Frankenstein boat lacking in performance department

[etz]

I built a boat several years ago from a bare hull. It is a 2001 21 Larson SEI. It was completely stripped when I got it. It originally set up for Volvo drive,which was missing, so I replaced it with a Alpha. The motor itself runs great, but just doesn't have the performance I feel it should have. I know I am just putting out 200 hp, but it feels like more of an outdrive issue. I can only trim up for a second or two before you feel the prop loosing bite. Same thing when you make a sharp turn you just feel the boat stop pulling. I was able to bolt the alpha drive in the existing Volvo holes, so I don't know if it is set up correctly. Any suggestions?

 

[Bondo]

Re: Frankenstein boat lacking in performance department

I built a boat several years ago from a bare hull. It is a 2001 21 Larson SEI. It was completely stripped when I got it. It originally set up for Volvo drive,which was missing, so I replaced it with a Alpha. The motor itself runs great, but just doesn't have the performance I feel it should have. I know I am just putting out 200 hp, but it feels like more of an outdrive issue. I can only trim up for a second or two before you feel the prop loosing bite. Same thing when you make a sharp turn you just feel the boat stop pulling. I was able to bolt the alpha drive in the existing Volvo holes, so I don't know if it is set up correctly. Any suggestions?

Ayuh,... Welcome Aboard,... What motor,..?? Compression test, 'n tune up,..??

What gear ratio in the drive,..?? Prop condition,..??

Crawl under the back of the boat, 'n put a 4 to 6' straight edge, up against the keel line,....

If you see air, 'tween the hull, 'n bar, that's a Hook,...

If the bar rocks over a high spot, that's a Rocker,...

I suspect ya might have 1 or the other,...

'n while yer there, where on the drive does the bar intersect with the drive,..??

 

[etz]

Re: Frankenstein boat lacking in performance department

Ayuh,... Welcome Aboard,... What motor,..?? Compression test, 'n tune up,..??

What gear ratio in the drive,..?? Prop condition,..??

Crawl under the back of the boat, 'n put a 4 to 6' straight edge, up against the keel line,....

If you see air, 'tween the hull, 'n bar, that's a Hook,...

If the bar rocks over a high spot, that's a Rocker,...

I suspect ya might have 1 or the other,...

'n while yer there, where on the drive does the bar intersect with the drive,..??

The engine is a Merc 898 putting out about 200 hp on a good day. The prop is probably about a 19 pitch. As far as the keel it's pretty flat. When I measure from the keel to the prop centerline it's 9.5 inches. The biggest issue is the prop washing out in tight turns. It just looses all bight.

 

[achris]

Re: Frankenstein boat lacking in performance department

Check your 'installation height'.

With the drive trimmed down so the anti-cavitation plate is parallel with the hull, the anti-cav plate should be level with the bottom of the boat. If the drive/engine has been installed too high, the propeller will ventilate in turns. Which sounds like what you have.

Chris.....

 

[etz]

Re: Frankenstein boat lacking in performance department

Check your 'installation height'.

With the drive trimmed down so the anti-cavitation plate is parallel with the hull, the anti-cav plate should be level with the bottom of the boat. If the drive/engine has been installed too high, the propeller will ventilate in turns. Which sounds like what you have.

Chris.....

I ran the trim down till the anti-cav plate was parralell with the hull. It was in line with the hull. I could run the trim down further, this is the only place that it runs with out cavitation, full down. If I trim up more than a count of three, it starts washing out. When trimming, I hardly notice any changes in bow position or ride.

 

[Bondo]

Re: Frankenstein boat lacking in performance department

I ran the trim down till the anti-cav plate was parralell with the hull. It was in line with the hull. I could run the trim down further, this is the only place that it runs with out cavitation, full down. If I trim up more than a count of three, it starts washing out. When trimming, I hardly notice any changes in bow position or ride.

Ayuh,.... Change the Prop, 'n try it,...

 

[etz]

Re: Frankenstein boat lacking in performance department

Ayuh,.... Change the Prop, 'n try it,...

Suggestions? Would a 4 blade help?

 

[Bondo]

Re: Frankenstein boat lacking in performance department

Suggestions? Would a 4 blade help?

Ayuh,.... Donno,... I still suspect a hull issue, as pretty flat, ain't flat,...

Any prop of like pitch, will give ya a Test of the 1 on there,...