace the top bolts in the new holes. Tighten all the bolts resealing them with 4200 and then lower the jack. The take the boat out and see how it responds. Make sure you are still in deep enough to pump water to the powerhead.

 

[Nezlugh]

Re: Help on 73 Larson Trihull "gimme boat"

I was in the process of moving the motor up and took a break and looked up the parts lists on the evinrude web site. One thing I noticed is the plate on the bottom of the transom bracket the plate is positioned different than on mine. See the pic on mine. Is the straight side of the plate sopposed to be toward the housing or the transom. The trim catch will not reach the thrust pin in the closest adjustment. If this is turned around would it help bring the nose down and get up on plane better?

 

[Lion hunter]

Re: Help on 73 Larson Trihull "gimme boat"

The motor should be resting on the trim pin in the down position. Does it rest on the plate?

 

[tx1961whaler]

Re: Help on 73 Larson Trihull "gimme boat"

Another possibility is that there is 500 pounds of waterlogged flotation foam under the deck....

 

[Lion hunter]

Re: Help on 73 Larson Trihull "gimme boat"

True, there is no such thing as a free boat.

 

[Nezlugh]

Re: Help on 73 Larson Trihull "gimme boat"

The exhaust housing stops on the plate without locking on the thrust pin at it's lowest position. I will rotate the plate so it is straight side towards the transom this weekend and give it a try.

Does anyone have any pics of a Larson Trihull?

 

[Nezlugh]

Re: Help on 73 Larson Trihull "gimme boat"

I moved the motor up one hole and rotated the plate on the bottom of the transom mount. Took it out today with the thrust pin moved to the closest hole and the boat went right to plane.

Making good progress. It still is having a problem at idle, I have 2 carb kits to rebuild the carbs.

Any Tips!!!!!

Thanks for the help!

 

[ibmj54]

Re: Help on 73 Larson Trihull "gimme boat"

I have a 1973 larson trihull 1550, with a 135 johnson, last time in water was 89, took a year to rebuild everything. I was thankful engine only had minor repairs to it. It might be old but thankful for the age, do not have to worry about all the new computer crap on new ones... it cruises about 40 across water.