JET DRIVES SHOULD I FIT ONE?

[peterseafishing]

Jet Drives

 

Has anybody any experience with jet drives? I have a 25 foot fishing boat fitted with a 75 hp ford and a Sonic stern drive. I am overpowered for the Sonic stern drive and am looking at alternative drive systems. I am bringing the boat home for a full refit at the end of the season so will have time for major alterations. I would like to get away from the complex Z drive system I know that it would be easy to fit a Volvo stern drive but am worried on reliability. I like the principal of a jet drive and have been looking at Hamilton Jet drives as they seem to be the leaders. The hull is a planing hull and a may re-engine to a more powerful unit in the future. Any thought or information would be appreciated.

 

Pete

[Norm B]

Jet Drives

 

Has anybody any experience with jet drives? I have a 25 foot fishing boat fitted with a 75 hp ford and a Sonic stern drive. I am overpowered for the Sonic stern drive and am looking at alternative drive systems. I am bringing the boat home for a full refit at the end of the season so will have time for major alterations. I would like to get away from the complex Z drive system I know that it would be easy to fit a Volvo stern drive but am worried on reliability. I like the principal of a jet drive and have been looking at Hamilton Jet drives as they seem to be the leaders. The hull is a planing hull and a may re-engine to a more powerful unit in the future. Any thought or information would be appreciated.

 

Pete

From what I've heard they are not an economic proposition as they are very fuel thirsty compared to props.

[Fastd]

My only experience of jet drives is from my days of waterskiing when I was younger.

 

We had two jet drive boats , one powered by a ford mexico xflow engine and the other by a Rover 3 ltr v8.

 

Both boats were comparatively uneconomical with other inboard boats in the club. They also suffered from loosing power if the intake or jet tube was blocked in any way. The tolerance of the fit of the impeller to the tube is absolutely critical and it only took a small stone sucked up into the impellor to toally stop the drive despite there being no major signs of drive damage. Both boats had a spare impellor onboard as replacement was a regular essential.

 

Modern jet drives may be far superior to these older boats, but I personally would not consider fitting one to a sea going boat as a piece of bladderwrack or plastic bag over the intake filter leaves you limping home at 1 kt. Fine for a ski boat where shallow water and running them up on the beach was a regular occurance, but as a workhorse at sea I would not consider one.

 

Dave

[Toerag]

Jet drives really need to be designed into the boat as any cavitation renders them useless. As you only have a 75hp in a 25footer then this would probably not be an issue. They are good in shallow water, and good for maneouvreing, but as stated by others any problems with them are difficult to fix. As for getting the impellor intake blocked - that's much less of an evil than getting rope around your props. As for economical - look at the offshore 105 website and compare the speeds you get from the same engine using different drives. The other problem with a jet is you need a lot of room in the boat to fit the drive, a sterndrive needs much less space.

I have a volvo duoprop sterndrive in my MI21, and it's been reliable in the 1000+ engine hours over 3 years that it's done. The paint comes off the props, and I had a drive bellows go on me once, and prop seal go as well. When the prop seal went it ran quite happily with an emulsion of gear oil and seawater in the leg for months!